Flashcards in AS Level Unit 2 Deck (134):
What is the middle of a chromosome called?
What are homologous chromosomes?
A pair of chromosomes, one from paternal and one from maternal with the same genes but different alleles
Name two ways in which meiosis allows the production of genetically different cells
Crossing over and independent segregation
What is a species?
A group of similar organisms that can reproduce to produce fertile offspring
A forest was cleared. Why did species diversity decrease?
Decrease in the variety of plants, fewer habitats and a decrease in food sources
What is a hierarchy?
Groups within groups and no overlaps between the groups
What is a phylogenetic group?
Grouped according to evolutionary relationships
Why is cytochrome C more useful than haemoglobin for studying how closely related different organisms are?
The structure of cytochrome C is similar in all organisms
How can antibiotics prevent the growth of bacteria?
Prevent a formation of the cell wall
Describe how bacteria can become resistant to antibiotics by vertical gene transmission
The genes are transmitted through cell replication
Why did doctors take a sample from many patients in the hospital?
So it's representative
What causes root pressure?
active transports of salts by the endodermis
Name a type of reaction that breaks down carbohydrates into their monomers?
Why is an arteriole described as an organ?
Made up of more than one tissue
Name all of the stages of taxonomy
Kingdom, phylum, class, order, family, genus and species
What is intraspecific variation?
differences within a species
Give two reason why the potometer does not truly measure the rate of transpiration
Water is used for support and water is used in photosynthesis
What is species diversity?
The total number of individuals in each species and the total number of individuals of all species
How does carbon dioxide in the air outside of the leaf reach Mesophyll cells inside of the leaf?
Carbon dioxide enters via the stomota and diffuses through air spaces down a concentration gradient
What monomers form a cellulose molecule?
What bonds join a cellulose molecule
Why is mitosis important in the life of an organism?
For growth and repair of cells and for asexual reproduction
Why is DNA a polymer?
More than one nucleotide
Name the three parts of DNA molecule
Hydrogen bonds, deoxyribose sugar and phosphate group
What does standard deviation show? 2 marks
The variation of data around the mean
No overlap means that it is not due to chance
Name three parts of a chloroplast
Granum, stroma and thylakoids
Give two ways in which courtship increases the probability of successful mating
How do bacteria become resistant strains?
A random mutation occurs, so resistant gene so the resistant bacteria survives and reproduces
How is the resistant gene passed on from one species of bacteria to another?
By horizontal gene transmission via conjugation where they plasmid/circular DNA is copied
What is genetic diversity?
Differences in DNA
Explain the advantage of cells completing the cell cycle in a short time
They can multiply rapidly
What is interspecific variation?
Differences between different species
Name an animal cell and its 2 adaptations
Squamous epithelial cell
Thin cytoplasm for a short diffusion pathway
It's long so it's got a large surface area
What are the lungs made up of? 3
Squamous epithelial tissue
What four things is the respiratory system made up of?
Lungs, trachea, bronchi and diaphragm
What is squamous epithelial tissue is made up of?
Name a plant cell
Palisade Mesophyll cell
How is the palisade Mesophyll cell adapted for photosynthesis?
It's got many chloroplasts and the large vacuole pushes the cytoplasm and chloroplasts to the edge of the cell
What two things are xylem tissue made up of?
Xylem vessels and parenchyma cells
What four things are leaves made up of?
Xylem and phloem, epidermis tissue and Mesophyll tissue
Name the four things that make up the shoot system
Leaves, buds, stems and flowers
What is the role of starch?
For energy storage in plants
Why is it good that is insoluble?
So water potential doesn't affect the cell so it won't swell and burst
What monomers is starch made up of and what bonds is it joined by?
Alpha glucose and glycosidic bonds
What is the structure of amylose?
Coiled so it's good for storage because it's compact
What is the structure of amylopectin and why is this good?
Long branched so enzymes can reach bonds quickly to release energy
What is the role of glycogen?
For energy storage in animals
What's monomers is glycogen made up of and what bonds are they joined by?
Alpha glucose and glycosidic bonds
What is the structure of glycogen?
Short branched so it is good for storage because it's compact
Will enzymes reach the bonds in starch or glycogen quicker?
What is the role of cellulose and where is it found?
