IB Biology Flashcards
Exam (419 cards)
1
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A1.1.1 Water as the medium for life
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Evolution of the first cell could not begin until temperature cooled enough for water to form and later, for the water cycle to begin. It is thought the first cells slowly evolved in the oceans. A solvent is needed for reaction to occur. First cells evolved a membrane to separate the water in the cytoplasm from the “ocean water”. Water is a solvent that: makes up fluid in cells, permits transport, essential to blood and other fluids in organisms, provides medium for life.
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A1.1.2 - Hydrogen bonds as a consequence of the polar covalent bonds within water molecules
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Covalent bonds - two atoms share electrons. Equal sharing of electrons creates a non-polar covalent bond. (neither has a higher density) Polar covalent bonds are unequal sharing of electrons. (different charges at each end) Ephemeral attraction = a hydrogen bond.
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A1.1.3 - Cohesion of water molecules
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Water molecules are highly cohesive. Cohesion = same molecules attracted to each other. Two water molecules bonded together = a hydrogen bond. At waters freezing point, molecular motion slows the the point where the hydrogen bonds become locked in place into crystal ice forms. Ephemeral hydrogen bonds between liquid water molecules is why water has surface tension. Surface tension = the layer of water molecules at the surface of a body of water which does not have water molecules above it. Water moves up a water column through xylem. Water then evaporates through transpiration and the water leaving has cohesion. There is then tension due to the low pressure caused by the evaporation so all water moves up the leaf. (occurs in stomata)
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A1.1.4 - Adhesion between the water and other polar substances
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Attraction between to unlike molecules due to hydrogen bonding = adhesion. Adhesion keeps the column within the water column from dropping down the tube. (same in capillary tubes) Capillary action in soil acts similar to capillary tubes. Water molecules adhere to the polar molecules making soil and water molecules move up through cohesion.
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A1.1.5 - The solvent properties of water
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Any solution that has water as the solve = an aqueous solution. Any substance that dissolves readily in water is hydrophilic. Any that does not is hydrophobic. Water can transport dissolved substances and many substances are an aqueous solution . hydrophobic (insoluble) are found in steroid hormones - passes directly through he plasma membrane. And proteins. Epidermal cells of leaves secrete a way that coats leaves (the cuticle) and is a water barrier - without this leaves would dehydrate as they are often exposed to the sun.
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A1.1.6 - The physical properties of water
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Table 1 come back and complete this
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A1.1.7 - The origin of water on Earth (HL)
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Most water remains as liquid. Our planet has a gravitational pull to retain water on or near its surface due its size. Some water that helps form our planet is trapped deep in the crust. Water molecules exist in 2 forms. Difference exists due to number of neutrons. “Ordinary” hydrogen atoms exist in water without any neutrons. “Heavy water” contains atoms with a neutron. This hydrogen is called deuterium. All bodies of water contain both of these, with the typical water being more common.The ratio of hydrogen to deuterium is similar tot he ratio on many asteroids. A theory is that the Earth used to only be made of magma but as asteroids struck the earth they brought hydrated minerals that became the earths crust.
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A1.1.8 - The search for extraterrestrial life
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Goldilocks zone = Earth being in position with the sun that allows water to be in its liquid form.
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A1.2.1 - DNA is the universal genetic material
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DNA provides long term genetic information for all organisms on Earth. Mutations occur in DNA and pass on to the next generation. DNA is universal providing evidence for our common ancestry. Sequences of nitrogenous bases are genetic messages/genes. Messages code for amino acids. Amino acids build proteins - cells identity + function is determined by the proteins ability to synthesize. every cell in a multicellular organism has the same DNA, but each uses only genetic info. that retains ofr that cell.
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A1.2.2 - The structure of nucleotides
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DNA + RNA are polymers of nucleotides. - has repeating units called nucleotides within the much larger molecule. Nucleotides = One phosphate group, one five-carbo monosaccharide (pentose sugar) and a nitrogenous base. Covalent bonds occur to produce the functional unit.
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A1.2.3 - Sugar to phosphate “backbone” of DNA and RNA
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The pentose sugar of one nucleotide is covalently bonded to the phosphate group of the next nucleotide. Nucleotides bond together to form a polymer as a result of condensation reactions forming covalent bonds between the sugar and phosphate group of the next. These bonds take a lot of energy to break so the nucleic acid polymer made of nucleotides is stable.
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A1.2.4 - Nitrogenous bases within nucleic acids
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4 bases in RNA + 4 in DNA. RNA has uracil instead of thymine. RNA = ribose, DNA = deoxyribose.
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A1.2.5 - The structure of RNA
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RNA = nucleotides bonded tog. in specific sequences. Nucleotides join through a condensation reaction between the pentose sugar of 1 nucleotide + the phosphate group of the next nucleotide. This reaction releases a water molecule. (If RNA molecule contains 322 nucleotides, 321 molecules of water were produced in its synthesis - 321 condensation reactions formed.)
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A1.2.6 - The structure of DNA
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RNA = single chain of nucleotides. DNA = 2 strands of nucleotides connected through hydrogen bonds. Two bases making up 1 rung = complimentary base pairs.
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A1.2.7 - Distinguishing between DNA and RNA
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DNA + RNA = linear polymers w/ sugars phosphates + bases. Note the differences in the two on the table. Ribose has a molecular formula of C₅H₁₀O₅, Deoxyribose = C₅H₁₀O₄. When removing 1 oxygen from the alcohol (-OH) group, it shifts the formula by a lot. mRNA = synthesized from a gene. IT leaves the nucleus and represents the genetic info. necessary to make a protein. tRNA- when a specific protein is synthesized, specific amino acids must be added to the amino acid chain in an order. tRNA transfers the correct amino acid into a growing chain of amino acids. rRNA - created ribosomes. ATP single- nucleotide nucleic acid. Produces a chemical energy. When a muscle contracts, ATP molecules are used as an energy source for the movement.
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A1.2.8 - The importance of complementary base pairing
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Allows for templates of DNA to be made so the DNA can be synthesized.
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A1.2.9 - Storage of genetic information
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DNA stores its info. in its bases. Every three bases is called a triplet codon - w/ a meaningful piece of info. There are 4 diff. nucleotides that can be arranged in triplets. The odds of Dan containing any 1 triplet is 1/64. This shows the info. is limitless and enormous. The likelihood that 2 DNA molecules are identical as a result of random chance is nearly 0.
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A1.2.10 - Genetic uniqueness
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Genetic code has remained unchanged due to evolution. Evolution changes DNA sequences slowly but always uses the same mechanisms of genetic coding.
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A1.2.11 - Directionality of RNA and DNA strands (HL)
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The 5’ and 3’ = fifth and third carbon atoms. DNA has 2 strands antiparallel. - One runs 5’ to 3’ other is 3’ to 5’. Both are synthesized 5’ to 3’. When RNA/DNA is formed, 1 nucleotide at a time is added to the molecule. A new strand will always begin with the 5’ end.
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A1.2.12 - Purine-to-pyrimidine bonding
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When bonding, a purine is bonded to a pyrimidine and results in a consistent strand. Purine = double ringed, pyrimidine = single ringed. This makes a very stable helix shape with three dimensions.
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A1.2.13 - Efficient packaging of DNA molecules
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DNA is long so there is a packaging solution. Histones are proteins. DNA wraps itself around 8 histones w/ an additional histone holding the structure tog. This results in a nucleosome. DNA extends from one to the other then stack up in an organized pattern, coiling other proteins in a condensed shape. The overall shape is a chromosome. Humans have 46 of these.
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A1.2.14 - The Hershey-Chase experiment
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Hershey and Chase made use of radioisotopes w/ radioactive isotope labelling. They can be detected w/ in molecules. One culture had radioactive phosphorus 32. This virus produced detectable P32. Another was sulfur 35. This was present in the outer coat of the viruses produced. Dan does not include suffer and suffer was only detectable in the protein shell of the virus because 2 of the 20 amino acids that can be present in protein contain sulfur. they were each allowed to infect the bacterium E. coli. The E. cold infected with the sulfer had no radioactivity inside the cell. the P had radioactivity detected. DNA contains P and not S so they concluded DNA was the genetic material.
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A1.2.15 - Chargaff’s rule
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Scientists believed protein was responsible for genetic traits. Chargaff developed a research technique to show proportions of nitrogenous base types found in DNA. The results showed there is almost the same ratio of adenine to thymine and gunanine to cytosine. DNA contains the same # of adenine as thymine + guanine and cytosine. This is known as Chargaffs rule. Shows the tetra nucleotide theory is false, as all would ne equal, but there was not equal proportions.
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A2.1.1 - The formation of carbon compounds
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Larger mass has more gravity than smaller. The number of impacts on Earth’s surface began to decrease 4 billion years ago. Free oxygen was not present, if it had been it would have formed a layer of ozone in the upper regions of the atmosphere - blocking UV light. It is thought Earth’s early atmospheric components coupled w/ high surface temperatures, lighting w/ gradual cooling which resulted in formation of many carbon compounds. This is not evident today.
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A2.1.2 - Functions of life
Metabolism includes all chemical reactions that occur w/in the organism. Due to this, cells can convert energy from one form to another. Growth may be limited but is always present. Reproduction involves hereditary molecules that can be passed to offspring. Responding to stimuli in the environment allow organisms to survive. Homeostasis = maintenance of a constant internal environment. Using sources of compounds w/ many chemical bonds that can be broken down to provide energy is the basis of nutrition. Excretion is essential as it allows chemical compounds that are harmful to be released. Cell theory has 3 main principles - all organisms are composed of one or more cells, cells are the smallest unit of life, all cells come from pre-existing cells.
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A2.1.3 - Evolution of the cell
The third principle of the cell theory = cells may only come from other pre-existing cells. Protocells = appear is pre-biotic environment so more complex cells could form. A series of them. + physical processes have to occur for a cell to evolve. 1. Synthesis of small carbon compounds from abiotic molecules. 2. Small organic molecules joining from large-chain molecules (polymers) 3. Polymers becoming contained by membranes, creating a protective homeostatic environment around the polymers - separate from surroundings. 4. Development of self-replicating molecules - inheritance and control can occur.
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A2.1.4 - Inorganic to carbon compounds
Inorganic compounds do not contain carbon (unless CO2) Carbon compounds contain carbon are complex. These make life possible. The Miller-Urey experiment was to stimulate the conditions thought to be on Earth + to determine if these gases could interact to produce the first stage in the evolution life. The apparatus was charged w/ the simple inorganic compound CH4, NH3 and H2 representing Earth's early atmosphere. Heat was used to produce water vapour which rises to the chamber holding the inorganic compounds. 2 electrodes in this chamber produce 7,500 volts + 30 amps of electricity, representing lightning. Cold water flows into the condenser to allow condensation of gaseous compounds. a sample is collected for analysis. Miller identified several simple organic molecules known as organisms - hydrocarbons and amino acids. Primordial soup was found (sea of simple organic molecules) It is believed that this is invalid as they believe the first atmosphere of our planet formed slowly over extended periods of time from volcano gases. This means our chemical properties on Earth are not the same as before and gases today do not contain NH4/CH4. Instead H2O vapour. CO2, SO2, + CO + HS4. These would produce a non-reducing environment and the one in this experiment produced a reducing environment.
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A2.1.5 - The formation of vesicles
Membrane provides a barrier between the inside of the cell w/ surrounding environment. Fatty acids were thought to be present in early Earth. These were present in water + has polarity. 1 end = hydrophilic other = hydrophobic. When large #'s are placed in H2O, they organize into small cell-sized double-layer bubbles called vesicles. Development of a boundary around a vesicle = compartmentalization = was necessary for formation of first cells. As they progressed this compartmentalization became evident w/in the boundary allowing specialization of functions in diff. regions inside the outer protective fatty acid bilayer.
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A2.1.6 - RNA as the first genetic material
Short RNA molecules = assemble spontaneously from nucleotides, can form copies of itself so a type of genetic material, demonstrates the ability to control chem. reactions so acts as an enzymatic role. These allowed the functions necessary for the formation of early cells. Ribozymes (type of RNA) is active in catalysing activities - faster development of peptide bonds. Because RNA is so much simpler than DNA it is thought to have been the first genetic and controlling compound of a living cell.
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A2.1.7 - Evidence for a last universal common ancestor (LUCA)
- universal genetic code by DNA + shared by all cells. - over 300 genes common to all cells. - same building blocks for both DNA + RNA in all cells. - common molecular processes w/in all cells (replication of DNA + production of proteins) Hypothesized that other life forms having distinctive characteristics other than these have evolved but are not present today due to unsuccessful comp. w/ LUCA + its descendants.
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A2.1.8 - Dating the first living cells and LUCA
Charles Darwin utilized the concept of common ancestry. Everything traces back to a single ancestor, the LUCA. Earliest evidence of life on Earth comes from fossils. Most are hard parts (bones/teeth) but some can be footprints etc. Estimated that life occurred earliest on Earth 3.5 billion years ago. An accurate means of dating fossils involve radiometric techniques - based on the half-life, length of time it takes for a half a radioactive isotope to change into another stable element. Fossils contain isotopes. SO by measuring the amount of an isotope in a fossil + comparing it w/ the amount taken up when the organism lived, we can determine the age of the fossil. This is absolute dating of a fossil's age. Relative dating is not as exact as absolute darting. It utilizes sediment layers of Earth + index fossils.
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A2.1.9 - Hydrothermal vents and the evolution of the LUCA
A hypothesis suggests that the location for the origin of life on earth is around hydrothermal vents. Lot's of life exists at the bottom of the ocean even w/ no sunlight. This gives credibility to the hypothesis that the earliest life forms could have formed deep in the ocean around hydrothermal vents. Evidence for LUCA at hydrothermal vents = very old fossilized precipitates originated here, commonality of genetic sequences in the organism near the vents - likely single ancestor, presence of mineral-rich environment necessary for chem. reactions, presence of H2 and CO2 results in the reducing environment essential for carbon compound formation.
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A2.2.1 - Cells and the functions of life
Cytology = studies all facets of the cell. Cell theory = all organisms are composed of 1 or more cells, cells are the smallest units of life, all cells come from pre-existing cells.
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A2.2.2 - Cells and the microscope
Cells need to be observed w/ high magnification + resolution. Light microscopes use light passing through to form an image, electron microscopes use electrons passing through a specimen to form an image. Magnification = measured size of image/actual size of specimen.
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A2.2.3 - Advanced microscopy
SEM uses a beam of electrons to scan the surface of a specimen. TEM aims a beam of electrons through a thin section of a specimen - inner structure is viewed. Freeze fracture = rapid freezing of a specimen followed by physically breaking the specimen apart. This reveals a plane through the sample that is examined. Cyrogenic electron microscopy enables an image to be formed using computer enhancement that shows three-dimensional framework of proteins involved in the function of a cell. Light microscopy involves fluorescent stains and immunofluorescence that combine w/ specific cellular components. The condenser on a light microscope posses a lens that directs light rays from the light source through the specimen.
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A2.2.4 - Structures common to all cells
All cells posses certain common structures including - DNA as their genetic material, a cytoplasm composed of mainly water, a plasma membrane composed of lipids that surrounds the cytoplasm. For new cells to be formed from pre-existing cells, they must store and transfer info. DNA fulfils this role due to tis ability to form large molecules from nucleotides. The mainly water part of the cytoplasm = cytosol which contains all ingredients for the cell to function. The plasma membrane encloses the cell + protects its contents w/ 2 layers of lipids combined a s a bilayer.
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A2.2.5 - The prokaryote cell
Prokaryotic cells = small + bacteria cells. Their cell wall is composed of a carb-protein complex called peptidoglycan. Some has an additional layer of a polysaccharide outside the cell wall called the capsule. This allows adherence to structures like teeth, skin and food.
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A2.2.6 - The eukaryote cell
The comparison between prokaryotic and eukaryotic cells are - prokaryotic cells = DNA in a ring form w/ out protein, DNA free in the cytoplasm, no mitochondria, 70s ribosomes, no internal compartmentalization to form organelles. Eukaryotic cells = DNA w/ proteins as chromosomes, DNA enclosed w/ in a nuclear envelope (nucleus), mitochondria is present, 80s ribosomes, internal compartmentalization present. Both have an outside boundary that always involves a plasma membrane, both cells conduct all functions of life, DNA is present in both.
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A2.2.7 - Unicellular organisms
Metabolism = sum of all chem. reactions that occur w/ in an organism. Growth = The development of an organism. Reproduction = ability to produce offspring. Response to stimuli = As the environment changes, the organism adapts. Homeostasis = maintenance of a constant internal environment. Nutrition = the ability to acquire the energy + materials needed to maintain life. Excretion = the ability to release materials not needed into the environment. Movement = ability to change position. Unicellular have unique ways of carrying out life functions compared to multicellular organisms.
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A2.2.8 - Different types of eukaryotic cells
All 3 cell types contain mitochondria that posses cirstae, a matrix + a double membrane. In all 3 the mitochondria functions in the proaction of ATP.
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A2.2.9 - Atypical eukaryotes
Some multicellular fungi produce filaments called hyphae. Phloem sieve tube have a specialized function allowing transportation w/ in a multicellular plant. These elements have one walls ww/ pores + has min. cellular components. These can only remain alive w/ the help of companion cells - maintain a close connection w/ sieve tube elements.
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A2.2.12 - The origin of eukaryotic cells (HL)
Endosymbiotic theory = about 2 billion years ago a larger cell w/ a nucleus did sexual reproduction + engulfed a smaller prokaryotic cell that could produce energy, these cells developed a symbiotic relationship forming 1 single organism, the smaller engulfed cell went through multiple changes to become a mitochondrion. The larger cell helped the bacteria prokaryote by protecting it + providing carbon compounds. Much more evidence for this exists.
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A2.2.13 + A2.2.14 - Cell specialization + multicellularity
Compartmentalization was an important process in the development of the cell. All cells in multicellular organisms have the same genetic info. For specialization + differentiation to occur, mechanisms have developed that control + coordinate gene expression.
