Bio Exam Flashcards
Types of evidence of Evolution
Fossils: Preserved remains (body fossils) provide direct evidence of ancestral forms and include bones, teeth, shells, leaves, etc. Traces provide indirect evidence of ancestral forms and include footprints, tooth marks, burrows, and feces (coprolite).
Transitional fossils: They establish the links between species by exhibiting traits common to both an ancestor and its predicted descendants
Selective breeding: Selective breeding provides evidence of evolution as targeted breeds can show significant variation in a (relatively) short period.
Homologous structures: Homologous structures are similar physical features in organisms that share a common ancestor, but the features serve completely different functions.
Speciation: The evolutionary process by which two related populations diverge into separate species is called speciation
Hierarchy of different taxa
Kingdom Katy
Phylum Perry
Class Comes
Order Over
Family For
Genus Grape
Species Soda
Homologous vs Analogous
Homologous structures: those that are similar in shape in different types of organisms. The structural similarities imply a common ancestry. The pentadactyl limb in vertebrates is an example of a homologous structure. Despite the obvious differences, all the organisms share the same bones. For example, the bones may vary in size and shape, but all vertebrates have five-fingered ‘hands’ at the end of each limb: This pattern is an indication of a common ancestor.
Analogous structures are features of different species that are similar in function but not necessarily in structure and which do not derive from a common ancestral feature (compared to homologous structures) and which evolved in response to a similar environmental challenge.
Variation leading to natural selection
Natural selection requires variation among members of a species in order to differentiate survival (variation needed for selection).
- Mutations – Changing the genetic composition of gametes (germline mutation) leads to changed characteristics in offspring
- Meiosis – Via either crossing over (prophase I) or independent assortment (metaphase I)
Crossing over: The exchange of genetic material occurs between non-sister chromatids at points called chiasmata. As a consequence of this recombination, all four chromatids that comprise the bivalent will be genetically different.
Independent assortment: When homologous chromosomes line up in metaphase I, their orientation towards the opposing poles is random. The orientation of each bivalent occurs independently, meaning different combinations of maternal/paternal chromosomes can be inherited when bivalents separate in anaphase I
- Sexual reproduction – The combination of genetic material from two distinct sources creates new gene combinations in offspring
- Inherited Variation – There is genetic variation within a population which can be inherited
- Competition – There is a struggle for survival (species tend to produce more offspring than the environment can support)
- Selection – Environmental pressures lead to differential reproduction within a population
- Adaptations – Individuals with beneficial traits will be more likely to survive and pass these traits on to their offspring
- Evolution – Over time, there is a change in allele frequency within the population gene pool
Structures, types and examples of carbohydrates, proteins and lipids
Carbohydrates:
Most abundant organic compound found in nature, composed primarily of C, H, and O atoms in a common ratio – (CH2O)n
Principally function as a source of energy (and as a short-term energy storage option)
Also important as a recognition molecule (e.g. glycoproteins) and as a structural component (part of DNA / RNA)
Lipids:
Non-polar, hydrophobic molecules which may come in a variety of forms (simple, complex or derived)
Lipids serve as a major component of cell membranes (phospholipids and cholesterol)
They may be utilized as a long-term energy storage molecule (fats and oils)
Proteins:
Makeover 50% of the dry weight of cells; are composed of C, H, O, and N atoms (some may include S)
Major regulatory molecules involved in catalysis (all enzymes are proteins)
May also function as structural molecules or play a role in cellular signaling (transduction pathways)
Carbohydrates:
Carbohydrates are composed of monomers called monosaccharides (‘single sugar unit’)
Monosaccharides are the building blocks of disaccharides (two sugar units) and polysaccharides (many sugar units)
Most monosaccharides form ring structures and can exist in different 3D configurations (stereoisomers)
Lipids:
Lipids exist as many different classes that vary in structure and hence do not contain a common recurring monomer
However several types of lipids (triglycerides, phospholipids, waxes) contain fatty acid chains as part of their overall structure
Fatty acids are long chains of hydrocarbons that may or may not contain double bonds (unsaturated vs saturated)
Proteins:
Proteins are composed of monomers called amino acids, which join together to form polypeptide chains
Each amino acid consists of a central carbon connected to an amine group (NH2) and an opposing carboxyl group (COOH)
A variable group (denoted ‘R’) gives different amino acids different properties (e.g. may be polar or nonpolar, etc.)