Provides rigidity for structural support and it's in plant cell wall
What is the structure of cellulose? Three marks
Long unbranched, held together by hydrogen bonds bonds, forming microfibrils
In cellulose, how are the glucose monomers arranged?
Alternating glucose molecules rotated by 180°
How are glucose monomers arranged in starch?
The same way up
Name three parts of the liver in order
Hepatic vein, hepatic portal vein and hepatic artery
What are the two parts of the kidney in order?
Renal vein and renal artery
During which parts of the cell cycle are gene mutation is most likely to occur?
What is an allele?
A different variation of a Gene
Describe two features of the appearance of a chromosome
Two sister chromatids joined by a centromere
Suggest why only a few gametes only have a new combination of the new alleles
It's rare and infrequent
Comparing the base sequence of a gene provides more information than comparing the amino acid sequence for which the gene codes. Explain why.
Longer base sequence than amino acid sequence
How many bases code for an amino acid and what is this called?
What is crossing over?
The exchange of alleles between chromosomes
How is tissue fluid formed? 3 marks
High hydrostatic pressure forces water out of the capillary but leaves behind large proteins
How is tissue fluid returned to the circulatory system? 4 marks
There is a lower water potential in the capillary
due to plasma proteins
so water enters into the capillary by osmosis from high water potential to lower water potential
and the rest is returned by the lymphatic system
What is the Bohr affect?
That haemoglobins oxygen affinity is inversely related to the concentration of carbon dioxide
Describe what happens in DNA replication. 8 marks
1. DNA Helicase
2. Causes hydrogen bonds to break, separating the DNA strands
3. Each strand acts as a template
4. Free nucleotides attach to each strand
5. They are complementary base pairing (AT, CG)
6. DNA Polymerase joins nucleotides onto new strand
7. Hydrogen bonds reform
8. Known as semiconservative model as one strand is new and one strand is old
What five things happen in prophase?
1. Chromosomes condense
2. Centrioles move to opposite poles of the cell
3. Spindle fibres form
4. Nuclear envelope breaks down
5. Chromosome lie free in the cytoplasm
What two things happen during metaphase?
1. Chromosomes line up along the Equator of the cell
2. Spindle fibres attach to the centromeres
What three steps happen during anaphase?
1. Centromere divide, separating sister chromatids
2. Spindle fibres contract, pulling chromatids to opposite poles of the cell
3. Centromere first
What three things happen during Telophase?
1. Chromatids reach the opposite poles of the cell and uncoil
2. Nuclear envelope reforms around each set of chromosomes
3. Cytoplasm divides
What is produced at the end of mitosis?
Two genetically identical daughter diploid cells
What do you get at the end of Meiosis?
Four genetically unidentical daughter haploid cells
What is cancer?
The uncontrolled division of cells
How does radiation help treat cancer? 4 marks
1. Damages DNA
2. During S phase DNA is checked for damage
3. Damaged it DNAs stop cell replication and kills cell
4. Preventing tumour growth
How does chemotherapy help prevent cancer? 3 marks
1. Effects enzymes involved in DNA replication
2. Stops S-phase and cell kills itself
3. Preventing tumour growth
How does surgery help treat cancer? 3 mark
1. Remove part of the tumour
2. Activates the cell cycle
3. Making radiation and chemotherapy more effective
What blood does arteries and arterioles transport?
Name three features of the artery and what it does
1. Smooth muscle to contract for vascoconstriction to change blood flow and pressure
2. Elastic tissue to stretch under pressure and recoil to even out the pressure
3. Smooth epithelium to prevent friction to reduce blood clots
What is the role of capillaries?
Name three features of the capillary and what they do
1. Small lumen to slow substances so more time for exchange
2. One cell thick for a short diffusion pathway
3. Large surface area from a large network of capillaries
What blood do veins transport?
Name three features of a vein and what they do
1. Valves prevent the back flow of blood
2. Body muscles contract to maintain blood flow
2. Wide lumen for low pressure
An increasing respiration in the tissues of a mammal affects the oxygen disassociation curve of haemoglobin. Describe and explain how
There is more carbon dioxide so the curve moves to the right
How are single celled organisms adapted for gas exchange? 2 marks
A large surface area to volume ratio and a thin surface so short diffusion pathway
What system do insects use?
In insects, what does abdominal pumping do?
Get oxygen in quicker, so a steeper concentration gradient
How do insects have a large surface area?