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A2.3.1 - Characteristics of viruses
Viruses are all small and fixed, contain a nucleic acid (RNA or DNA), enclosed by a boundary composed of a protein - capsid, do not contain cytoplasm inside the capsid, possess few enzymes. They infect a host cell - the capsid allows attachment to the host cells. The host cell is the cell that a virus uses to carry out its metabolic +reproductive functions. Some viruses contain a capsid w/ a specialized protein that allows the genetic material of the virus to penetrate the host cell membrane. Some viruses have an envelope outside their protein boundary from the host cell's plasma membrane.
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A2.3.2 - Structural diversity in viruses
Electron microscopes are needed to view viruses. Viruses show great variation in shape + structure. They can be thread, polyhedral or spherical.
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A2.3.3 + A2.3.4 - The life cycle of viruses
Viruses must have a host cell. To reproduce: attach to a site on a host cell, then incorporate their genetic material into the cytoplasm of the most cell, then use the host cell's processes to produce components of themselves, then assemble the viral components unto new functioning virus entitles, finally release the new virus entities into the host cell's environment. Bacteriophages - viruses which infect bacteria. The lytic life cycle is new virus particles are released by the lysis or rupturing of the cell membrane by the enzyme lysozyme. Lysis only occurs after the production of fully functional virus particles - virions. The lysogenic cycle: DNA of bacteriophage combines with the bacterial DNA to form a prophage. The next generation carries the prophage in their genome.
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A2.3.5 - The origin of viruses
The diversity of viruses suggest several possible origins. They share an extreme form of obligate parasitism as a mode of existence so the structural features that they have in common could be regarded as convergent evolution. The genetic code is shared between viruses and living organisms. Virus first hypothesisL viruses originated before cells. Regressive hypothesis: viruses were once small cells that became parasites of larger cells. Escape hypothesis: DNA and RNA escaped from larger organisms such as bacteria.
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A2.3.6 - Rapidly evolving viruses
Influenza and HIV are two types of virus which display rapid rates of evolution. HIV goes through genetic drift at a very rapid pace. When treating these caused by rapidly evolving viruses they may start to resist treatment.
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A3.1.1 - Variation between organisms
Organisms are categorized based on morphology (physical appearance) Each category is called a taxon. Largest taxon is a "domain" + contains all the specific taxa - KPCOFGS. When variation can be placed into categories it = discontinuous. when there is a range = continuous.
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A3.1.2 - Species as groups of organisms
Linnaeus had difficulty identifying p;ants so he put known living organisms and placed them into categories. This morphological classification is still used today such as Elephas maximus.
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A3.1.3 - The binomial naming system
Binomial nomenclature = system of naming organisms by using 2 names. First name is always capitalized while second is lowercase + genus + refers to the species. Both are written in italics or underlined when written. Species in the same genus have similar traits.
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A3.1.4 - Biological species
Biological species concept - to be classified in the same species, they must be able to breed together + produce fertile offspring. The challenges w/ this include the fact of some organisms reproducing asexually so do not breed, some hybrids produce fertile offspring. Other definitions include the ecological niche of an organism, genetics types of molecules an organism produces, lineage for extinct species.
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A3.1.5 - Distinguishing between populations and species
Speciation = process of population being operated into 2 groups that cannot reproduce together. 1 can have mutations or other pressures causing it to evolve differently. There are now 2 species that have a common ancestor.
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A3.1.6 - Diversity in chromosome numbers
Different species have different chromosomes numbers. Diploid cells always have an even number of chromosomes as it must be divisible for offspring.
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A3.1.7 - Karyotypes
Karyogram = representation of chromosomes in a cell arranged in a format - placed in order of size + shape. Shape depends mainly on the position of the centromere. Cells are stained on a glass slide, photomicrograph is obtained during metaphase, images are cut out + separated, images of each pair of chromosomes are placed in order of size + shape. Evolution of chromosome 2 = scientists have made 2 hypotheses as to why humans have 46 and chimpanzees have 48 chromosomes = a complete chromosome disappeared / 2 chromosomes from an earlier common ancestor fused to become 1 chromosome. To test this, we can examine 2 characteristics that help identify a chromosome: shape + banding patterns. An X shape chromosome = metacentric. If 1 centromere is at 1 end + arm is much shorter than the other it is an afrocentric shape. All primates have both. A hypothesis is that human chromosome 2 arose from the fusion of shared ancestor chromosomes 12 + 13. Chromosome 2 was compared to the chimp. 12 + 13 and the 2 acrocentric non-human chromosomes were placed end to end + have a similar length to the human chromosome. The centromeres lined up w/ 12 but not 13. This refutes the hypothesis. DNA w/ in the centromere is called satellite DNA. Telomeres are caps on tips of chromosomes that contain repeating sequences of DNA. There is telomeric DNA in the centre of human chromosome 2. This is not supposed to be in the centre but only at the tups and is present where the 2 chromosomes would have fused. This provides evidence.
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A3.1.8 - Unity and diversity of genomes
Variations of the genome causes mutations. a variation involving 1 base is called a single nucleotide polymorphism. Only 5% of SNPs are functional (make a difference) Most will not affect the phenotype. The Human Genome Project aimed to determine the order of all bases in the human genome. Genome = all genetic info. of an organism. Organisms in the same species share most of their genome but variations give some diversity.
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A3.1.9 - Eukaryote genomes
A major difference between genomes is their size: quantity of DNA in the nuclei. Certain species need genes to do specific things. A specific way to compare genetic diversity in eukaryotes is to look at mitochondrial DNA.
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A3.1.10 - Genome sizes
Genome size can indicate complexity but there are exceptions to conclude this is not a reliable indicator.
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A3.1.11 - Whole genome sequencing
Phylogenetics = comparison of whole genome sequences. Organisms that share similar genomes are more closely related than others that aren't. Next-generation sequencing techniques = mix of lab hardware, chem. markers that allows for private citizens to get their genomes sequences. Some countries have this as illegal. Personalized medicine is info. about a persons genetic makeup being applied to an individual when prescribing treatments. Knowing more about how a patient's genome might cause new proteins to be produced in their cells/ trigger certain genes to be turned on/off may lead to breakthroughs in medical treatments. Another use of the human genome is production of new medications - they must find beneficial molecules that are produced naturally in healthy people, find out which gene controls synthesis of a desirable molecule, copy that gene + use it to instruct synthesis of a molecule in a lab., distribute the beneficial therapeutic protein as a new treatment.
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A3.1.12 - Difficulties with the biological species concept
Parthenogenesis = process of females producing a young w/ out a male. In plants a similar process occurs = vegetative propagation (strawberry plant sends out a runner that takes root near original plant. Bacteria reproduces asexually using binary fission. Bacteria undergoes horizontal gene transfer. An assumption of the concept of a species is all members of the species has a common lineage from common ancestors. This is the basis of the tree of life concept. Xenologs/jumping genes are sequences of DNA that is found in common w/ another species than the one it is found in.
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A3.1.13 - Chromosome number as a shared traut
A female horse +make donkey can mate and produce a mule. Mules cannot mate to make more mules. Because mules are not fertile, the mule is not a new species but an interspecific hybrid. This is because a female horse has 64 chromosomes while a donkey has 62 creating 63 in the offspring which is nit divisible by 2.
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A3.1.14 - Dichotomous keys
Dichotomous key is used to establish which taxa an organism belongs to.
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A3.1.15 - DNA barcoding
Genetic sequences are obtained from organisms + given a number that is matched against a database of sequences that are previously identified + named organisms. A DNA barcode is a short sequence of DNA inside an organism cells that can be used to quickly identify the species. Environmental DNA is collected from the environment rather than the organism. The DNA is amplified using a technique called polymerase chain reaction. Scientists studying zones w/ pollution want to know the biodiversity and if it's affected. This is measured by counting the number of species present. Species can be used as bioindicators which are so sensitive to pollution that their presence indicates a lack of pollution, and conversely. Disadvantages of using environmental DNA includes it only giving an indication of the presence/ absence of a species, not the size. DNA does not indicate if it is from a li ing organism or a dead one. Certain chemical incompatibilities exist w/ processing of soil samples due to substances in the soil interfering w/ the sequencing process - inaccurate results possible.
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A4.1.1 - Evolution
Darwin came up w/ the theory of evolution by natural selection. Evolution is defined as the process of cumulative change in the heritable characteristics of a population. DNA evidence provided new support for natural selection + led to the modern synthesis theory. Darwin + Wallace's theory replaces a previous idea by Lamarck. This was that organisms acquired characteristics through their lifetime + passed them on to their offspring.
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A4.1.2 - Biochemical evidence for evolution
Our DNA includes genes that go back to common ancestry w/ fish. This explains during the development of human embryos we have slits in our necks (fish). A phylogenetic can be used.
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A4.1.3 - Selective breeding
Selective breeding = breeders choose desirable traits + breed them together. Breeders choose which animals will reproduce + which will not = artificial selection.
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A4.1.4 - Homologous and analogous structures
Homologous structures = derived from the same body part of a common ancestor. Pentadactyl limbs are a common ex. for this. Analogous structures = same function but different body part so no common ancestor. Wings are a common ex. of this.
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A4.1.5 - Convergent evolution
Analogous structures provide evidence for evolution. Convergent a + divergent evolution refers to not only an entire organism but also to physical features. Convergent evolution = diff. species look / behave more like each other over time potentially allowing them to exploit similar niches + developing analogous structures.
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A4.1.6 - Speciation
New species are formed due to speciation. For ex. the island iguana populations - they have evolved differently over years as they have had to adapt to differing environments. When they can no longer interbreed like the mainland iguanas + the island iguanas, a speciation split has occurred. Extinction happens when the last individuals of a species die out. (Wooly mammoth, dodo, T. Rex)
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A4.1.7 - Reproductive isolation and differential selection
Some species may be prevented from reproducing due to a barrier between them - temporal geographical or behavioural. Over time 2 populations will face selection pressures so will change. Eventually they will change into 2 separate populations. This is reproductive isolation. An example of this is the Bonobos living south of the Congo river while the chimpanzees live on the north + east of the river. Due to the difference in habitat, food and enemies their traits differ from each other. Chimps. are more aggressive bonobos are more peaceful.
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A4.1.8 - Allopatric and sympatric speciation
When a new species forms from an existing species due to a barrier = allopatric speciation. (geographical speciation leads to this) Sympatric speciation is a new species forming from an existing species living in the same geographical area. This can be caused by temporal / behavioural isolation. Temporal isolation = incompatible time frames that prevents gametes from touching, Ex. if female parts of flowers of 1 population of plants reach maturity earlier than realize of pollen of another, 2 cannot create offspring. Behavioural isolation is differing behaviour isolating it from the rest of the pop.
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A4.1.9 - Adaptive radiation
Adaptive radiation = similar but distinct species evolved rapidly from a single species. This happens due to variation w/ in a pop. A niche is a position / role in a community. Through natural selection + presence of reproductive isolation, a new species can evolve.
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A4.1.10 - Barriers to hybridization, and hybrid sterility
when a sperm fertilizes an egg, its chromosome 1 needs to be compatible w/ the eggs chromosome 1. Each gene's position, its locus needs to match for the genetic info. to contribute to the offspring. Behavioural isolation happens when 1 populations lifestyle is not compatible w/ another pop. Females of 2 species will not be attracted by courtship rituals performed by males of a diff. species. Hybridization will then not take place + their gene pools will not mix.
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A4.1.11 - Abrupt speciation in plants
Polyploidy = a cell contains 3 or more sets of chromosomes. This can arise during production of sex cells. Much more common in plants than animals. In plants this can lead to more vigorous plants that produce bigger fruits or food storage organs. In animals this is normally fatal but some fish and frogs demonstrate polyploidy. But the change causes the offspring w/ the original pop. to be impossible so speciation occurs. An advantage to polyploidy is that it can allow sterile hybrid plants to be fertile. W/ additional genetic material, plants can produce seeds + pollen w/ the same number of chromosomes which can produce fertile offspring. Extra genetic material can give plants an advantage over other plants. Abrupt speciation = hybridization + polyploidy can allow speciation to be very quick. The new organism has a diff. chromosomes number from its parents so is reproductively isolated.
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A4.2.1 - Biodiversity exists in many forms
Biodiversity = variety of life in an area, A healthy coral reed = high level of biodiversity - burned forest does not. Ecosystem diversity = diversity from largest viewpoint. Great Barrier Reed is an ex. of 1 of the most ecologically diverse locations. Species diversity or species richness is the number of diff. species in a community. Species evenness is a measure of the relative abundance of each species in the community. Populations w/ greater genetic diversity are more stable.
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A4.2.2 - Has biodiversity changed over time?
Even though extinction is very high, fossil record suggests there are more species alive today than ever. There are still many more species to be discovered.
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A4.2.3 - Human activities and the rate of species extinction
Extinction caused by humans = anthropogenic species extinction. An extinct species Case study 1: North Island giant Mao lived in New Zealand. They were hunted to extinction so this is anthropogenic extinction. Case study 2 : Caribbean monk seals were killed for its oil.
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A4.2.4 - Human activities and ecosystem loss
Case study 1: mixed dipterocarp forests were dominated
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A4.2.5 - A biodiversity crisis
IPBES provides guidance for reliable scientific policymakers, IUCN was continuously updated for its list of threatened species.
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A4.2.6 - Causes of the biodiversity crisis
Human pop. growth affects include; over-exploitation of resources, hunting, deforestation, monoculture, pollution, increased pest species, invasive species, urbanization, spread of disease.
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A4.2.7 - conservation of biodiversity
In situ conservation efforts - managing natural areas. Ex situ conservation efforts- managing 1 or more species outside their natural area. There is reqildign, reclamation of degraded landscapes, and establishment of nationals parks that is an attempt at ex situ conservation. Ex situ efforts include animal husbandry, artificial insemination. Botanic gardens help promote biodiversity. Seed banks safely store seeds. Animal tissue banks - germplasm stores reproductive cells of various threatened species. second type is somatic tissue + used for DNA research + possible cloning.
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A4.2.8 - The EDGE of existence programme
First IUCN Red list is consulted. A score is generated from this list to how endangered the species is. Then is evaluated for its unique evolutionary history. Done using DNA sequencing info.
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A3.2.1 - The classification of organisms
Classifying organisms helps us discover ancestries + see which species are related to + how all species are connected.
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A3.2.2 - Difficulties in classifying organisms
Difficulty of Linnaeus's system is the concept of hierarchy whereby a smaller category is placed w/ in a bigger category. If an organism belongs to a genus it must be in the sam family as all other organisms in that genus. The more that organisms are discovered, the more often the hierarchy does not work. Introgression = process which hybrids form over many organizations but have an equal share of the original two species genetic info. there is an unequal contribution from each species. Some variety in wolves can be explained by introgression with coyotes.
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A3.2.3 - Classification using evolutionary relationships
Classifying organisms using molecular differences in protein sequences + DNA = molecular systematics. Phylogeny is the study if evolutionary past of a species. Comparing the phylogenetic tree shows the evolutionary relationships between species by showing which species developed from a common ancestor. The advantages of a system = not based on contrived categories. Evolutionary relationships can looked at w/ clades / monophyletic groups. - a group compromising the most recent common ancestor of that group = its descendant. A clade compromise just 1 species or can be made up of multiple species.
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A3.2.4 - Clades display common ancestries and shared characteristics
Cladistics is a natural classification of taxa grouping. Primitive traits (plesiomorphic traits) have similar structure + function + evolved early in history. Derived traits (apomorphic traits) have similar structure + functions have evolved more recently in the form of modifications of a previous trait. The resulting classification shows that all the organisms descended from the earliest common ancestor being studied have the primitive trait but in smaller clades some would have derived traits. In another clade, that considers more species, a primitive trait could be considered a derived trait. By comparing these characteristics, the quantitative results indicate which organisms have undergone a more recent split.
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A3.2.5 - The evolutionary clock
Differences in polypeptide sequences accumulate over time as mutations occur. We can count differences in homologous molecules from 2 related species to quantify similarities + differences through DNA hybridization. A strand of DNA is taken from a species + a homologous strand from another species which are then fused tog. using enzymes. Another method uses quantitative biochemical data as a molecular clock to estimate time of speciation events. We cannot think of this as an actual clock as mutations can occur at varying rates so we only have averages.
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A3.2.6 - Constructing cladograms
A cladogram is used to represent the findings of cladistics in a visual way. A node is the place where a speciation event occurred. The larger clade is divided into a sister group + an outgrip which is less closely related to others in the cladogram. The base where other species branch out is called the root. The tips of the diagram = terminal branches. Cladograms are open for falsification so it changes.
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A3.2.7 - Using cladograms
node= split in cladogram showing a hypothetical common ancestor, root = base of cladogram showing common ancestor of all clades, terminal branch = end of a branch representing most recently evolved of the organisms in the clade. Closer to the root, the further back in the past the cladogram represents + fewer derived characteristics the organism will have.
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A3.2.8 - Cladistics and reclassification
Analysis of zones of DNA markers such as nuclear ribosomal internal transcribed spacer region has revealed that the old system was not monophyletic. Paraphyletic is species on seperate branches. Moving the branches of the tree of life + reclassifying a taxon in a new branch changes the species' circumscription.
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A3.2.9 - Three domains of life, not two
Top of classification hierarchy = 3 largest groupings for organisms = domains - Archaea, Eubacteria, Eukarya. Archaea = single-celled organisms distinct from bacteria. Extreme conditions archaea = extremophiles including thermophiles, methanophiles, halophiles. Eubacteria = domain which we find bacteria such as in yogurt to taste good helping the intestines work properly but are some that might give infection. Eukarya = all other life other than Archaea and Eubacteria from yeast cells to large organisms such as blue whales + trees. Separating archaea from other prokaryotes bacteria exists due to differences in the subunit of their ribosome (16s rRNA), metabolic reactions carried out by archaea that no bacteria can perform. Ways in which archaea read DNA to produce RNA + proteins for RNA, some physical features of archaea are diff. from bacteria such as types of molecules used to build their cell membrane + cell wall.