Enzyme activity (effect of different variables)
Temperature:
Low temperatures result in insufficient thermal energy for the activation of an enzyme-catalyzed reaction to proceed
Increasing the temperature will increase the speed and motion of both enzyme and substrate, resulting in higher enzyme activity
This is because a higher kinetic energy will result in more frequent collisions between the enzymes and substrates
At an optimal temperature (may vary for different enzymes), the rate of enzyme activity will be at its peak
Higher temperatures will cause enzyme stability to decrease, as the thermal energy disrupts the enzyme’s hydrogen bonds
This causes the enzyme (particularly the active site) to lose its shape, resulting in the loss of activity (denaturation)
pH:
Changing the pH will alter the charge of the enzyme, which in turn will alter protein solubility and overall shape
Changing the shape or charge of the active site will diminish its ability to bind the substrate, abrogating enzyme function
Enzymes have an optimal pH (which may differ between enzymes) and moving outside this range diminishes enzyme activity
Substrate Concentration:
Increasing substrate concentration will increase the activity of a corresponding enzyme
More substrates mean there is an increased chance of enzyme and substrate colliding and reacting within a given period
After a certain point, the rate of activity will cease to rise regardless of any further increases in substrate levels
This is because the environment is saturated with substrate and all enzymes are bound and reacting (Vmax)
Membrane transport
Active transport:
Sodium-potassium pump restore resting potential in the axon following nerve impulse
Reuptake of neurotransmitters to the presynaptic neuron following synaptic transmission.
Removal of Ca2+ from presynaptic neuron following synaptic transmission
Simple diffusion:
Diffusion of NT across synaptic cleft
Diffusion of K+ ions out of axon in resting potential
Facilitated diffusion:
Opening of voltage gated Na+ and K+ channels in action potential
Opening of voltage-gated Ca2+ channels at presynaptic terminal
Na+ channels activated at post-synaptic terminal to propagate AP
Vesicle transport:
Influx of Ca2+ activates vesicles of neurotransmitters
Exocytosis of NT from presynaptic neuron to synaptic cleft
Role of peptide hormones
Peptide hormones play a prominent role in controlling energy homeostasis and metabolism. They have been implicated in controlling appetite, the function of the gastrointestinal and cardiovascular systems, energy expenditure, and reproduction.
Causes of respiratory diseases
- Radiation (X-rays)
- Ageing (senescence)
- Pollution (e.g. smog)
- Environment (radon gas)
- Diseases (e.g. COPD)
- Genetics (family history)
- Occupation (e.g. miners)
- Asbestos (silicates)
- Tobacco (smoking)
- Smoke (secondhand)
Maintaining gas concentrations via the respiratory system
Because the gas exchange is a passive process, a ventilation system is needed to maintain a concentration gradient in alveoli
- Oxygen is consumed by cells during cellular respiration and carbon dioxide is produced as a waste product
- This means O2 is constantly being removed from the alveoli into the bloodstream (and CO2 is continually being released)
The lungs function as a ventilation system by continually cycling fresh air into the alveoli from the atmosphere
- This means O2 levels stay high in alveoli (and diffuse into the blood) and CO2 levels stay low (and diffuse from the blood)
- The lungs are also structured to have a very large surface area, so as to increase the overall rate of gas exchange
Process of in vitro fertilization
Down regulation: Drugs are used to halt the regular secretion of FSH and LH, which tops the secretion of estrogen and progesterone. Therefore, doctors can take control of the timing and quantity of egg production by the ovaries.
Superovulation: Involves using artificial doses of hormones to develop and collect multiple eggs from women. She is injected with large amounts of FSH to stimulate the development of many follicles. The follicles are treated by hCG, a hormone produced by a developing embryo. Egg is then collected prior to follicles rupturing.