Vast network of trachea and trachioles
How do insects have a short diffusion pathway?
The trachea have thin permeable walls
How do insects maintain concentration gradient?
By the spiracles opening and closing
In what two ways do insects prevent water loss?
They have a waterproof waxy cuticle and they close the spiracles
How do fish have a large surface area?
The gill filaments and lamellae are at 90° right angles
How do fish maintain concentration gradient?
The counter current flow where the blood and water move in opposite directions
How do fish have a short diffusion pathway?
Thin epithelium cells
What do plants need for respiration?
What do plants need for photosynthesis?
What gives leaves a large surface area?
How do leaves have a short diffusion pathway?
The stomata opens
How do leaves maintain a concentration gradient?
By respiration, photosynthesis and stomata opening
What three substances need exchanging?
Respiratory gases, urea and heat
What circulatory system do mammals have?
A double circuit where blood passes through the heart twice
What ratio do large mammals have?
Small surface area to volume ratio
How does water move into the roots
Lower water potential in roots that soil due to amino acids and sugars, so water moves in from high to low water potential by osmosis
How does water move across apoplastic pathway?
Moves through nonliving cell wall using cohesion between water molecules until it reaches the casparian strip, where it is forced into the symplastic pathway
How does water move through the symplastic pathway?
Through the living cytoplasm by osmosis from high to low potential through the plasmadesmata
How does water move into the xylem?
Active transport by endodermis of salts into the xylem known as root pressure. Lowers water potential, so moves from high to low water potential into xylem
How does water move up xylem?
Evaporation/transpiration from the leaves
Create cohesion and tension between water molecules by hydrogen bonds
Adhesion/ water molecules bind to xylem
Creating continuous water column
What are the four factors that affect transpiration?
Temperature, light intensity, air movement and humidity
What three ways plants prevent water loss?
Sunken stomata in pits, layer of hairs on epidermis, Waxy waterproof cuticles
In tissue fluid, what is the right hand side of the capillary end called?
In tissue fluid, what is the left hand side of the capillary called?
What photosynthetic pigment is in the thylakoids?
What is an intron?
Amino acids that don't code for proteins and is removed during protein synthesis
What is an exon?
Amino acids that do code for proteins
What is a mutation?
A random change in the base sequence of DNA
Where are genes found?
A locum on a section of DNA
What is a gene?
A section of DNA that code for polypeptides that affects nature and development
Name the two specific organic base pairings
Adenine & Thymine
Cytosine & Guanine
What do the organic bases contain?
How many hydrogen bonds do guanine and cytosine have?
How many hydrogen bonds do adenine and thymine have?
Name three things that can affect genetic diversity
Genetic bottlenecks, founder effect and selective breeding
What does a decrease in diversity lead to?
Reduction in the variety of alleles
Name two advantages of selective breeding
Produce a higher yield of animals and plants
Produce organisms that are resistant to disease and have a high tolerance to bad conditions
Give two disadvantages of selective breeding
The welfare of the animals is at risk
Reduces genetic diversity so more risk of genetic diseases
What structure is DNA?
Why can't antibiotics be used for viruses?
Viruses don't have a cell wall
What is osmotic lysis?
The cell wall is not formed, so there is a lower water potential in the bacteria, so water enters by osmosis to expand the cell and burst
What three ways can we prevent the occurrence of antibiotic resistance?
Make sure antibiotics prescribed when necessary
Make sure all courses of antibiotics are finished
Ensure hygiene by using antiseptic gel
What are three advantages of using antibiotics that are ethical reasons?
Everybody has the right to medication
Improves quality of life
Give three disadvantages that are ethical reasons of using antibiotics
Should be only saved for life threatening diseases
Shouldn't treat the terminally ill
Increases antibiotic resistance
Give two reasons why it is difficult to define species
Some species are extinct so there is no fossil record
There is lots of variation within species such as different breeds of dogs
Describe DNA hybridisation
1. DNA from two species heated
2. To separate single strands
3. Strands mixed together
4. Strands join by complimentary base pairings
5. Forming hydrogen bonds
6. The more bonds that hybridise, the more similar the DNA is
7. Heat again
8. The higher the temperature needed, the more energy needed to break the bonds
9. The more bonds, they more similar the DNA so the more closely related species are