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B1.1.1 - The variety of compounds containing carbon
Carbon-carbon covalent bond is two carbon atoms haring electrons. Hydrogen, oxygen, nitrogen, carbon, phosphorus, are all common w/ in molecules of living organisms. These are found in carbohydrates, proteins, lipids, and nucleic acids. They often form covalent bonds w/ carbon + each other. Covalent bonds for hydrogen = 1, Oxygen =2, Nitrogen = 3, Carbon = 4, Phosphorus = 5.
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B1.1.2 and B1.1.3 - Condensation and hydrolysis
Macromolecules = smaller molecules 0 monomers. Digestion breaks down macromolecules as a result of chem. reactions called hydrolysis reactions. This breaks covalent bonds between monomers. Resulting monomers are then absorbed into the bloodstream + circulated to body cells. After entering the cells monomers are built up into macromolecules again. This involves forming covalent bonds in condensation reactions. The "R" notation indicates amino acids could be any of the 20 diff. possibilities. When a portion of the carboxyl group of 1 amino acid becomes oriented near the amine group of the other, stress is placed on the -OH of one amino acid + the H+ of the other. This results in the covalent bonds breaking + an -OH + H+is released but still contains a pair of electrons which form a new covalent bond. Whenever this occurs between 2 amino acids, the new bond = a peptide bond. The reaction is catalyzed by an enzyme. Foods are chemically digested in the alimentary canal - which are hydrolysing enzymes. In a hydrolysis reaction water is split.
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B1.1.4 - Monosaccharides
Ribose + deoxyribose are monosaccharides + central components of the nucleotides RNA + DNA. Ribose = a pentose monosaccharide - meaning the carbon backbone is composed of five carbons. Chemical formula for this is .... Glucose is a hexose monosaccharide as its carbon backbone is composed of 6 carbons. Its chem. formula = .... Glucose is produced in photosynthesis + used in respiration. Glucose is used to make polysaccharides some for structural purposes, some for energy storage. Glucose is polar covalent and has: molecular stability, high solubility in water, easily transportable, yields a great deal of chemical energy.
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B1.1.5 - Polysaccharides and energy storage
In amylose, carbon 1 is bonded to carbon 4 of the adjoining glucose. When hundreds of glucose molecule are bonded by 1-4 linkages its resulting molecule will be linear but in a helix shape. The 1-6 linkages are typical in amylopectin. Starch contains both of these. This has low solubility so can be easily stored. Glycogen is a polysaccharide made of glucose monomers.
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B1.1.6 - Cellulose as a structural polysaccharide
Glucose beta + alpha are very similar but have reversed atoms on their right side. This affects the polymers formed by each side.
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B1.1.7 - Conjugated carbon molecules
Glycoproteins on the surface of red blood cells determine a persons ABO blood type. Red blood cells can have two possible types of glycoproteins on their plasma membranes. The two proteins, A and B are called antigens. a person cannot receive an A or B blood antigen unless they have genetically inherited that glycoprotein.
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B1.1.8 - Lipid solubility
Lipids are substances in living organisms that dissolve in non-polar solvents but are only sparingly soluble in aqueous solvents. Lipids include its, oils waxes and steroids. (non-polar due to the non-polar covalent bond)
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B1.1.9 - Triglycerides and phospholipids
One glycerol molecule can link three fatty acid molecules or two fatty acid molecules and one phosphate group. Triglycerides contain one glycerol molecules and three fatty acid molecules.
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B1.1.10 - Properties of fatty acids
Saturated fatty acids: single bond. High melting point due to this. Solid at room temperature. Monounsaturated fatty acids: one double bond. Lower melting point + oil at room temperature. Polyunsaturated fatty acids: more than one double bond. Low melting point + oil at room temperature.
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B1.1.11 - Adipose tissue
Adipose tissue - cells that store fat in form of triglycerides. The properties of triglycerides make them suited to long-terms energy storage functions. These can be used as thermal insulators to body temperature and habitat.
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B1.1.12 - Phospholipid bilayer
Amphipathic are molecules which have both hydrophobic and hydrophilic regions.
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B2.1.1 and B2.1.2 - Membrane structure
Phospholipids and other lipids naturally form continuous sheet-like bilayers in water. The hydrophobic hydrocarbon chains that form the core of a membrane have low permeability to large molecules and hydrophilic particles, including ions and polar molecules, so membranes function as effective barriers between aqueous solutions.
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B2.1.3 - Diffusion across cellular membranes
In diffusion, particles move from higher concentration to lower concentration. Oxygen is lower in concentration inside the cell compared to outside. Oxygen diffuses unto the cell as a result. CO2 diffuses in the opposite direction as it is produced in the cell. They move between the phospholipid molecules of the membrane so their diffusion occurs easily.
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B2.1.4 - Membrane proteins
Membrane proteins have diverse structures, locations and functions. Integral proteins are embedded in one or both of the lipid layers of a membrane. Peripheral proteins are attached to one or other surface of the bilayer.
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B2.1.5 and B2.1.6 - Membrane transport
Passive transport does not require cellular energy, active transport does. Passive transport: a substance moves from an area of high concentration to lower. Movement occurs along concentration gradient. Kinetic energy is the source. Active transport: substances move against the concentration gradient so energy expenditure occurs. Equilibrium is not reached but is reached in passive transport. Osmosis - passive transport. occurs across a partially permeable membrane. Hypertonic solution: higher concentration than hypotonic. Isotonic: equilibrium is achieved. Most cell membranes have aquaporins which allow water to pass through. Facilitated diffusion: involves carrier and channel proteins. Carrier proteins change shape to carry substances. Channel proteins: more pores which molecules of appropriate size and charge can move past.
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B2.1.7 - Active transport and pump proteins
Active transport: requires work to be performed so energy is used (ATP) The sodium-potassium pump is an important example of active transport - uses ATP to move ions against a concentration gradient which is important in nerve cells - neurone so animals can respond to stimuli.
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B2.1.8 - Membrane permeability
Size and charge decide how early a substance can move across a membrane. Facilitated diffusion an active transport allow selective permeability in membranes. Permeability by simple diffusion is not selective and depends on size and hydrophilic/hydrophobic properties of particles.
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B2.1.9 - Glycoproteins and glycolipids
Glycolipids: when phospholipids have carbohydrate chains attached to them. Glycoproteins: cell membrane proteins which have chains of carbohydrates attached to them. These two are important for cell identification and cell adhesion. The characteristics of human blood types, A, B and O are the result of carbohydrate chains. Carb chains allows the body to decide which cells belong to it and which cells are from outside. (transplants) Rejection of the organ means the body's immune system is attacking the foreign cells. Glycocalyx is a thin sugar layer made of carb chains attached to proteins which cover the cell. This coating allows for cell adhesion, cell to cell recognition, and reception of signalling chemicals.
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B2.1.10 - The fluid mosaic model
Integral proteins: completely penetrate lipid bilayer, control the entry + removal of molecules from the cell. Peripheral proteins: supports membrane stability. Glycoproteins: composed of carb chains attached to peripheral proteins, play a role in recognition of like cells and are involved in immune responses. Cholesterol: helps to regulate membrane fluidity and is important for membrane stability.
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B2.1.11 - Fatty acids and membrane fluidity
Unsaturated fatty acids in lipid bilayers have lower melting points, so membranes are fluid and therefore flexible at temperatures experiences by a cell. Saturated fatty acids have higher melting points and make membranes stronger at higher temperatures. (know the example of adaptions in membrane composition in relation to habitat)
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B2.1.12 - Cholesterol and membrane fluidity
Cholesterol affects the plasma membrane fluidity =. They act to stabilize membranes at higher temperatures and maintain flexibility at lower temperatures. Plant cells have cell walls to stabilize the membrane so do not need cholesterol.
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B2.1.13 - Bulk transport and membrane fluidity
Endocytosis allows macromolecules to enter the cell. Exocytosis: allows molecules to leave. Endyocytosis occurs when a portion of the plasma membrane is pinched off to enclose macromolecules or particles w/ in a vesicle of the cell. This allows a change in shape. Exocytosis: normally begins w/ the ribosomes of the rough ER + progresses through a series of steps: 1. Protein produced by the rough ER enters lumen. 2. Vesicle carrying the protein fuses w/ the cis side of the Golgi apparatus. 3. As the protein moves through the Golgi apparatus it is modified + exists on the trans face inside another vesicle. 4. Vesicle w/ the modified protein inside moves towards + fuses w/ the plasma membrane resulting in the secretion of the contents from the cell.
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B4.2.1 - Species and ecosystems
Niche = unique role a species place in a community. Abiotic factors (non-living) affect the organisms habitat. These include sunlight, soil, pH + temp. Biotic factors (living) include relationships.
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B4.2.2 - Obligate anaerobes, facultative anaerobes and obligate aerobes
Tolerance = how well a species reacts to the presence of something in its environment. Chem. transformation of nutrients into energy is aerobic respiration. nutrients to energy w/ no oxygen is anaerobic respiration. Obligate anaerobes = no tolerance to oxygen. Facultative anaerobes carry out both anaerobic + aerobic respiration. Obligate aerobes need oxygen to convert nutrients to energy. Hypoxia = oxygen reduced. Anoxia = absent oxygen.
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B4.2.3 - Photosynthesis
The green pigment in organisms is chlorophyl used for photosynthesis. This is found in plants. Most organisms need sun to get energy. Autotrophs = organisms that make their food from inorganic substances such as photosynthesis. They can also be eaten by others so are producers.
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B4.2.4 - Holozoic nutrition
Heterotrophs can't make their own food. Holozoic nutrition = way of getting nutrients by ingesting the organisms. These are called consumers.
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B4.2.5 - Mixotrophic nutrition
Organisms can be autotrophic + heterotrophic have mixotrophic nutrition. This is useful when sunlight is low. The genus Euglena is made up of protists that have photosynthetic pigments but also can ingest food so this is mixotrophic. Obligate mixotrophs need both systems to thrive. Facultative mixotrophs can survive on one system but use the other as a supplement.
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B4.2.6 - Saprotrophic nutrition
Saprotrophs = live on non-living organic matter, secreting digestive enzymes + absorbing the products. Fungi + bacteria are saprotrophs called decomposers.
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B4.2.7 - diversity of nutrition in archaea
Living thins categorized into 3 domains: Bacteria, Archaea + Eukarya. Archaea use photosynthesis, chemosynthesis, heterotrophic nutrition. Chemoautotroph = produces its own food using chem. reactions w/ no sunlight. Gets the energy through chemosynthesis.
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B4.2.8 - The relationship between dentition and diet
Primates = Hominidae. Incisors = front teeth, canines to the side of incisors, premolars in the middle then molars in the back. Large incisors = mostly plant or fruit. Microwear = small abrasions on a tooth's surface from chewing reveal the food they eat.
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B4.2.9 - Adaptions of herbivores and plants
Aphids are insects which use stylets. Others use mandibles. Cows = ruminants - swallow grass before chewing. They then regurgitate it and chew more - chewing the cud. Herbivory - feed on plants. Thick bark/ thorns help plants defend themselves. Phytotoxins = plant poison which defends. Animals however evolve to neutralize the toxins. Colonies of microbes proliferate and can cope w/ the poison.
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B4.2.10 - Adaptions of predators and prey
Behavioural adaptations - Teamwork - pack hinting Hughes the chance of defeating an animal. There is an established relationship. Known leader etc. Pursuit predators rely on speed to outrun its prey. Endurance also works which is persistence hunting. May behaviours are instinctive/ in DNA. Physical adaption include camouflage or aposematism - informs predators they are poisonous w/ unusual dramatic colours. Chem. reaction = venom/ poison.
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B4.2.11 - Harvesting light
Trees use a canopy underneath is the understory where shorter trees are. Shrubs are shorter + frost floor is smaller non-woody plants. Lianas are vines that grown into the canopy to obtain more light. When seeds germinate they seek light and bend towards it. Liana however bends towards shade. Lianas are a direct competitor or trees (minerals sun + space) Epiphytes also take advantage of light through trees canopy or understory but these roots are not in the soil. Semi-epiphytes spend their life in a. tree w/ no roots till they push their stems downwards to reach the ground + grow roots. Herbaceous plants (herbs) do not produce a woody stem.
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B4.2.12 - Ecological niches
Fundamental niche = potential niche it could inhabit. Realized niche = actual niche it inhabits. Diff. due to comp. w/ other species.
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B4.2.13 - Competitive exclusion
Competitive exclusion = no 2 species can occupy the same niche. If they do coexist both populations will decrease. Interspecific comp. means 2 or more species. When these grow tog. they do significantly worse than alone.
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B4.1.1 - What is a habitat?
Habitat - place where organisms live. When more than one species have similar requirements the place is a community if multiple lives. Habitats provide basic requirements - shelter, food water oxygen, light. Living organisms do not live in isolation but share habitats + impact another.
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B4.1.2 - Adaption to the abiotic environment
Sand dune grass species lives on + creates sand dunes. Sea data = drought resistant + have a large shallow root system. W/ long roots helping reduce transpiration. they produce nodes + rhizomes near their base, above the sand line. When covered by blowing sand, the asexual growth shoots are stimulated + produce shoots above the sand. Sexual reproduction is accomplished w/ production of seed heads resembling a true oat plant. Mangrove tree species - grows along saltwater. The prop roots extend above the water line. there lots above the water line also absorb air. The air oxygenates the root tissues which are below the water line buried in mud. The roots below the water line filter salt out of the water so the tree has fresh water. Red ,mangroves adapted to changing water levels so the tangles root growth under the trees provides a protective habitat for many marine animals. Red mangroves produce a fruit containing a seed that germinates + begins to grow before falling from the parent plant. The young plant is called a propagule - this eventually falls from the tree + floats in the water below. After absorbing the water the propagule orientates itself in shallow water w/ its roots downwards + begins early root growth. A shoot w/ early leaves grows from the opp. end. This is an adaption for plant dispersal in a marine environment.
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B4.1.3 - Abiotic variables
Any abiotic factor (non-living) can act as a limiting factor is it is outside the tolerance zone of an organism. Some organisms developed special adaptions that extend their tolerance range w/ in their habitat. Many catfish can take in oxygen through skin - live in oxygen-poor habitats.
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B4.1.4 - Limiting factors
Limiting factor (abiotic/biotic) limits a population size. It limits the abundance of a species.
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B4.1.5 - Coral reef formation
Corals = a symbiotic relationship between coral polyps + microscopic algae (zooxanthellae). Both organisms require suitable growth conditions. Small size of the ocean SA populated by coral reefs is an indication that the combo. of all the right abiotic factors for these symbiotic species is rare. Table on 331.
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B4.1.6 - Terrestrial biomes
A biome is a large geographical area that contains communities + plants adapted to living in that environment. Biomes are often dominant vegetation type that is found w/in the biome. Biomes are created by varying conditions of precipitation + temp. can be plotted on a graph.
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B4.1.7 - Biomes, ecosystems and communities
Plants + animals found in similar biomes that are geographically separated will have diff. genetic backgrounds.Morphology + physiology will be similar but organisms in a community will have little genetic similarity. Convergent evolution is the reason for this. Similar species that live w/in the same ecosystem are often genetically related as often they are a result of adaptive radiation. Table on 335.
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B4.1.8 - hot deserts and tropical rainforests
The saguaro cactus has thick waxy skin as waterproof + covered in bristles as a defence. Also a long taproot that sends down to retrieve deep water + massive shallow root system to absorb rainwater. The fennec fox has vascular ears that help dissipate heat. Large helps help locate small prey animals. The kapok tree - strong foundation from buttress roots that extend above ground. Poison-dart frogs - developed highly toxic chemicals in their skin as a result of their diet of poisonous insects. Evolved to have bright colours + body patterns to warn predators.
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B3.3.1
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B3.3.2
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B3.3.3 - Antagonistic muscle pairs and titin
Muscles use connective tissues - tendons to attach 2 bones. One bone is an immovable anchor (origin) while the other (insertion) moves as a result of the muscle contraction. Two muscles accomplish opp. movements are antagonistic to each other. Muscles use a force to help w/ relocation as a result of the spring-like action of a protein called titin - an immense protein that has multiple folds allowing it to act like a spring. When sarbomers shorten during a contraction the 2 sides of each sarcomere move towards the centre creating a spring-like tension in titan that is released when the muscle relaxes. This allows each sarcomere of the muscle to undergo a contraction again. titan also holds myosin fibres in place in the sarcomere + prevents muscle fibres overstretching.
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B3.3.4 - Motor units
Nervous sytem controls skeletal muscle contraction. Every movement requires many electrical impulses in the brain + terminating at synapses called neuromuscular junctions. These junctions are a type of synapse where a chem. message sends into the muscle tissue - stimulating a contraction. Neurons that carry these messages are called motor neurons. Each motor neuron has a set number of muscle fibres that controls to - motor unit. If a low intensity contraction is needed a low number of motor units is activated by the brain.
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B3.3.5 - skeletons as levers and anchor points
Arthropods have an exoskeleton made of chitin. Skeleton is on the outside + has a hollow skeleton. Many individual bones of skeletons act as levers. A lever is a rod able to rotate about a fixed point known as a fulcrum (joint).
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B3.3.6 - synovial joints
Synovial joints occur where 2 bones need to move against each other + notable for wide range of motions that they allow. (elbow, knee, shoulder, hips) Head of a demur forms a ball that fits into. rounded socket in the pelvis bone - ball-and-socket joint. Entire joint is encased by a membrane that contains a lubricant - synovial fluid. Hip joint is encircled by tough fibrous ligaments that hold bones in place but allow movement. Numerous muscles exist controlling movements of the hip joint each w/ tendons that connect the bones. Table on 316.
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B3.3.7 - Range of motion
Goniometers measure a range of motion of a joint.