Fertilization: Eggs are incubated in the presence of a sperm sample from male donor.
Implantation: Two weeks before implantation, she begins to take progesterone treatments to develop endometrium. Healthy embryos are selected and transferred into the female uterus. Multiple embryos are transferred for better luck of implantation. A pregnancy test is then taken 2 weeks after.
Role of the hormones insulin, glucagon, thyroxin and leptin
Thyroxin is secreted by the thyroid gland to regulate the metabolic rate and help control body temperature. It targets most body cells and effects the rate of protein synthesis, increases metabolic rate, increases heat production (e.g. increased respiration). Leptin is secreted by cells in adipose tissue and acts on the hypothalamus of the brain to inhibit appetite. It is produced by adipose cells (fat storage cells) and targets appetite control centre of the hypothalamus (in brain). It affects the increase in adipose tissue, resulting in the increase of leptin secretions into the blood, causing appetite inhibition and hence reduced food intake. If blood glucose is too high beta cells of pancreas produce something called insulin. Insulin stimulates uptake of glucose to cells, e.g: muscle. Insulin stimulates liver/fat cells to store glucose as glycogen, and leading to decrease in blood glucose. If blood glucose is too low, alpha cells of pancreas produce glucagon. Glucagon stimulates liver to break glycogen into glucose, and leads to increased blood sugar
Male and female reproductive organs
a. Uterus: provides protection, nutrients, and waste removal for developing fetus
b. Fallopian tubes: connects the ovary to the uterus, fertilization occurs here
c. Ovaries: eggs stored, develop, and mature. Produces estrogen and progesterone
d. Endometrium: develops each month in readiness for the implantation of a fertilized egg. Sheds during the menstrual cycle.
e. Cervix: Muscular opening to the uterus
f. Vagina: accepts penis during sexual intercourse and sperm is received.
a. Vas deferens: carries sperm to penis for ejaculation
b. Prostate gland: adds alkaline fluids that neutralize the vaginal acids
c. Urethra: delivers semen during ejaculation and semen for excretion
d. Penis: becomes erect to penetrate vagina during intercourse, delivers sperm to top of vagina
e. Seminal vesicle: adds nutrients like sugar for respiration and mucus to protect sperm
f. Epididymis: sperm is matured and stored here
g. Testis: produces sperm and testosterone
h. Scrotum: protects testes outside the body to maintain and lower optimum temp for sperm.
Blood clotting process
Wounds such as cuts to the skin causes opening through which pathogens can potentially enter the body. Blood clots at the site of a wound help prevent blood loss and the entry of pathogens. Platelets (small cell fragments) along with damaged tissue release clotting factors in response to a wound. Clotting factors cause a series of reactions which end with fibrin (a protein) fibres forming a mesh across the wound with. The fibrin fibres capture blood cells and platelets forming a clot. In the presence of fait the clot dries to form a scab with shields the healing tissue underneath.
Action potential graph (what is happening at each stage)
- Action potential is the reversal (depolarization) and restoration (repolarization) of the membrane potential as an impulse travels along it.
- The sodium-potassium pump (Na+/K+ pump) maintains the electrochemical gradient of the resting potential. Some K+ leaks out of the neuron (making the membrane potential negative, -70mv)
- In response to a stimulus (e.g. change in membrane potential) in an adjacent section of the neuron some voltage-gated Na+ channels open and sodium enters the neuron by diffusion.
- If a sufficient change in membrane potential is achieved (threshold potential) all voltage-gated Na+ channels open.
- The entry of Na+ causes the membrane potential to become positive (depolarization) The depolarization of the membrane potential causes the voltage gated Na+ channels to close and the voltage gated K+ channels open.
- K+ diffuses out of the neuron rapidly and the membrane potential becomes negative again (repolarisation)
- Before the neuron is ready to propagate another impulse the distribution of Na+ (out) and K+ (in) needs to be reset by the Na+/K+ pump, returning the neuron to resting potential.
- This enforced rest (refractory period) ensures impulses can only travel in a single direction