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B3.3.8 - antagonistic muscle action
External intercostal muscles are the first muscles seen looking from the outside. Beneath are the internal intercostal muscles. When external intercostal muscles contract, the rib cage is pulled upwards + out. This occurs during inspiration. Antagonistic internal intercostal muscles move the ribcage down + inwards during expiration. Movement of the ribcage + diff. orientation of the muscle fibres permit stretching of the muscle layer that is not being contracted. When external intercostal muscles contract the expansion of the ribacage results in stretching of the internal intercostal muscles. this stretches the titan fibres in each sarcomere of the muscle layer creating potential energy that can be used for the next contraction of internal intercostal muscles.
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B3.3.9 - The need for locomotion
Most animals rely on location for a variety of reasons - food, finding a mate, escaping predators/migrating. Table on 319.
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B3.3.10 - Swimming adaptions
Dolphins whales +seals all descended from ancestral species that once lived on land. Their internal anatomy is adapted to a marina environment but still has many similarities w/ land ancestors. They have a streamlines body, have lost all body hair, have a tail adapted to form a fluke, have lost rear legs, have front limns adapted to become flippers, have a airway blowhole, can seal the blowhole between breaths so no water enters, can stay underwater for minutes w/ no breathing, have retained mammalian characteristics - endothermic, producing milk, advanced two-sided circulatory system, long-term parental care of their young.
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B3.2.1 - Capillaries and chemical exchange
Capillaries receive their blood from smallest arteries - arterioles. W/in body tissues arteriole branches into a capillary bed - network of capillaries that receive blood from same arteriole. Single capillary bed drains its blood into a venule (smaller vein) Blood lines up in a single file due to the lumen od each capilarru is only large enough to hold one cell at a time. Each capillary is a small tune composed of a single-cell thickness of inner tissue + a single-cell thickness of outer tissue. Both layers are very permeable. Total SA is very high. Metabolically active tissues are enriched w/ capillary beads known as highly vascular tissue. Some are more permeable so are fenestrated that allow large molecules to emit or enter. Capillaries: small inside diameter, thin walled, permeable, large SA, have fenestrations (in some)
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B3.2.2 - Arteries and veins
Arteries receive blood from the heart + takes it to a capillary bed, veins receives blood from a capillary bed + takes it back to the heart. Arteries go through high pressure so are lines w/ a thick layer of smooth muscle + elastic fibres. The lumen is smaller than veins.
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B3.2.3 - Adaptions of arteries
Arteries transport high pressure blood away from the heart. When the heart contracts a surge of blood enters an artery + its branches. Artery has a thick layer of smooth muscles controlled by the autonomic nervous system which controls those functions in the body that are not conscious. Each wall contains proteins elastin + collagen. The muscular + elastic tissues permit arteries to withstand high pressure of each blood surge. When blood is pumped into an artery, the elastin + collagen fibres are stretched + allow the blood vessel to accommodate the increased pressure. They then recoil propelling blood forwards w/ in the artery. So the arteries maintain a high pressure between pump cycles of the heart.
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B3.2.4 - Measuring pulse rate
Pulse rate is a measurement of the number of times your heart beats a minute. The carotid artery + radial artery can be touched to feel pulse rate.
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B3.2.5 - Adaptions of veins
Blood loses a lot of pressure + velocity in capillary beds so veins have thin walls + thin diameter. the unidirectional flow of slow-moving blood is aided by internal valves that prevent back glow of blood. Veins are easily compressed by surrounding muscles - activity is needed for this.
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B3.2.6
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B3.2.7 - Water transport from roots to leaves
Plant relies on transpiration to bring water + dissolved merls up from roots. Water is located in the air spaces created by the spongy mesophyll layer of the leaf. Loss of water by transpiration caused water to be pulled through the cell wall of nearby xylem tissue by capillary action/ This creates tension at the upper end of each xylem tube. This result sin movement of water up the xylem + entire column moves up due to cohesion. Upwards movement of water w/ dissolved minerals = cohesion-tension theory.
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B3.2.8 - Adaptions of xylem vessels
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B3.2.9
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B3.2.10
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B3.2.11
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B3.2.12
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B3.2.13
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B3.2.14
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B3.2.15 - The mammalian heart
right side of the heart sends blood to + from the lung capillaries in a route - pulmonary circulation. The left side of the heart sends blood to + from tissues called systemic circulation. Advantage = both lung + blood capillaries can receive blood from arteries + arterioles. this allows pressure filtration to occur in all capillaries. Cardiac muscle - highly vascular tissue making up the heart muscle, pacemaker - sinoatrial node is an area of specialized cells in the right atrium generating electrical impulses to start each heartbeat. Atria - thin muscular chambers that receive low pressure blood from capillaries of the lungs. Sends blood to the ventricles. Ventricles - thick chambers that pump blood under pressure to lungs/body. Atrioventricular valves - located between the atria + ventricles that close each heart cycle to prevent any back flow of blood to atria. Semilunar valves - close after surge of blood into pulmonary artery to prevent back flow into ventricles. Septum - wall of tissue separating right and left of the heart. Coronary vessels - provide oxygenated blood to heart.
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B3.2.16 - The cardiac cycle
Cardiac cycle leads to one heartbeat. A systole is when the chamber of the heart contracts causing an increase in pressure on the blood w/ in the chamber + blood leaves the chamber through any opening. The diastole is when a chamber is not undergoing a systole the cardiac muscle relaxes. The SA node is a croup of cardiac cells in the right atrium. It provides an electrical stimulation to regulate the contractions. If the myogenic (resting) is 72 beats per minute, the SA node is generating impulses every 0.8 seconds. Action potentials from SA node spread out almost instantly + results in the atria undergoing systole. the SA node potential reaches the atrioventricular node located in the right atrium in the septum between the right + left atria. An electrocardiogram is a graph w/ electrical activity from the SA + AV.
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B3.2.17
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B3.2.18
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B3.1.1 - The exchange of gases between organisms and their environment
As organisms increase in size it becomes more difficult to exchange oxygen + CO2 through the plasma membrane . With the surface area-to-volume ratios decreasing w/ increasing size, the distance from the centre of an organism to its exterior increases. These organisms have evolved adaptions to exchange respiratory gases. The volume of an organism shows its metabolic need to exchange respiratory gases.
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B3.1.2 - Gas exchange surfaces
Gas exchange surfaces characterized by: being thin, moist, large SA, permeable to respiratory gases. A salamander has six gills for gas exchange.
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B3.1.3 - Concentration gradients at exchange surfaces in animals
As oxygen + CO2 are exchanged by diffusion, concentration gradients must be maintained for oxygen to diffuse into the blood + CO2 out. When blood is circulated to the gills, it has recently been w/ in capillaries of tissues. Body cells are constantly respiring, utilizing oxygen then producing CO2. The blood that leaves body tissues contains a higher concentration of CO2 + lower oxygen compared to levels before the blood reached the tissues. The blood is then transported to the gill tissue + exchanges occur again. Diffusion gradients explain the gas diffusion taking place in animals w/ lungs. @ events occur to keep concentration gradients in place - water must be continuously passed over gills or refreshed in lungs, must be continuous blood flow to dense network of blood vessels in body + gills/lungs.
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B3.1.4 - Gas exchange in mammalian lungs
Lungs are subdivided into alveoli. Each alveolus is at a terminal end of 1 branch of tubes that started as the trachea. W/ each breath, most air is replaced in the alveoli. Inner surface of alveoli is lined w/ a surfactant which coats it + reduces surface tension of the moist inner surface so prevents the collapse of alveolus. Bronchioles connect into trachea for access to air. Capillaries diffuse gases surrounding the alveoli. Air inspired to the alveoli has a higher concentration of oxygen + lower concentration of CO2 compared to blood in nearby capillary. 2 types of gas diffuse according to their concentration gradient. Capillaries are 1 cell thick + each alveolus is one cell thick so it's easy for respiratory gases to move in and out. The oxygen rich blood then returns to the heart to be pumped out into respiring tissues. This occurs as long as the heart continues to send blood to capillaries in the lungs + air is refreshed in alveoli.
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B3.1.5 - Lung ventilation
Boyle's law states that an increase in volume will lead to a decrease in pressure. Lungs are located in the thoracic cavity which is closed to outside air. Inside, there is 1 opening through the trachea. Diaphragm is large, dome-shaped muscle that is the bottom of the cavity. When it contracts it flattens the dome shape + increases the volume of the cavity. 1. When inspiring the diaphragm contracts, increasing volume in the cavity. 2. the external intercostal muscles + 1 set of abdominal muscle both contract to raise the ribcage which increase the volume in then cavity. 3. The cavity has increased in volume so the pressure decreased leading to less pressure on tissue. 4. Lung tissue responds to low pressure by increasing its volume. 5. Partial vacuum caused by decrease in pressure. Air comes in through trachea to counter the partial vacuum + fills the alveoli. When exercising everything is exaggerated.
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B3.1.6 - Lung volume
Spirometer measures lung volume. Tidal volume - air breathed in/out during cycle at rest. Inspiratory reserve volume - max. volume of air a person can breathe in. Expiratory reserve volume - max. volume of air a person can breathe out. Vital capacity - sum of inspiratory reserve volume, tidal + expiratory reserve volume.
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B3.1.7 - Gas exchange in leaves
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B3.1.8 - Leaf tissue distribution
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B3.1.9 - Transpiration
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B3.1.10 - Stomata
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B3.1.11 - Haemoglobin and oxygen transport
Haemoglobin carries most oxygen w/ in bloodstream. Erythrocytes have no nuclei + few organelles. Each molecule can reversibly bind to oxygen + CO2 molecules. Heamoglobin has a quaternary structure w/ 4 polypeptides each having a harm group near its centre. When haemoglobin reversibly binds to an oxygen. the iron atom w/ in the ham group bonds w/ the oxygen. Haemoglobin can transport oxygen molecules due to this. When in that form the haemoglobin is said to be saturated. An oxygen molecule bonded to haemoglobin increases its affinity for more oxygen. This is called cooperative binding. 3 oxygen molecules carried has the most affinity, but no oxygen molecules carried is the least affinity. Binding of CO2 to the polypeptide chains of haemoglobin + resulting change in haemoglobin affinity for oxygen is called allostery. In this, CO2 binds to the polypeptide regions of the molecule. Each area where CO2 binds in the allosteric site. Binding of CO2 to haemoglobin results in an increase in the release of oxygen molecules known as a Bohr shift. In the placenta, her capillaries come close to the ones of the foetus allowing molecular exchanges between the mother + the foetus including oxygen and CO2 allowing molecular exchange between them. The foetus doe snot breathe but is carrying out cell respiration + blood sent to foetal side is low in oxygen + high in CO2. The concentration gradient between the blood of mother + foetus aided by the foetal haemoglobin's greater affinity for oxygen encouraging diffusion of the mother's oxygen to the foetus.
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B3.1.12 - The Bohr shift
When haemoglobin bonds to a CO2 molecule, its affinity for oxygen decreases. AKA haemoglobin has a greater tendency to give up oxygen molecules in the presence of CO2. This change in affinity is called the Bohr shift. There are benefits of this for actively respiring tissues as the haemoglobin as a renewed affinity for bonding to oxygen (I think)
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B3.1.13 - Oxygen dissociation curves
Oxygen dissociation curve = S-shaped curve formed from cooperative binding. X-axis shows the partial pressure of oxygen. The y-axis shows % of haemoglobin saturation (haemoglobin that is transporting the max. of four oxygen molecules) There is enhanced affinity of foetal haemoglobin over maternal which is seen by comparing their oxygen dissociation curves. The foetal curve is shifted the left of the mothers indicating a greater affinity for oxygen at almost every partial pressure of oxygen. the Bohr shift, causes a shift to the right. The Bohr shift serves as an advantage when exercising as our muscles need more oxygen for cellular respiration + increased rate of cell respirations leads to more CO2 production binding to haemoglobin in capillaries. This leads to increased release of oxygen to the muscles where it's needed.
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B2.3.1 - Cell reproduction an organism development
Zygote forms from fertilization - two gamete cells fuse. Morphogens = signal molecules controlling differentiation. these occur is gradients in regions of the early embryo. The concentration of signal molecules controls the regional development of the first cells into head + tail structures. The gradient of the signalling molecules results in diff. genes being expressed in diff. parts of the embryo developing diff. features.
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B2.3.2 - Stem ells
Stem cells are able to divide indefinitely + can differentiate along diff. pathways - all cell types an organism possesses. Plants contain meristematic tissue which rapidly reproducing cells that can become various types of tissue w/ in the root or stem.
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B2.3.3 - Stem cell niches
Stem cells can 1. self-renew meaning both daughter cells may remain as stem cells of a stem cell / a differentiated may be formed but either way stem cells are maintained. 2. They can recreate functional tissues as they differentiate when cell signalling ensures specific genes are expressed as the cell develops. Stem cell niches are stem cells present in high numbers has a result of regular proliferation.
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B2.3.4 - Types of stem cell
Table on 256. Scientists saw possibilities of using stem cells to treat disease but stem cells cannot be distinguished by their appearance.
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B2.3.5 - Cell size and specialization
Cell size varies widely across. Table on 257. Striated muscle fibres are found in skeletal muscle. Produces a significant movement.
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B2.3.6 - Constraints on cell size
The SA-to-Volume ratio limits a the size a cell can reach.
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B2.3.7 - Surface area-to-volume adaptions
Cells larger in size have modifications allowing them to function efficiently. - changes cell shape, cellular projections, location relative to sources of nutrients, how cells fit together. Cells that line the part of human kidney - proximal convoluted tubule have several adaptions that increase their ability to reabsorb fluids + secrete ions. The disc shape of red blood cells allow a greater surface area-to-volume ratio.
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B2.3.8 - Lung alveoli
Type 1 pneumocytes cover 95% of the alveolar surface - allow gas exchange between alveoli + capillaries. Adaptions - thin + flat to increase SA + minimize diffusion distance. Shared basement membrane minimizing diffusion distances for respiratory gases. Tightly joined to each other so fluids cannot enter the alveoli from the capillaries. type 2 pneumocytes - make up less than 5% of the surface. they produce the pulmonary surfactant reducing surface tension + preventing alveoli from collapsing. Adaptions - cube shape for more area. Microvilli oriented towards alveolar sac increasing SA + allowing more surfactant secretion. Cytoplasm containing organelles involved w/ surfactant production + secretion. Ability to transform into type 1 when needed.
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B2.3.9 - Muscle fibres
Cardiac muscle fibres occur in the heart + have banded cells like striated skeletal muscle cells but w/ adaptions such as being composed of branching striated cells, having single nucleus per fibre/cell, being connected at ends by intercalated discs. It Is debated whether striated skeletal muscle fibres should be considered cells for multiples reasons but they still have many organelles that cells do.
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B2.3.10 - Sperm and egg cells
Table on 264.
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B2.2.1 - Cell compartmentalization
Cell compartmentalization allows the cell to work more efficiently. Studying each part of the cell individually is called reductionism. To study this we use biochemical fractionation (separation of specific chemicals/structures) Chromatography. Cell fractionation (extraction of organelles from cells - cells mixed in a tube that breaks down cell membranes - sample is spun at a high speed to isolate components) Gel electrophoresis (separates molecules from diff. types by passing them through gel using an electrical charge. Table of organelles on 241.
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B2.2.2 - The nucleus and cytoplasm
Transcription + translation produce proteins. Compartmentalization allows this greater cell efficiency of having isolation between these two processes.
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B2.2.3 - Compartmentalization of the cytoplasm
Lysosomes participate in breakdown of wastes requiring potentially destructive enzymes that may cause damage to the cell if not isolated. When endocytosis occurs, a phagocytic vacuole often is produced. This vacuole protects the contents from damage when phagocytosis occurs. this vacuole moves around the cell till it contacts a lysosome then fuses allowing inactivation of the threat. Challenges w/ compartmentalization = cell must develop means of integrating all separate functions.
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B2.2.4 - The mitochondrion
Mitochondria are adapted to produce ATP. Table on 244.
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B2.2.5 - the chloroplast
Respiration is a catabolic process while photosynthesis is an anabolic process. Table on 246.
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B2.2.6 - The double membrane of the nucleus
Double membrane = nuclear envelope + provides an area where DNA can carry out its functions w/ out interruption. Nuclear pores allow diffusion between nuclear material, nucleoplasm + cytoplasm.
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B2.2.7 - The ribosome
Ribosomal RNA are two subunits that make up each ribosome. All ribosomes produce proteins.
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B2.2.8 - The Golgi apparatus
Golgi apparatus consists of flattened sacs that engage in producing + secreting substances. One side of the stack of flattened sacs is located near the ER (cis side) The other is towards the plasma membrane (trans side) Protein filled transport vesicles are received on the cis side from either ER.
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B2.2.9 - Cellular vesicles
Clathrins are proteins in the cell membrane that anchor proteins to specific sites. It proteins line coated pits, allowing the receptors to bind to specific molecules.
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B2.1 - membranes
Complete all 17
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B1.2.1 - The common structure of amino acids
There are 20 diff. amino acids. Must be able to draw the structure that is common to all amino acids. The letter "R" is used to represent what is unique to each of the 20. Drawing is on 199.
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B1.2.2 - Condensation reactions bond amino acids together
Equation for condensation reaction forming a covalent bond between 2 amino acids is: amino acid 1 + amino acid 2 => dipeptide + water. The new covalent bonds linking the amino acids tog. = peptide bonds.
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B1.2.3 - Essential amino acids
our cells can synthesize 11 of the 20 amino acids from other amino acids. Nine come from our diet so we must eat these essential amino acids as they cannot be synthesized - must come from food. Non-essential amino acids cane made from other amino acids. Vegan diets require attention to ensure essential amino acids are consumed.
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B1.2.4 - The vast variety of polypeptides
Huge variety of polypeptides is possible because: DNA codes for the number + order of amino acids w/ in polypeptides, 20 diff. amino acids. Polypeptides can very in length, from a few to thousands of amino acids. Some polypeptides are modified by cells after initial synthesis. Amino acids can be arranged in any order. Some common polypeptides include - haemoglobin, keratin, lipase, collagen, histones, and insulin.
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B1.2.5 - The effect of pH and temperature
Proteins folded to form globular proteins. At high temperature intramolecular bonds are susceptible to alterations. The hydrogen bonds cannot stay intact under this stress resulting in loss of shape or function - called denaturation. The protein may return to its norms shape if returned to optimal temp. This occurs with a non optimum pH
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B1.2.6 - R-groups provide diversity
There are 20 R-groups so 20 amino acids. r-groups determiner the properties of assembled polypeptides. r-groups are hydrophilic (polar, acidic/base) or hydrophobic. Table on 205.
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B1.2.7 - Primary structures of a protein
Number + sequence of amino acids held tog. by peptide bonds = primary structure of the protein. The sequence is determined by a gene. Each gene codes for the synthesis of the same protein many times till not needed. Proteins are precise, predictable + repeatable because each tine DNA in the gene will be translated into the same sequence of amino acids: primary structure.
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B1.2.8 - Secondary structure of a protein
2 possible shapes that can result when the primary stricture of a protein contains only non-polar R-groups. A possibility is beta-pleated sheet + other is alpha helix. These shapes are held tog. by hydrogen bonds which are in regular positions. Proteins are fibrous when they are made up of non-polar amino acids creating insoluble molecules. Actin + myosin are fibrous.
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B1.2.9 - Tertiary structure of a protein
Bonding interaction that can occur between amino acids at tertiary level: 1. Ionized R-groups align w/ each other to form an ionic bond. 2. Non-polar amino acids, being hydrophobic fold into an area w/ in interior of the polypeptide to avoid polar water. - hydrophobic interaction. 3. Pairs of cysteine amino acids form a covalent bond between themselves + the polypeptide. Results in a disulphide bond - strongest of all bonding forces. (More maybe on this) 4. Polar amino acids will form H bonds w. each other often found on or near exterior of polypeptide due to hydrophilic properties.
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B1.2.10 - Polar and non-polar amino acids
Proteins composed of non-polar amino acids = poor solubility in cytoplasm. Lipase is an enzyme which catalyses hydrolysis of lipid molecules. Lipids have long hydrocarbon tail regions which only interact w/ an enzyme that is non polar. Lipase folds into its three-dimensional shape. The primary structure allows high concentration of hydrophobic amino acids o fold into the inside or core of the enzyme + high concentration of hydrophilic amino acids on the outside of the molecule. the outer polar amino acids permit solubility in a water environment. Glycoproteins called A and B determine ABO blood type. The protein portion must fold so that non-polar amino acids can interact w/ the hydrophobic layers of the membrane to remain embedded / Folding leads t polar amino acids bonding to the sugar component. As well, folding leads to polar amino acids bonding to sugar component of the molecule + interacting w/ the aqueous blood plasma.
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B1.2.11 - Quaternary structure of proteins
Quaternary structure = 2 or more amino acid chains bonded tog. to form a single molecular structure. Insulin is first synthesized by pancreatic cells in a chain of 110 amino acids. Then this is modified when pancreas cells become 2 chains. 1 is 21 amino acids long other is 30. These join tog. which include 4 disulphide bonds w/ in the 51 amino acid structure. Insulin is inactive while in the pancreas as it forms timers, 2 insulin molecules temporarily bonded. 3 dimers can bond to form a hexamer. Collagen's a fibrous protein that consists of 3 polypeptide chains wound around into a helix shape. this is a quaternary structure. Haemoglobin binds reversibly to oxygen in the lungs + carry oxygen to body tissues where it is released for aerobic cell respiration. It can also bind reversible to CO2 to be taken to lungs + exhaled. Haemoglobin = quaternary structured protein. It also exhibits each type of protein structure. Haemoglobin has 2 diff. primary strictures. A secondary structure is seen in alpha helix structures w/ in portions of each polypeptide. Tertiary structure is shown by each of the four globular polypeptides. A quaternary structure is shown by the bonding of the 4 polypeptides into a single haemoglobin molecule. Haemoglobin is conjugated - 1 or more on-protein groups as part of the molecule.
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B1.2.12 - Protein shape and its function
Collagen = a fibrous protein w/ an alpha helix secondary structure making up connective tissues. Amino acids w/ in collagen are short repeating sequences. The structural uniformity makes it excellent to build body tissues tog. Insulin has globular shapes which allows a peptide hormone to have a specific shape to fit a membrane protein so the hormone can act as a signalling molecule. Every antibody has a unique shape to chemically recognize an antigen. Insulin is released into the bloodstream after blood glucose levels rise. When insulin fits into the membrane receptor a set of reactions occur called a signal pathway. This results w/ the cell opening its channels in the plasma membrane that allow glucose to enter the cell.
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C1.1.1 - Enzymes as catalysts
Organic catalysts enzymes - help reaction occur faster.
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C1.1.2 - Metabolism
Metabolism - includes all chemical reactions that occur in an organism. Each is controlled by an enzyme. All chem. reactions involve reactants + products.
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C1.1.3 - Anabolism and catabolism
Complex => simpler = anabolic - anabolism. Break down complex molecules + release energy = catabolic - catabolism. Table on 364. And 365. Kilocalorie (1000 calories) - unit to measure heat. ATP - supplies energy for macromolecules, for mechanical work, for movement.
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C1.1.4 - Globular proteins and active sites
Somewhere on enzyme is an area that matches enzyme's substrate - active site. If this is changed it is denatured.
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C1.1.5 and C1.1.10 - Enzyme activation
Lock-and-key model. Lock = active site. Key = substrate. Now is known as induced-fit model - fits like a glove as it undergoes significant change to the shape as it combines w/ the active site. the changes in shape causes stress on the bonds so is now destabilized which favours reactions. Enzymes lower activation energy. - energy needed to destabilize existing bonds so a reaction can proceed. 2 ways to overcomes energy barrier + increase rate 1. Increase energy of reacting molecules - increased collisions. 2. Lowering activation energy required to stress partially bonds so it is broken easier. Graph on 368.
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C1.1.6 - Molecular motion
Movement is needed for a substrate molecule + an active site to come together. (shape also needed) Large substrate molecules may be immobilized while sometimes enzymes might be immobilized by being embedded in membranes.
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C1.1.7 - Mechanism of enzyme action
Enzyme action - surface of substrate contacts active site, enzyme + substrate change shape to fit, temp. complex called enzyme-substrate complex forms, activation energy lowered + substrate is altered, transformed substrate product is released from active site, unchanged enzyme is free to combine w/ other substrates. Shown on 370.
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C1.1.8 - Factors affecting enzyme-catalysed reactions
Temp. can increase reaction rate but if limit is reached denaturation occurs. Same w/ pH. Table on 372. Collision theory - if concentration increases in the reactant, there are more molecules to react + collide w/. There is a max. limit to thesis there is 1 active site. If every active site is occupied adding more solution will not increase the reaction.
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C1.1.9 - Measuring enzyme-catalysed reactions
Measuring rate of an enzyme-controlled reaction measures either the rate at which the substrate is used or the rate which the product is used.
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C1.1.11 - Intracellular and extracellular reactions
Intracellular enzyme (w/ in) include glycolysis taking place in the cell or Krebs cycle taking place in the matrix of the mitochondria. Extracellular (outside) include chemical digestion w/ in digestive system which is catalyzed by extracellular enzymes. Multienzyme complexes - groups of enzymes working together to catalyze reactions inside + out of the cell.
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C1.1.12 - Metabolic efficiency
Variation occurs in metabolic reactions as it is not 100% efficient. Heat generation is inevitable as metabolic reactions are not 100% efficient in energy transfer. Many organisms depend on heat production for maintenance of content body temperature. (endotherms)
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C1.1.13 - Metabolic pathways
Metabolic reactions cocue in metabolic pathways. Glycolysis is a metabolic pathway. It is apart of cellular respiration. Krebs cycle is cyclical. Calvin cycle (in photosynthesis) is cyclical.
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C1.1.14 - Non-competitive inhibition
Enzyme inhibition occurs when an inhibitor binds to an enzyme + decreases activity by altering the active site. Non-competitive inhibition (allosteric inhibition) occurs when an inhibitor interacts w/ another active site (allosteric site) on the enzyme. This causes the ions to bind to sulfer groups + results in shape changes in the enzyme.
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C1.1.15 - Competitive inhibition
Competitive inhibition is affected by substrate concentration. When people have high levels of cholesterol doctors recommend statins which is a competitive inhibitor as it combines w/ the active site of an enzyme.
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C1.1.16 - Feedback inhibition
Feedback inhibition prevents the cell from wasting resources by making more than it needs. Many metabolic reactions are linear pathways w/ an end product. When the end product result, the pathway shuts down. This is due to the end product inhibiting the action of the enzyme in the first step of the pathway. When present in high concentrations, the end product binds w/ the allosteric site of the first enzyme, bringing inhibition. As the end product is used by the cell, the enzyme is reactivated. This is an allosteric enzyme. Humans cannot synthesize the amino acid isoleucine. Plants + bacteria can so we must ingest them they synthesize it using feedback inhibition. The pathway is inactive when lots of isoleucine are present as it combines w/ the allosteric site of threonine deaminase (first enzyme in the pathway) When this happens the active site is altered + can no longer combine w. the initial substrate, threonine. If the concentration of isoleucine is low, threonine deaminase can combine w/ threonine allowing the pathway to proceed.
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C1.1.17 - Mechanism-based inhibition
Penicillin inhibits an enzyme which catalyses the last step in the formation of bacterial cell walls - irreversibly binds to it + inactivates it. Some strains of bacteria are resistant now to penicillin due to mutation that produces an enzyme, penicillinase.Scientists have changed their make-up of penicillin to produce variants that are not inactivated by this, Another is transpeptidases which are enzymes which function in the formation of bacteria cell walls. Penicillin inhibits these enzymes so there is inhibition of bacteria cell walls.
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C2.1.13 - Effects of estradiol and progesterone on target cells
Oestradiol and progesterone directly affect gene expression as they affect transcription. The hypothalamus influences heart beat, blood pressure, appetite, body temp. and water balance. As well controls secretions of the pituitary gland. Oestradiol influences the hypothalamus in secretion of gonadotropin-releasing hormone. this stimulates release of gonadotropic hormones stimulating ovaries to produce eggs. Progesterone prepares the wall of the uterus for pregnancy.
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C2.1.14 - Regulation of cell signalling pathways
Homeostasis - the regulation of an organisms internal environment. Positive and negative feedback systems occur to allow adjustments in the environment to the organisms. Negative feedback: regulation of blood glucose. - 2 hormones insulin + glucagon are involved. These are produced in the pancreas by islet cells. Beta islet - secrets insulin. Alpha islet - secretes glucagon. These 2 act in opposite ways to control blood glucose levels. Shown on 445. Positive feedback: fever. During a fever, the pathogen enters the body + is detected causing body temp. to increase, the positive feedback causes a large deviation from normal, the fever peaks + body temp. begins to fall. Positive feedback systems reinforce or amplify a response.
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C1.2.1 - ATP structure and function
Adenosine triphosphate is a nucleotide. Enzymes catalyse a series of reactions where covalent bonds break (oxidized) Phosphate groups are negatively charged so they repel one another - unstable covalent bond between the two - high-energy bond. these bonds have low activation energy + easily broken through hydrolysis. This reaction is exergonic - energy releases. This energy is used for cellular work.
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C1.2.2 - Life processes within cells require ATP
Cellular work carried out using energy released from ATP includes active transport, synthesis of macromolecules by anabolism, movement of the whole cell by cilia or flagellum action, movement within the cell of cell components - mitosis/meiosis.
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C1.2.3 - ATP and ADP
ADP to ATP is an endergonic reaction. When ATP undergoes hydrolysis to form ADP plus is a separated phosphate group, energy is released causing an exergonic reaction.
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C1.2.4 and C1.2.5 - ATP and cellular respiration
Glucose and fatty acids are the principal substrates for cell respiration but a wide range of carbon/organic compounds can be used. Initial stage of anaerobic cellular respiration is glycolysis. Fermentation: alcoholic fermentation and lactic acid fermentation. The final stage is electron transport chain - occurs in Cristal of mitochondria.
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C1.2.6 - The rate of cell respiration
Factors that affect the overall rate of cell respiration include: temperature (optimal is 20-30 degrees celsius), CO2 concentration, Oxygen concentration, glucose concentration, the type of cell. Respirometers are used to calculate the rate of cell respiration.
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C4.1.1 - Populations
Population - group of individuals of the same species in the same geographical area able to interbreed. Emperor penguins - more than one pop. due to ability to interbreed. Reproductive isolation is used to distinguish 1 population of a species from another.
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C4.1.2 - Estimating population size
We rely on estimates for population size. We use systematic - utilizing a line/grid + counting at regular intervals. Random sampling - arbitrarily chosen zones are sampled. This overcomes bias. - utilizes quadrants + method of mark + recapture.
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C4.1.3 - Sampling sessile organisms
Random sampling can be used to organisms that are sessile (stay in one place) A quadrate is used - a square of a dimension. Using this means the SA of the sample is the same for each count that is taken.
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C4.1.4 - Sampling motile organisms
Capture-mark-release-recapture method enables estimates of the number of animals in an ecosystem. It is used in place of quadrants for motile organisms. Some of a population is marked then released to remix w/ their population. A second sample is then captured - some will be marked some are unmarked. The proportion in the second sample is assumed to the the same as the individuals in the first sample to the whole population. The Lincoln index is then used. Total pop. = # of individuals caught + marked initially x number of all individuals recaptured/ # of marked individuals recaptured. (Total pop. = M x N/R) Limitations to this include injuries, visibility to predators, assumes the population is closed.
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C4.1.5 - Carrying capacity
Carrying capacity - limit the habitat can support (K) Trees as an ex. cannot all catch all sunlight, new trees will have trouble getting it. A limiting factor is something that prevents a population from getting bigger. - Availability of resources, build-up of waste, predation, disease.
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C4.1.6 - Negative feedback
Density-dependent factors = factors that change the size of a population dependent on the density of the population (disease) Density-independent = does not matter is there is little or large pop. In positive feedback loops, more offspring grows up + produces more and on. Negative feedback loop could be disease causing the population to slow down.
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C4.1.7 - Population growth
Tree species on Mount saint Helens, have increased, while some have decreased. Sigmoid growth curve includes the exponential phase - fast rate of growth. Transitional phase - growth rate slows. Plateau phase - no more growth.
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C4.1.9 - Communities
A community - group of populations interacting w/ each other in an area.
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C4.1.10 - Intraspecific relationships
Intraspecific relationships = interactions between the same species. This can include competition / cooperation. Intraspecific cooperation - individual helps another from the same species. (wolves) Intraspecific competition - members of same species compete for resources.
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C4.1.11 - Interspcific relationships
Interactions between different species in a community = interspecific relationships. Table on 533.
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C4.1.12 - Mutualism
Mutualism - type of interspecific cooperation benefiting both species. Ability to turn gaseous nitrogen to usable nitrogen = nitrogen fixation. Rhizobium can do this - lives in root nodules of legume family plants. - Converts nitrogen into ammonia which acts as a fertilizer. Bacteria having this relationship = symbiotic. The bacteria Rhizobium receives carbs from the root in return. Mycorrhiza occurs when a plant + fungus help each other. Coral reefs are built up of coral polyps. In their tentacles are photosynthetic algae - zooxanthellae. These coexist as a symbiotic relationship w/ coral polyps giving them goof in form of carbon based energy. Coral polyps gives zooxanthellae CO2 and minerals for photosynthesis + growth. Coral bleaching occurs when zooxanthellae leaves/dies. The CaCO3 does not have any pigment so shows white.
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C4.1.13 - Endemic and invasive species
Endemic - no where else in the world. Invasive species are introduced into a new area from a distant origin + their populations grow well so they cause problems for species already living there. An example is the tortoise's who were endemic to Galápagos Islands which died off as there were competitions w/ goats. Human brought these goats over.
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C4.1.14 - Interspecific competition
Presence-absence matrix is indicated if one species is more successful in the absence than another. The uses of experiments were labs, field observations by random sampling, and field manipulation.
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C4.1.15 - The chi-squared test
The chi-squared test of association sees whether 2 species tend to occur together more often than they would by chance or if they are never found coexisting.
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C4.1.16 - Predator-prey relationships
Predator prey relationship - As the lynx offspring grows, the population increases to its max. But by the time the 2 lines cross, the hare population has declined rapidly due to the lynxes hunting too many of the hares. After the lynx reaches its max. the hare population reaches its minimum. At this time we see the predator line going down as the lynx population decreases dye to lack of food. This is a density-dependent relationship.
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C4.1.17 - Control of populations
Top-down controls are seen when a species population can be reduced by other species feeding on it. Herbivory is top-down. Bottom-up controls are seen when a species population can be reduced by lack of resources. Both of these influence ecosystems but one is usually dominant. Marine- bottom-up dominant.
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C4.1.18 - allelopathy and antibiotic secretion
Primary metabolites - molecules needed for basic function of life. Secondary metabolites kill primary metabolites. The secondary are used in allopathy - production of metabolites that influence the growth + success of other organisms. (inhibiting seed germination, interfering w/ nutrient uptake, killing bacteria) In Garlic mustard - a secondary metabolite, sinigrin can inhibit germination of seeds from other plants + can reduce growth of roots growing. Peniccilium Rubens produces a molecule to stop growth of bacteria.
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C4.2.1 - Ecosystems are open systems
Open system = allows matter in and out. Closed system = no matter leaves so it must be recycles. Systems theory provides an explanation of how systems interact w/ each other.
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C4.2.2 - Sunlight sustains most ecosystems
In deep ocean water in caves or deep underground it is difficult to access sunlight or hydrothermal vents. These use dissolved sea water warmed by magma which rises to the surface + provides a Ruch source of minerals for chem. reactions. Photosynthetic organisms take inorganic CO2 and convert it to sugar.
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C4.2.3 - The flow of energy
chemical energy passes to a consumer as it feeds on an organism that is the previous stage in a food chain. Process of energy passing through feeding is flow of energy through a food chain.
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C4.2.4 - Food chains and food webs
Arrows in food chains and webs indicate direction of transfer of energy + biomass. Food chain - single linear set of connections. Web - multiple food chains.
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C4.2.5 - Decomposers
Decomposers break down non-living food sources such as faeces, entire dead bodies, or fallen leaves/skin of snake. Saprotrophs secrete enzymes onto dead matter + absorb the nutrients. Detritivores ingest dead matter + digest it inside their bodies. The digestive enzymes decomposers convert the organic matter to a usable form. They recycle nutrients so it is available for others.
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C4.2.6 - Autotrophs
Autotrophs make their own food through organic molecules. They synthesize their organic molecules from simple inorganic substances - photosynthesis or chemosynthesis. Photoautotrophs take light energy + combine it w/ inorganic substances to obtain a source of she,. energy in the form of a carbon compound.This ability to convert inorganic CO2 into organic molecules useful for energy = carbon fixation. Once this is done, molecules are combined using anabolic reactions to make larger molecules. Chemoautotrophs make CO2 using inorganic compounds as energy to build more complex molecules for food. Examples of photoautotrophs: clover, algae. Chemoautotrophs: iron, surfer and nitrogen oxidizing bacteria.
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C4.2.7 - Energy sources
Oxidation reactions release energy so they are useful in living organisms. Electrons are removed from atoms + donated electrons are free to participate in reaction in the cell. Light is used by photosynthetic organisms to oxidize water molecules which releases oxygen gas. The ATP produced using the donated electrons + hydrogen ions can be used to generate the organic molecule glucose w/ CO2 as source of carbon. Iron-oxidizng bacteria - Mariprofundus ferrooxydans thrives in hydrothermal vents. They obtain electrons from iron by taking one form of iron (II) + removing an electron to turn into iron (III). This oxidation reaction is used to generate ATP for the cell.
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C4.2.8 - Heterotrophs
Heterotrophs obtain organic molecules from other organisms. They get their chem. energy from autotrophs/heterotrophs. Heterotrophs digest proteins into amino acids, lipids into fatty acids + DNA / RNA into nucleic acids. They can synthesize their own proteins using the amino acids, make their own lipids using fatty acids, + synthesis their own dNA + RNA using nucleic acids. Process of integrating nutrients to usable substances = assimilation.
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C4.2.9 - The release of energy by cell respiration
To release energy, carbon compounds such as glucose are oxidized. Cells need a constant supply of energy - cellular respiration.
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C4.2.10 - Trophic levels
Trophic level = amount of organisms the energy in the system has flown through. Primary consumer => secondary consumer => tertiary consumer.
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C4.2.11 - Energy pyramids
A pyramid of energy is used to show how much + how fast energy flows from one trophic level to the next. unit = kilojoules.
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C4.2.12 - Energy loss between trophic levels
Organisms use 10-20% of the energy available used from the previous step. This is due to - organism not swallowing some parts, not all food swallowed is absorbed, some organisms die w/ out having been eaten, considerable heat loss due to cellular respiration.
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C4.2.13 - Heat loss from cell respiration
Energy transfers are not 100% efficient so heat is produced both when ATP is produced in cell respiration + when it is used in cells.
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C4.2.14 - The number of trophic levels
Most food chains have four trophic levels (max. 6) The biomass of a trophic level is an estimate of the mass of all organisms in that level. At each successive stage in food chains, there are fewer organisms or smaller organisms - less biomass but energy content is not reduced.
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C4.2.15 - Primary production
Cooler biomes have a lower biomass - cannot support many organisms. Biomes tend to occupy zones that cover wide expanses. Primary production - biomass generated by activity of producers such as photosynthetic organisms when they fix carbon + make carbon compounds as a food source. Biomass accumulate when autotrophs + heterotrophs grow.
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C4.2.16 - Secondary production
Conversion of one form of carbon to another inside consumers = secondary production. Due to loss of biomass when carbon compounds are converted to CO2 + H2O in cell respiration, secondary production is lower than primary production in an ecosystem.
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C4.2.17 - The carbon cycle
Carbon is found in the biosphere, atmosphere, lithosphere. It is constantly cycled between living organisms + inorganic processes that make carbon available. When cellular respiration is complete, CO2 is released so when an animal dies, its body will be eaten + remains are broken down by decomposers. CO2 is absorbed by photoautotrophs. Methane -?).
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C4.2.18 - Carbon sinks and sources
A carbons source in an ecosystem = net producer of CO2. Carbon sink = organism that absorbs + holds more carbon than it releases. If photosynthesis exceeds respiration there is a net uptake of CO2 + if respiration exceeds photosynthesis there is a net release of CO2.
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C4.2.19 - The release of carbon dioxide during combustion
Carbons inks vary in date formation + combustion following lighting strikes sometimes happens naturally but humans have greatly increased this.
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C4.2.20 - The Keeling Curve
Longest continuous monitoring of CO2 concentration was carried out by National Oceanic + Atmospheric Administration. This was chosen due to highly industrialized zones. Graph on 566.
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C4.2.21 - The dependence on atmospheric oxygen and carbons dioxide
CO2 + H2O => glucose + oxygen. - Photosynthesis. Aerobic cellular respiration: glucose + oxygen => CO2 + H2O. opposites of each other.
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C4.2.22 - The recycling of chemical elements
Many other elements other than carbon are cycled too. Nitrogen, hydrogen, oxygen, calcium, potassium, sodium, iron, phosphorus etc.
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D3.2.1 - Haploid games and diploid zygotes
Diploid = nucleus which has chromosomes organized into pairs of homologous chromosomes. Gametes are haploid. Variable n = 23 chromosomes. A zygote forms from 2 haploid nuclei forming together.
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D3.2.2 - Genetic crosses in flowering plants
Mendel took purebred tall plants + crossed them w/ purebred short plants. Pollen contains male gametes + female gametes are located in the ovary, so pollination is needed to carry out a cross. Plants such as peas produce both male + female gametes on the same plant, allowing self-pollination - self-fertilization. Genetic crosses are widely used to breed new varieties of crop.
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D3.2.3 - Combination of alleles
Homozygous - identical alleles. Heterozygous - 2 different alleles.
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D3.2.4 - Phenotype
Phenotype = observable characteristics of an organism. Such as ABO blood type, Huntington's disease. Phenotypes by the environment include learned behaviour + acquired physical traits.
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D3.2.5 - Dominant and recessive alleles
Dominant allele - allele that has the same effect on the phenotype whether it's paired w/ the same allele or a different one. A recessive allele has an effect on the phenotype only when no dominant allele is present. A codominant allele are pairs of alleles that both affect the phenotype in a heterozygote. Both a homozygous-dominant genotype and a heterozygous genotype for a particular trait will produce the same phenotype.
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D3.2.6 - Phenotypic plasticity
Phenotypic plasticity = organisms ability to express its phenotype differently depending on the environment. It could be reversible during the lifetime of an individual.
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D3.2.7 - Recessive genetic conditions
Phenylketonuria is a recessive genetic condition caused by mutation in an autosomal gene which does for the enzyme to convert phenylanine to tyrosine.
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D3.2.8 - Single-nucleotide polymorphisms and multiple alleles
Any number of alleles of a gene can exist in the gene pool but an individual only inherits two. SNPs occur when a nucleotide of a genetic code is not found where expected.
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D3.2.9 - ABO blood groups
I^A = alelle for producing proteins called type A antigens. I = the recessive allele that produces neither A nor B antigens.
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D3.2.10 - Intermediate and dual phenotypes
AB blood type shows incomplete dominance in its flower pigmentation. This is an example of heterozygotes having a dual phenotype. In incomplete dominance, heterozygotes have an intermediate phenotype. An example of this is the four o'clock flower CW.
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D3.2.11 - Sex determination
Sex chromosomes in sperm determines whether a zygote develops certain male-typical or female-typical physical characteristics + more genes are carried by the X chromosome.
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D3.2.12 - Haemophilia
Any gene locus on the X or Y chromosome is sex-linked. A genetic trait is haemophilia. Alleles carried on X chromosomes as superscript letters on an uppercase X.
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D3.2.13 - Pedigree charts
Pedigree - organisms ancestry.
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D3.2.14 - Continupus variation
Polygenic inheritance involves two or more genes influencing the expression of one trait. Array of possibilities = continuous variation. Discontinuous is distinct categories.
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D3.2.15 - Box-and-whisker plots
Box-and-whisker plot uses quartiles. The median = value in data set to max or min. Quartile 1 is the middle value between the median + lowest value in data set or 25th percentile. Quartile 2 is the median at the 50th percentile. Quartile 3 is the middle between the median + the highest value - 75th percentile. The IQR measures the spread of data between the 75th and the 25th.
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D3.2.16 - Segregation and independent assortment
The movement of chromosomes in meiosis and the outcome of dihybrid crosses involving pairs of unlinked genes. The law of segregation says each game will receive only one of the two copies that the parents can give. The 9:3:3:1 is due to movement of chromosomes during meiosis. Mendels' law of independent assortment - each gene is passed on independently of other genes.
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D3.2.17 - Predicting genotypic and phenotypic ratios
The FOIL method is used. 9:3:3:1 or 1:1:1:1
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D3.2.18 - Gene loci and polypeptide products
AOS.
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D3.2.19 - Gene linkage
Linked genes are passed on to the next generation together. A linkage group is a group of genes inherited together because they are on the same chromosome. Symbols used to denote alleles are shown alongside vertical lines representing homologous chromosomes.
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D3.2.20 - Recombinants
Recombinant = used to describe both new chromosome + resulting organism.
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D3.2.21 - Chi-squared tests
p = 0.05, null/ alternative hypothesis.
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D3.1.1 - Sexual and asexual reproduction
Sexual reproduction requires both female and male parents, each contributing some of their genes to their offspring. Asexual reproduction requires only one parent + results in many identical organisms. Asexual reproduction includes : binary fission, mitosis, budding, fragmentation, vegetative reproduction, parthenogenesis.
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D3.1.2 - The role of meiosis and gametes
Reduction division = meiosis. Each homologous pair has a maternal + paternal chromosome. Fusion (fertilization) of games produces new combinations.
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D3.1.3 - Male and female gametes
Sperm are motile + have a flagellum. A sperm contributes nothing towards the food reserves for the early embryo. Sperms are very small compared to eggs. An egg provides all nutrients for the embryo. There are millions of sperm which try to reach the single egg.
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D3.1.4 - Male and female reproductive systems
Table + view on 690.
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D3.2.5 - Hormonal control of the menstrual cycle
The menstrual cycle lasts 28 days and it is designed to release an egg (ovulation) + later implantation into inner lining of the uterus. This implantation occurs when the uterine inner lining (endometrium) is rich w/ blood vessels. The hypothalamus produces the GnRH which targets the pituitary gland which then produces FSH + LH which target the ovaries. These have multiple effects: increases secretions of oestradiol which targets the endometrium + increases the density of blood vessels. The positive feedback loop causes more FSH + LH to be released. This increase leads to Graafian follicles to be produced. Follicle cells + oocytes are in the ovaries which take on an arrangement known as the Graafian follicle. A spike in FSH + LH leads to ovulation. The oocyte w/ Graafian follicles inner ring is a single follicle which enters the Fallopian tube soon after ovulation. These remain in the ovary which begin to secrete progesterone. These fill the wound area after ovulation. This forms a glandular structure - corpus luteum which is active for 10-12 days after ovulation if fertilization does not occur. High levels of estradiol + progesterone causes a negative feedback signal to the hypothalamus to prevent GnRH. The corpus lutes breaks down which leads due to a decline in the above hormones. As these fall, the endometrium ruptures + menstruation begins. The drop signals hypothalamus begins to secrete GnRH leading to another menstrual cycle. Uterine cycle controls prep. for lining of uterus. Ovarian cycle - production + release of eggs.
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D3.1.6 - The process of fertilization
The fusion of a sperms cell membrane w/ an egg cell membrane, entry to the off go the sperm but destruction of the tail + mitochondria. The dissolution of nuclear membranes of sperm + egg nuclei + participation of all condensed chromosomes in a joint mitosis to produce 2 diploid nuclei.
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D3.1.7 - In vitro fertilization
Normal secretion of hormones is suspended + artificial doses of hormones induce super ovulation. Eggs are harvested from the females ovaries after taking hormone therapy which suspends her natural menstrual cycle. Harvested eggs are mixed w/ sperm cells in separate culture dishes.
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D3.1.8 - Sexual reproduction in plants
The production of gametes inside ovules + pollen grains, pollination, pollen development + fertilization to produce an embryo.Reproduction in flowering plants in flowering plants is sexual, even if a plant species is hermaphroditic.
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D3.1.9 - Insect pollination
Table + image on 698.
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D3.1.10 - Cross-pollination in plants
There are different maturation times for pollen + stigma, which ensures self-pollination cannot occur.
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D3.1.11 - Self-incompatibility mechanisms
Self-pollination leads to inbreeding, which decreases genetic diversity + vigour. Genetic mechanisms in many plant species ensure a male + female gametes fusing during fertilization are from different plants.
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D3.1.12 - The role of seeds (distinguish seed dispersal from pollination)
Seed dispersal - once a successful double fertilization has occurred, a seed will begin to develop which leads to fertilization w/ in an ovary will lead to a diff. seed. When conditions become favourable seeds germinate. A seed contains a small plant embryo + food reserves which are called endosperm tissue which are transferred to the plant embryo through cotyledons. Seeds germinate by absorbing water through a process - imbibition. The rate of cell respiration + protein synthesis greatly increases following imbibition as the embryonic plant prepares to emerge from the seed coat. The radical is the portion of the embryo which emerges first.
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D3.1.13 - Developmental changes during puberty
In the hypothalamus of the brainstem increases GnRH which targets the pituitary gland which secretes FSH + LH. These 2 hormones are called gonadotropins because the target tissue is the gonads. Tables on 702.
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D3.1.14 - The production of gametes
Production of spermatozoa occurs in the testes which are located outside the body to provide a cool temperature. Inside each testes spermatogenesis occurs in small tubes - seminiferous tubules, near outer wall of these tubes are spermatogonia. These undergo mitosis + meiosis. Meiosis I takes place w/ 2 resulting cells. Then meiosis II occurs where chromatids are separated. Four haploid cells are produced. Now these cells differentiate into motile spermatozoon. These develop the flagellum + an acrosome which is developed in the seminiferous tubules - Sertoli cells. Once differentiated they detach and move through the lumen to a storage area of the testis - epididymis. Oogensis occurs w/ oogonia undergoing mitosis until they grow into primary oocytes. W/ in these are follicle cells which also undergo mitosis. These surround each primary oocyte + entire structure is called a primary follicle. A few of the primary follicles finish meiosis I during each menstrual cycle. The 2 haploid cells arising from a primary follicle are not the same in size. One is called the first polar body which is a reservoir for half the chromosomes. The polar bodies later degenerate the other is a secondary oocyte. Increase in fluid between the 2 follicle cell layers create a bulge on the surface of the ovary leading to ovulation. Table on 707.
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D3.1.15 - Preventing polyspermy
The acrosome reaction allows a sperm to penetrate the zone pellucid and the cortical reaction prevents other sperm from passing through.
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D3.1.16 - Embryo development
Embryo at the stage of reaching the uterine cavity is called a blastocyst. The trophoblast helps form the foetal portion of the placenta. The inner cell mass becomes the body of the embryo and is at one end of the blastocyst also is a fluid-filled cavity. The embryo eventually stops moving along the endometrial tissue which is called implantation.
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D3.1.17 - Pregnancy testing
Human embryos produce a hormone - human chorionic gonadotropin which is produced by the trophoblast layer. hCG enters the bloodstream of the mother allowing continuation of the corpus luteum w/ in the mother's ovaries. B-lymphocytes produce one type of antibody which recognize hCG as an antigen. The antibodies produced = monoclonal antibodies. The urine of a pregnant female contains hCG so the anti-hCG antibodies bind to the hCG + colour change occurs.
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D3.1.18 - The role of the placenta
Placenta forms from the trophoblast layer of the blastocyst. Placenta is a large pancake-shaped structure. The side closer to the uterine wall is made of connective tissue + blood vessels formed from mother. Side closer to the embryo is formed by the embryo + contains connective tissue + blood vessels. On the foetal side is the umbilical cord which is covered by 3 foetal blood vessels. 2 blood vessels w/ in umbilical cord carries foetal blood to the placenta. The blood w/ in 2 vessels is deoxygenated + carries waste products. This foetal blood exchanges materials w/ the maternal bloodstream, + the third blood vessel returns the blood to the foetus. Table + image on 711.
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D3.1.19 - Pregnancy and childbirth
The hormone progesterone maintains pregnancy + signalling when it's time for birth. As the foetus reaches full term, less progesterone is secreted by the placenta which signals birth to begin. Parturition is part of mammalian homeostasis. Contraction occur w/ increasing contractions by positive feedback. Oxytocin produced by the hypothalamus + secreted by the pituitary gland. When it's time for parturition, a decreased secretion of progesterone stimulates the pituitary is stimulated to secrete a small amount of oxytocin. Their receptors in the muscle of the uterus respond to the first contraction which signals more oxytocin to be released.. This happens repeatedly more and more frequent and intense until birth has occurred. Termination occurs as there is no longer anything to contract on.
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D3.1.20 - Hormone replacement therapy
Menopause is the period in a females life when her menstrual cycle becomes less predictable + stops. The reason is that ovaries stop producing estradiol + progesterone. Some females alleviate symptoms using hormone replacement therapy in the form of oestradiol.
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D2.3.2 - Water movement in relation to solute concentration
Hypertonic: surrounded by a solution that is higher in solute and lower in water relative to the cytoplasm. Hypotonic: surrounded by a solution that is lower in solute particles. Isotonic: equal concentration of solute in and out of the cell.
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D2.3.3 and D2.3.4 - Hypotonic and hypertonic solutions and osmosis
Aquaporins: hydrophilic tunnels through the cell membrane that polar water molecules pass through. If there is no net movement - dynamic equilibrium.
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D2.3.5 - Water movement without cell walls
Animal cells have no cell wall - osmosis has an effect on these cells. Ex. Red blood cells are placed in a high solute concentration so due to high levels of solute particles, water moves out of the cell. With mo cell walls present. The cell shrinks immediately resulting in crenation. If placed in hypotonic environment. the concentration will become closer to equal - swelling of red blood cells to the point of bursting. Adaptions have evolved to prevent this swelling and shrinkage - the contractile vacuole which collects excess water from the interior of the cell and empties it into the surrounding environment.
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D2.3.6 - Water movement with cell walls
Hydrostatic pressure: pressure that a fluid exerts in a confined space, against the boundary of space. In plant cells. the pressure is exerted against the cell walls and is turgor pressure. The incoming water swells the cell and pressed the cell membrane against the rigidd cell wall. Most plants develop turgor pressure to maintain their shape and remain upright. When water is lost from a plant cell, the cell membrane and the cytoplasm shrink from the cell wall - plasmolysis. When turgor pressure is lost, plasmolysis occurs + plant wilts leading to death.
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D2.3.7 - Isotonic solutions
Intravenous fluids (IV) fluids are used in medical conditions for maintain a balance of the solutes that exist in the solutions in our cells called intracellular fluids and outside called extracellular fluids. If ECF have a greater solute than ICF water will leave the body cells resulting in shrinking then crenation. If ECF has a lower concentration than solutes than ICF water will enter the cells resulting in swelling and bursting. If ECF and ICF are isotonic, a dynamic equilibrium is painted and there will be no net movement. IV solutions differ based on the medical condition - most are isotonic.
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D2.3.8, D2.3.9 an D2.3.10 - Water movement through plants
It is impossible to measure the absolute quantity of potential energy of water so values relative to pure water at atmospheric pressure and 20 degree C are used + kPa. Water potential is never positive. Water potential is represented by a greek letter psi with a w subscript.
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D2.2.1 - Phenotype
Gene expression - process of reading a gene + building a protein that will be used by the organism. Gene expression relies on transcription + translation. Types of proteins our cells build determine our phenotype.
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D2.2.2 - Regulation of transcription
The promoter region is a sequence of dNA indicating the gene's starting point. The enzyme in charge of transcription = RNA polymerase. + it attaches to the promoter region along w/ transcription factors. - proteins that bind to the promoter regions + regulate transcription. Promotor proteins are an example as they encourage RNA polymerase to attach to the DNA + start transcription. RNA polymerase then moves along to make an mRNA copy + detaches at the end of the gene. The mRNA then leaves the nucleus to be translated. We do not express all our genes. There are transcription factors which turn transcription on/off. An enhancer region allows certain activator proteins to attach + encourage transcription. The repressor is not attached to the silencer region as it would block transcription.
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D2.2.3 - Degradation of mRNA to regulate translation
mRNA may persist for time periods from minutes to days before being broken down by nucleases. rendering an mRNA molecule useless is called mRNA degradation. At one end of mRNA is a protective cap w/ repeating adenine nucleotides. Exonucleases are able to chop up RNA by removing nucleotides. The decaying complex- enzymes that can remove the cap. Deadenylase complex - enzymes that can remove adenine nucleotides in the polyA tail.
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D2.2.4 - Epigenesis
Epigenesis - process which results in the formation of organs + specialized tissue from an undifferentiated cell. Ectoderm - forms tissues such as skin + brain. Mesoderm - forms tissues such as skeleton + circulatory system. Endoderm - forms tissues such as lungs + liver. Epigenetics depends on genetic factors on the expression of genes. DNA methylation is a process by which a methyl group is added to a DNA nucleotide. The methyl groups act as epigenetic tags. This makes the gene inaccessible to the RNA polymerase. The gene will not be transcribed - not expressed - transcriptional silencing. Embryonic cells are cells that are not differentiated yet which have DNA which is not methylated. These are totipotent cells which can become any category of cell.
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D2.2.5 - Genome, transcriptome and proteome
No cell expresses all of its genes. The pattern of gene expression in a cell determines how it differentiates. All the RNA that a cell makes is its transcriptome. Proteome = all proteins in a cell.
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D2.2.7 - Epigenetic inheritance
The possibility of phenotypic changes in a cell or organism being passed on to daughter cells or offspring w/ out changes in the nucleotide sequence of DNA. This can happen if epigenetic tags, such as DNA methylation or histone modification, remain in place during mitosis/meiosis. Epigenetic modifications are reversible, most are erased but can be passed on, the DNA code is not modified by epigenetics.
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D.2.2.6 - Methylation
Methylation in the DNA of a promotor represses transcription so therefore expression of the gene downstream. Methylation of amino acids in histones can cause transcription to be repressed or activated. These methyl groups are epigenetic tags which tun transcription on/off.
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D2.2.8 - Environmental effects
Alteration of methyl tags on DNA in response to air pollution. DNA methylation has been measured in white blood cells. Diff. methylation patterns in the genes of children depending on whether their mother was exposed to high or low levels on PAHs in the air. Females living closer to major roads have different methylation patterns in the DNA responsible for the placenta.
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D2.2.9 - Removal of epigenetic tags
PGCs are formed inside an individual when they are developing foetus. PGCs their epigenetic tags removed by epigenetic reprogramming. Imprinted genes are those that have been silenced in only one of two copies - maternal or paternal. Tigers + lions can produce ligers. Imprinted genes for growth seem to function differently in each species so when they are mixed there are complications. Ligers can grow to an enormous size - due to genes from the father that affect growth being switched on allowing the offspring to grow. If the hybrid has opposite parents, larger sizes do not occur showing that it matters which genes come from the mother + which comes from the father.
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D2.2.10 - Monozygotic twins
Heterozygotic twins form when 2 separate eggs are fertilized at the same time by different sperm cells. Monozygotic twins are formed from the same zygote but 2 embryos form. Even w/ twins having the same genomes does not mean they are affected by the same things. DMRs allow researchers to find out whether disease is connected to differences in epigenetics. When comparing methylation patterns there are few differences in epigenetics. In adult twins, the differences in methylation patterns increase. The difference is larger in twins who grew up in diff. environments compared to those who grew up in the same environment.
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D2.2.11 - External factors
For the process of insulin to work, the gene for insulin needs to be actively transcribed + translated into insulin when blood sugars are high. The presence of glucose triggers transcription of the insulin gene INS. When lactose is present, Escherichia coli produces an enzyme lactase. If no lactose is present as a food source, the relevant digestive enzyme does not need to be produced. A zone of DNA acts as a binding site for the lac repressor. This binding site is called the operator + as long as the lac repressor is stick to this sequence of DNA it acts as a road block + stops the RNA polymerase from latching on + transcribing the genetic code. When lactose arrives it binds to the lac repressor + deactivates it so it detaches from the operator + allows RNA polymerase to transcribe the genetic code. There is more than one gene for lactase + the promoter region, operator + gene sequencing along the DNA make up the lac operon.
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D2.1.1 - Generating new cells
In all living organisms, a parent cell - often referred to as a mother cell - divides to produce two daughter cells.
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D2.1.2 - Cytokinesis
In an animal cell a ring of contractile actin + myosin proteins pinches a cell membrane together to split the cytoplasm, whereas in a plant cell vesicles assemble sections of membrane and cell wall to achieve splitting.
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D2.1.3 - Cytoplasm division
Division of the cytoplasm usually equal + both daughter cells must receive at least one mitochondrion + any other organelle that can only be made y dividing a pre-existing structure. Oogensis in humans + budding yeast are examples of unequal cytokinesis.
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D2.1.4 - Nuclear division
Nuclear division is needed before cell division to avoid production of nucleate cells. Mitosis maintains the chromosomes number + genome of cells, whereas meiosis halves the chromosome number + generates genetic diversity.
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D2.1.5 - DNA replication
After replication each chromosome consists of 2 elongated DNA molecules held together by a centromere. DNA replication occurs in the S phase.
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D2.1.6 - DNA condensation and chromosome movement
Histones help organize DNA which is coiled then supercoiled so could are on top of each other + form a compact pair of chromatids. When DNA is associated w/ histone proteins is referred to as chromatin. The astral microtubules reach out of the centroseom. The kinetochore microtubules attach to the centromere of the chromosome where 2 sister chromatids are attached. the overlap microtubules are not attached to the chromosomes but beside them, between are motor proteins which push the microtubules in opposite directions. When a cell is ready to separate , motor proteins overlapping microtubules become active.
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D2.1.7 - Mitosis
Before cell division occurs is a phase - interphase. In this the cell grows + prepares to divide. The following phases then occur: prophase, metaphase, anaphase, telophase.
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D2.1.8 - Identifying the phases of mitosis
Identify phases of mitosis by characteristics.
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D2.1.9 - Meiosis
Meiosis produces gametes. Meiosis is a reduction division. Meiosis produces haploid nuclei. This includes: Prophase I, Metaphase I, Anaphase I, Telophase I, Prophase II, Metaphase II, Anaphase II, Telophase II.
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D2.1.10 - Non-disjunction
Down syndrome is caused by an extra chromosome 21 resulting in 47 chromosomes which arises from non-disjunction.
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D2.1.11 - Genetic diversity
Meiosis generated genetic diversity by random orientation of bivalents + by crossing over.
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D2.1.12 - Cell proliferation
Meristems are areas of special tissue found in plant cells. These divide rapidly to grow the plants. Apical + lateral are 2 types of meristematic tissue. Skin is an example of cell proliferation during routine cell replacement + during wound healing.
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D2.1.13 - The cell cycle
Cell proliferation is achieved using the cell cycle. Students should understand the sequence of events including G1, S + G2 as the stages of interphase followed by mitosis + then cytokinesis.
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D2.1.14 - Interphase
Longest phase of the cell cycle is interphase. In this are smaller phases - G1, S + G2. G1 = cell growth. Then S which replicates DNA. G2 = cell grows + makes preparations for mitosis.
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D2.1.15 - Cyclins
Cyclins are a group of proteins that control the cells progression through the cell cycle. Cyclins bind to cyclin-dependent protein kinases so kinases acts as an enzyme. These activated enzymes then cause the cell to move from G1 to the S phase, then to the G2 phase to the M phase. Some cells pause during the G1 + enter the G0 phase which is a non-growing state. G1 cyclin tells the cell to grow + get ready to replicate DNA. ITs introduced during the first growth phase. Mitotic cyclin tells the cell to start making the microtubules that will form the spindle fibres for mitosis.
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D2.1.16 - The effect of mutations
Cancer cells undergo extremely rapid + uncontrolled reproduction w/ little differentiation. The result is a mass of cells. Oncogenes are sections of genes that can mutate/be expressed at abnormally high levels. These contribute to a cell becoming a cancer cell. Oncogenes can cause cells to divide more frequently than they should. a cell that can turn into a oncogene is a proto-oncogene. These cells have their death pre-programmed into their DNA so their materials can be recycled. This programmed death apoptosis. Oncogenes may mutate due to a mutagen. Healthy cells have specialized genes called tumour suppressor genes which code for proteins that can regulate the cell cycle.
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D2.1.17 - Tumour growth
A primary tumour occurs at the original site of cancer. A secondary tremor is a metastasis which is a cancerous tumour that has spread from the original location to another part of the organism. An example is a brain tumour w/ cancer cells. A tumour is benign if nothing is spreading to the rest of the body. A tour is malignant is the cells rupture the organ they are in + start to spread to the rest of the body. This can cause tumours to grow in tissues far from the primary tumour. Oncologists try to detect cancerous growths as early as possible. Once cancer metastasizes, it is very difficult to treat.
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D1.3.1 - Gene mutations
Mutation = random, rare change in genetic material. 3 types include substitutions, insertions and deletions. Substitution = replacement. Insertion = addition. Deletion = removal. When just one nucleotide is involve it is a point mutation. The locus of gene GNAT2 controls transducer which enables colour vision. A mutation of this gene stops an individual to make this properly so they cannot see.
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D1.3.2 - Base substitutions
A base substitution mutation - single lets changed. A gene altered any one letter by a base substitution = a single-nucleotide polymorphism. Due to degeneracy of the genetic code they may or may not change a single amino acid in a polypeptide. Sickle cell disease arises from a mutation of a red blood cell which develops a sickle.
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D1.3.3 - Insertions and deletions
Huntingtons disease is caused by an insertion mutation where multiple copies are added to the gene. This is known as a trinucleotide repeat expansion. W/ non-multiples of three occurs w/ an insertion/deletion is called a frameshift. Chemokines are chemical signals which tell the leucocytes which way to go in order to find invaders.
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D1.3.4 - Mutagens and replication errors
If exposed to ionized radiation/mutagens can modify the code + cause health threats. Mutations can also just be caused by errors in DNA.
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D1.3.5 - Location of mutations
Mutations can occur anywhere in the base sequence of a genome but some bases have higher probability of mutating than others. No natural mechanism is known for making a deliberate change to a particular base w/ the purpose of changing a trait. Satellite DNA is an example of non-coding DNA used for structural purposes - but high rates of mutations occur in satellite DNA.
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D1.3.6 - Mutations in germ cells and somatic cells
Mutations can have diff. effects if it is a germ or somatic cell. Germ cells use meiosis to produce gametes, somatic cells use mitosis to grow tissues + organs. If a mutation occurs in a germ cell, it can be passed onto generations. Cells involved in passing on genetic info to offspring make up the organisms germ line. IF a mutation occurs a somatic cell, it will not be passed on to the next generation.
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D1.3.7 - Genetic variation
Gene mutation is the original source of all genetic variation. Some mutations are harmful/neutral, but in some species they can be used long term for evolution by natural selection. There is a mutation that helps digestion.
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D1.3.8 - Gene knockout
Human Genome Project. Gene knockout involves rendering a gene unusable to see the effects it has on the organism. We use knockout organisms such as mice to do this. We test drugs on model organisms to see if they are safe for humans.
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D1.3.9 - CRISPR-Cas 9 gene editing
CRISPR-Cas 9 uses a Cas protein - Cas9 enzyme which cuts DNA. The second part is the guide RNA which is generated in a lab to match any desired target sequence. The result is the ability to remove/replace genetic sequences. This can help solve disorder such as Huntingtons disease or sickle cell disease, but also presents challenges w/ future generations etc.
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D1.3.10 - Conserved and highly conserved sequences
Conserved sequences - show minimal changes. Highly conserved sequences shoe almost/no changes. A hypothesis for the mechanism is the functional requirements for the gene products + another hypothesis is slower rates of mutation. Phenomenon of eliminating harmful variations of genes is a natural selection called purifying selection/negative selection. Mutation rate refers to how many changes there are in a genetic sequence over time.
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D1.2.1 - The synthesis of RNA
Ribosomes are essential to protein synthesis (cytoplasm) RNA communicates w/ DNA. Transcription = synthesis of RNA using the base sequence in DNA as a template. Transcription begins w/ an area of DNA unzipping. 2 complementary strands of dNA are now single stranded. Only 1 of 2 strands of DNA are used to create the mRNA. This is called template strand. RNA polymerase binds to a promoter sequence on the template strand. This enzyme links the RNA nucleotides to form the RNA strand.
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D1.2.2 - Hydrogen bonding and complementary base pairing
RNA polymerase breaks the H bonds between the 2 strands of DNA. As RNA polymerase moves along, RNA nucleotides float into place by CBP. Instead, adenine pairs w/ uracil.
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D1.2.3 - DNA templates
Single DNA strands can be used as a template for transcribing a base sequence, w/ out the DNA base sequence changing. In somatic cells that do not divide, such sequences must be conserved through the life of a cell.
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D1.2.4 - The expression of genes
Not all genes are expressed at any given time + transcription being the first stage of gene expression, is a keys stage at which expression of a gene may be switched on/off.
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D1.2.5 - The synthesis of polypeptides
Base sequence of mRNA is translated into he amino acid sequence of a polypeptide.
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D1.2.6 - RNA and ribosomes
mRNA binds to the smallest unit of the ribosome + 2 tRNAs can bind simultaneously to the large subunit.
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D1.2.7 - RNA complementary base paring
Any set of 3 bases found in dNA that determines the identity of 1 amino acid is called a triplet. When a triplet is found in an mRNA molecule it is a codon. An anticodon determine which of the 20 amino acids are attached to the tRNA.
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D1.2.8 - The genetic code
W/ 3 bases coding for an amino acid there are 64 possible combos. This is an adequate number of combos to provide a code for all the amino acids. The genetic code is degenerates for each amino acid there may be more than one codon. The genetic code is universal so all organisms share the same code.
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D1.2.9 - mRNA codons
Table on 595.
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D1.2.10 - Producing a polypeptide chain
As the ribosome coordinates the functioning of the mRNA + tRNA at the mRNA ribosomal complex, the 2 subunits golf the mRNA + tRNA close so the amino acids can be connected by peptide bonds to produce the specific polypeptide required. This is called elongation + produces a polypeptide chain.
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D1.2.11 - Changing the protein structure
Sickle cell disease is an example of a single point mutation which changes the shape of haemoglobin. When eh shape changes.
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D1.2.12 - Directionality
DNA polymerase assembles in a 5' to 3' direction. The 5' ends of free RNA nucleotides are added tot eh 33' end of the RNA molecule being synthesized. The mRNA is read in the direction of 5' to 3' to produce the polypeptide chain at the ribosome.
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D1.2.13 - Initiating transcription
RNA polymerase must first combine w/ a region of DNA called a promoter. This is a section of DNA that is not transcribed. Transcription factors are proteins that play a role in the regulation of the transcription process. The terminator is what ends transcription.
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D1.2.14 - Non-coding sequences
99% of our DNA does not provide instructions for making proteins. Dan that does not code for proteins are: regulators of gene expression - promoters, enhancers, silencers + insulators. Genes for rRNA + tRNA formation. Telomeres. Introns.
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D1.2.15 - Post-transcriptional modification
The removal of introns + splicing together exons to form mature mRNA + addition of 5' caps and 3' polyA tails stabilize mRNA transcripts.
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D1.2.16 - Alternative splicing of exons
Alternative splicing of transcripts of the troponin T gene in foetal + adult heart muscle is an example. A particular exon in the foetus is included in the mature mRNA produced by this gene which is not included in mature mRNA produced by the gene in the adult. The exon included in the foetal cardiac muscle makes the heart more sensitive to calcium than adult cardiac muscle.
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D1.2.17 - Initiating translation
The small ribosome attaches to the subunit to the 5' terminal of mRNA. movement to the start codon, the initiator tRNA + another tRNA + attachment of the large subunit.
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D1.2.18 - Modifying polypeptides
Many polypeptides must be modified before they can function. Insulin + its precursor - pre-proinsulin is produced by the pancreas, A signal peptide is removed as the pre-proinsulin enters the ER to produce proinsulin. Proinsulin is then exposed to enzymes that break peptide bonds. These enzymes result in the removal of a section of peptides known as C peptide.
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D1.2.19 - Recycling amino acids
The protein is the entire set of proteins that can be expressed by a cell, tissue or organism. Proteases can degrade proteins by breaking the peptide bonds. This converts a protein to its component amino acids. Eukaryotic cells rid themselves of damaged/ un-needed cells in a unique way. They mark these proteins w/ a chemical - ubiquitin. These are a signal to the cell to destroy these proteins. The cellular organelle which degrades a marked protein is the proteasome. The marled protein enters one end of the proteasome + amino acids exit the other end. The free amino acids can thence reused by the cell in the process of protein synthesis.
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D1.1.1 - The role of DNA replication
A polymer is composed of monomers called nucleotides. Each nucleotide has a 5-carbon sugar - deoxyribose, a phosphate group + a nitrogenous base. DNA must be duplicated for reproduction. DNA duplicates through DNA replication.
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D1.1.2 and D1.1.3 - Semi-conservative replication and complementary base paring
The replication process of DNA is said to be semi-conservative. Helices + a group of enzymes are called DNA polymerase. Free nucleotides which are not bonded, are free floating in the nucleoplasm. Once there are two separate strands, the unpaired nucleotides now are used as a template. Once it's unzipped, there are CBPs that form. This occurs as a free nucleotide located one end of an opened strand then another arrives to join the first. These must join by covalently bonding together. A third nucleotide then joins and so on. The other strand occurs in the same way but in the opposite direction.
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D1.1.4 - Amplifying and separating DNA
Polymerase chain reaction + gel electrophoresis. PCR is a technique using a thermocycler which takes a small amount of DNA + copies all the nucleotides to make millions of copies of dAN. Primers are short polymers which are complementary to the nucleotides at one end of the target DNA. tHese provide a starting point of rDNA synthesis. Taq is a polymerase from a bacterium which lives in hot springs + can withstand high temperatures. W/ the addition of free nucleotides, all are mixed in a tube. Then the steps of PCR follow: Denaturation- mixture is heated to break hydrogen bonds. Annealing - mixture is cooled to allow primers to bind w/ nucleotides on both strands. Elongation - taq polymerase catalyses building of new DNA strands. Gel electrophoresis includes fragments of DNA to identify its origin. The gel is exposed to an electrical current, the biggest particles do not move easily through the gel so they get stuck to the wells. the smallest move through. Intermediate particles are disturbed in between.
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D1.1.5 - Application of amplifying and separating DNA
Process of matching an unknown sample of DNA w/ a known sample to see if they correspond = DNA profiling. (fingerprinting)
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D1.1.6 - DNA polymerase's
Each time a nucleotide is added, it attaches to the 3' carbons end. The chain is built 5' to 3' as DNA polymerase can only add nucleotides in this direction. The two backbones run antiparallel, one having 5' at the top the other having 3' at the top.
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D1.1.7 - Leading and lagging strands
Helices breaks hydrogen bonds connecting the two strands. The point which helices is working to unzip the DNA molecule is called a replication fork. On the strand from 3' to 5', there is a continuous pattern + is fast. This is the leading strand. Then there is the lagging strand which is much slower. this is discontinuous + requires DNA ligase. The lagging strand is assembles through fragments in the opposite direction. These are Okazaki fragments. Primer, primate = DNA polymerase III are required to form each Okazaki fragment + to begin the formation of the leading strand. The primer + primate are only needed for the reading strand as it is produced continuously. Once the fragments are assembled, DNA ligase attaches the sugar phosphate backbones of the lagging strand fragments to form a single DNA strand.
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D1.1.8 - Functions of specific enzymes and molecules
Helices - unwinds double helix. DNA primate - synthesizes RNA primer. RNA primer - marks the beginning of the replication process. DNA polymerase I - removes primer at end of replication + replaces it w/ DNA nucleotides. DNA polymerase III - synthesizes new strand by catalysing the addition of molecules in the 5' to 3' direction. DNA ligase - joins the ends of DNA segments + Okazaki fragments. Single -stranded binding protein - keeps bases from reforming hydrogen bonds between them after helices action.
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D1.1.9 - Removing mismatched nucleotides
DNA polymerase III checks for accuracy. It removes a mismatched nucleotide from the 3' end + reverses direction to resume the synthesis correctly.
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D2.3.1 - Water as a solvent
Water is the universal solvent. A solution is aqueous is water is the solvent. Salvation is the interaction of a solvent w/ a dissolved solute. When water is in a liquid state, hydrogen bonds are continually breaking, reforming + moving. Sodium chloride is solvated by polar solvents. The small positive charges on the hydrogen surround the negative ones on the chloride ions.
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D2.3.2 - Water movement in relation to solute concentration
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D2.3.1 - Maintaining the body's internal environment
Homeostasis is a regulatory mechanisms to keep certain factors w/ in preset limits, despite fluctuations w/ external environment. This includes internal body temp., pH of blood, blood glucose concentration, blood osmotic concentration. The human body's internal temperature is 37 degrees C.
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D3.3.2 - Negative feedback mechanisms
Negative feedback is used in homeostasis + returns homeostatic variables back to a set point from values above + below the set point. The nervous + endocrine systems work cooperatively to ensure homeostasis. Endocrine system - numerous glands to produce a variety of hormones.
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D3.3.3
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D3.3.4 - Type 1 and type 2 diabetes
Diabetes is characterized by hyperglycaemia + exists in 2 forms. Type 1: autoimmune disease where the immune system mistakenly destroys the beta cells in the pancreas which produce insulin. Risk factors: Family history, age. Treatment: controlled diet + injections of insulin. Type 2 diabetes: blood receptors which do not respond properly to insulin + cells do not take in sufficient glucose. In type 2 there is insulin resistance. Risk factors of type 2: family history, obesity, lack of exercise. Effects: blindness, kidney failure, nerve damage, increased risk of cardiovascular disease, poor wound healing.
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D3.3.5 and D3.3.6 - Body temperature control
Ectothermic animals - temperature equalizes w/ the environment. Endothermic - maintains a steady internal temperature. Thermoreceptors are located in the skin + in a portion of the brain - hypothalamus. Regulation of body temperature: thermoregulation. If body temperature rises above 37C, the hypothalamus sends impulses to the arterioles near the skin resulting in vasodilation. This means more blood travels through capillaries + more heat is released. Also initiatives perspiration (evaporation - breaking of hydrogen bonds could the body) If it falls below 37 C, vasoconstriction occurs so more blood is shunted to internal organs + less to skin. Less heat is released to the environment as capillaries receive less blood. Release of epinephrine in cold environments results in goosebumps (is a response for hairy animals but we developed an autonomic response) Thyroxine increases metabolic rate of all body cells to generate heat when peripheral thermoreceptors in the skin sense cold. Shivering also generates heat. Some animals in cold waters evolved blubber to insulate their internal organs. (form of adipose tissue) Newborns cannot shiver so instead have a higher proportion of fat called brown adipose tissue. Brown due to more mitochondria. when needed these begin cell respiration. Glucose is oxidized for generating body heat. Adults retain a small amount of this tissue. At a subconscious level, the cerebrum helps initiate behaviours to help stay warm.
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D4.1.7 - Sexual selection
Differences in physical + behavioural traits can be sings of overall fitness, this can affect success in attracting a mate + drive the evolution of an animal population. Females have cryptic colouration or dull/dark colours which blend in. When a bird has colourful feathers, to makes it difficult for it to fly as proteins + minerals are invested in these colours. This indicates the bird is healthy so females want to mate with him. When there is a morphological difference between males + females is called sexual dimorphism. Comp. between males for access to females = intersexual comp.
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D4.1.8 - Modelling selection pressures
John Endler's experiment: Female guppies show cryptic colouration which provides camouflage. Males have mosaic of spots. He carried out the exp. w/ 1 group in field + in 10 artificial ponds w/ controlled variables - some kept w/ predatory fish some w/ out. He found there are 2 opposing selective pressures: predation + sexual selection. He tested this by introducing predatory fish that eat guppies + some fish that were not predatory.
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D4.1.9 - Gene pools
A gene pool is all the genetic info. present in a population at a time. Inbreeding occurs when closely related organisms mate. Inbreeding narrows the gene pool. Allele frequency is a measure of the proportion of a specific version of a gene in a population. Gene pool normally are stable over time. New alleles however may be introduced due to mutation + old alleles may disappear when organisms die.
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D4.1.13 - The Hardy-Weinberg equation
To calculate the frequencies of alleles w/ in a population, the Hardy-Weinberg equation can be used. This uses p and q to denote the two allele frequencies. p + q = 1 so genotype frequencies are predicted by the Hardy-Weinberg equation: p^2 + 2pq + q^2 = 1. If one of the genotype frequencies is known, the allele frequencies can be calculated using the same equations.
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D4.1.14 - Genetic equilibrium
If genotype frequencies in a population do not. fit the Hardy-Weinberg equation, this indicated that 1 or more of the conditions is not met, for example mating is a non-random or survival rates vary between genotypes.
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D4.1.15 - Artificial selection
Humans breed organisms to increase desirable characteristics - artificial selection by selective breeding. Antibiotic resistant bacteria is an example of natural selection. this is an unintended consequence of human actions due to natural rather than artificial selection.
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D4.2.1 - Sustainability of natural ecosystems
There is evidence for some ecosystems persisting millions of years. A sustainable ecosystem supports itself w/ out outside influence. The Amazon rainforest became its own source of moisture, as transpiration from a vast area of dense plant life became sufficient to provide water for the rainforest.
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D4.2.2 - Requirements for sustainability
To be sustainable long-term, requirements must be met: sufficient supply of energy, recycling of nutrients, genetic diversity, climatic variables remaining w/ in tolerance levels.
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D4.2.3 - Tipping points
There is a need for a large area of rainforest for the generation of atmospheric water vapour by transpiration, w/ consequent cooling, air flows and rainfall. Include uncertainty over the minimum area of rainforest that is sufficient to maintain these processes. (must be able to calculate percentages)
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D4.2.4 - Mesocosms
Mesocosm = self-contained system that provides a living environment for organisms. They can be set up in open tanks but sealed glass vessels are preferable due to exit + entry of matter can be prevented but energy transfer is still possible. Aquatic or microbial ecosystems are likely to be more successful than terrestrial ones.
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D4.2.5 - Keystone species
Keystone species - organisms of any type which plays an important role in the biodiversity of their ecosystem regardless of their population size. There is a large impact on community structure of keystone species + risk of ecosystem collapse if they are removed. Effect of losing a a keystone species is a trophic cascade.
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D4.2.6 - Sustainable harvesting of natural resources
Sustainability depends on the rate of harvesting being lower than the rate of replacement. An example is the Chilean sea bass. This fishing technique is called long lining. A plant example is the Black cherry trees. These are sought for furniture. These are now removed sustainably.
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D4.2.7 - Sustainability of agriculture
Soil erosion + leaching of nutrients, supply of fertilizers + other inputs, pollution due to agrochemicals + carbon footprint are all considered when sustaining agriculture.
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D4.2.8 - Eutrophication
Eutrophication results from leaching of nitrogen + phosphate fertilizers including increased biochemical oxygen demand. (BOD) Eutrophication = leaching of compounds into nearby bodies of water. (?)
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D4.2.9 - Biomagnification
Biomagnification - harmful substances in the environment build up in the organisms towards the top of a food chain. Mercury accumulating in food chains are rare + located near industries. but now they are at the top of aquatic food chains. Increased levels of toxins accumulate in the tissues of consumers in higher trophic levels. DDT is a synthetic insecticide which was used against mosquitos. Mosquitos became resistant + marine environments consumed it. This caused production of thin-shelled eggs in birds so the mother would break the egg as they sat on their young.
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D4.2.10 - Microplastic and microplastic pollution
Plastics are not biodegradable + are persistent in the natural environment. Microplastics - more than 5mm. Microplastics - less than 5 mm. Plastic items in the ocean get caught in large ocean cortices called gyres. This kills seat turtles, gets trapped on sea birds etc.
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D4.2.11 - Rewilding
Rewinding activities are aimed to restore + protect natural processes. Methods include reintroduction of apex predators + other keystone species, establishing wildlife corridors, stopping agriculture, minimizing human influence on an ecosystem. Hinewai Reserve in New Zealand has the goal to foster regeneration of native vegetation + wildlife. Strategy used is to allow nature to take its own course.
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D4.2.12 - Ecological succession
Ecological succession - change over time in the species that live in the area - reason why some species replace others gradually. - triggered by changes in the abiotic factors. Primary succession = new land created + series of communities emerge, any one community prepares the land for the next type of community. Secondary succession = when an existing ecosystem is drastically altered by fire, flood/human intervention + remains of the previous ecosystem are used as a starting point for further changes.
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D4.2.13 - Primary succession
First living - pioneer species appear after new land is formed from volcanic lava. Often photosynthetic organisms which do not grow root systems, over a long period of time lichens + moss help build up soil that can be used by other producers. After hundreds of years, a climax community may develop.
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D4.2.14 - Cyclical succession
in some ecosystems there is a cycle of communities rather than a single unchanging climax community. Wood pastures are an example of this . Succession begins w/ growth of thorned, unpalatable thickets. some trees begin to grow using thicket as protection from herbivores. Then trees restrict the growth of the surrounding thicket. Trees then die of natural causes so it is an open pasture once again. Then the cycle begins again.
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D4.2.15 - Climax communities
Ecological succession proceeds w/ a series of species replacements until a particular stable community is formed. Final community is called a climax community. These are ecologically stable + does not change unless environmental conditions change/there is human interference. Human activities in an area can arrest the natural development of an ecosystem + reset the succession timeline to an earlier stage.
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D4.3.1 - Human activity and climate change
We live at the bottom of an ocean of air called the atmosphere. The greenhouse effect - the way the atmosphere retains heat + keeps planet warm. Energy is re-radiated in the form of infrared radiation. GHGs (methane + CO2) in Earth's atmosphere is the glass of a greenhouse. The climate change occurring is anthropogenic. Climate is patterns of temperature + precipitation. data from Antarctic ice cores shows a positive correlation between global temperatures + atmospheric carbon dioxide concentrations over years. This correlation does not prove that CO2 in the atmosphere increase global temperatures, although other evidence confirms the casual link.
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D4.3.2 - Global warming
When a marine organism dies it sinks to the bottom - benthic zone. Decomposers break down this material + produce CO2. If the surface is warmer, phytoplankton can produce more biomass, which can be passed along the food chain. Then more reaches the benthic zone so more CO2 is produced. This is a positive feedback loop as it amplifies. ability to reflect light is albedo. Light coloured = higher albedo. Carbon sinks trap organic matter + conditions prevent it from being fully decomposed. Permafrost is a type of soil that exists in very cold climates + is frozen. When we have higher temperatures the permafrost melts so the microbes become active + decompose the trapped organic matter so more CO2. It can also release methane. This is due to some methanogenic archaea.
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D4.3.3 - Tipping points
Warmer temperatures + decreased winter snowfall leading to increased incidence of drought + reductions in primary production in taiga, w/ forest growing + increases in the frequency + intensity of forest fires, which result in legacy carbon combustion. Carbon locked up in the soil + passed on is legacy carbon.
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D4.3.4 - Polar habitat change
Emperor penguins prefer to breed on sea ice. Landfast ice breaks up + detach from shore when summer arrives in December + warms the water. By then, the eggs have been incubated for 2 months by the males, have hatched so chicks begin to grow to find their own food. W/ global climate change, they are exposed to warmer temperatures so the ice separates earlier in the breeding season. Walruses prefer sea ice shelves as breeding grounds. The mother suckle their babies then dive into the water to get food. W/ melting ice there is reduced breeding grounds + less space to rear young.
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D4.3.5 - Ocean current change
Warmer surface water can prevent nutrient upwelling to the surface, decreasing ocean primary production + energy flow through marine food chains. The El Niño Southern Oscillation event occurs every 2 to 7 years. When there is not this event there are prevailing trade winds blowing air towards the west. Cold water is pushed which is full of nutrients so there is movement of nutrient-rich water from deeper parts of the ocean towards the surface which is called nutrient upwelling.
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D4.3.6 - Range shifts
When tree species move towards to poled it is called range migration. We do not know if this is from human-induced climate change. Birds are also migrating upslope. Tropical birds are very sensitive to heat so they go to higher altitudes to find cooler temperatures.
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D4.3.7 - Ecosystem collapse
Increased CO2 concentrations are the cause of ocean acidification + suppression of calcification in corals. Increases in water temperature are a cause of coral bleaching. Loss of corals causes the collapse of reef ecosystems.
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D4.3.8 - Carbon sequestration
There is active scientific debate over whether plantations of non-native tree species or rewinding w/ native species offer the best approach to carbon sequestration. Peat formation naturally occurs in waterlogged soils in temperature + boreal zones + very rapidly in some tropical ecosystems.
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D4.3.9 - Phenology
Photoperiod + temperature patterns are examples of variables which influence the timing of biological events such as flowering, bud first + bud set in deciduous trees, bird migration + nesting. Phenology = study of timing of periodical events such as flowers bursting.
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D4.3.10 - Disruption of phenological events
In an ecosystem temperature may act as the cue in one population + photoperiod may be the cue in another. Trophic mismatch if migrating + synchronized peak resource availability fall out of sync. (finish when lesson happens)
