Term
| Briefly describe the events in mitotic prophase. |
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Definition
| Chromosomes become visible. The nuclear envelope breaks down. Spindle fibres form a spindle. |
|
|
Term
| Briefly describe the events in mitotic telophase. |
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Definition
| Daughter chromosomes reach the poles. The spindle breaks down, the nuclear envelope reforms and two distinct nuclei are formed. |
|
|
Term
| By what process do bacteria divide? |
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Definition
|
|
Term
| By what two routes can tissue fluid return to the circulatory system? |
|
Definition
| Via the lymphatic system (through lymph vessels) or reabsorption into the venous end of the capillaries |
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Term
| Describe a piece of evidence that supports the root pressure theory of movement of water through stems and explain how it supports this theory. |
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Definition
| Sap exudes from cut, rooted stem; only upward force could make this happen. |
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Term
| Describe and explain how having large areas of land given over to the production of just one crop reduces biodiversity. |
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Definition
| area dominated by just one species; other organisms controlled by pesticides; hedgerows removed, reducing number of habitats; wetlands drained to create more agricultural land, reducing number of habitats |
|
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Term
| Describe how water leaves plant leaf cells. |
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Definition
| Evaporates from surfaces of spongy mesophyll cells to air spaces and diffuses down a water vapour concentration gradient from air spaces into atmosphere through stomata |
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Term
| Describe the layers of structure of arteries, arterioles and veins from outside to inside. |
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Definition
| Tough outer layer that resists pressure; muscle layer that contracts to control blood flow; elastic layer to maintain blood pressure/smooth out blood flow; endothelium which prevents friction and is thin; lumen, the central cavity through which blood flows |
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Term
| Describe two adaptations of fish gills for efficient gas exchange. |
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Definition
| Made of long, thin filaments; gill lamellae on the surface of the filaments; both increase the surface area of the gills. |
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|
Term
| Explain how a genetic bottleneck reduces genetic diversity. |
|
Definition
| Drop in populations due to chance event; few surviving indiviuals have fewer, less diverse alleles; as individuals breed/population grows alleles are equally less diverse; reduced genetic diversity. |
|
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Term
| Explain how evaporation from the leaves can cause water to move upwards through the stem. |
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Definition
| Water potential in the mesophyll cells of the leaf decreases, so water moves from the xylem into the leaves by osmosis. This creates a pull/tension on the water in the xylem due to cohesion between water molecules. |
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Term
| Explain how overuse of antibiotics results in antibiotic-resistant strains of bacteria. |
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Definition
| Mutation occurs giving a bacterium a resistance allele; resistant bacteria survive and reproduce, passing on the allele by vertical or horizontal gene transmission |
|
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Term
| Explain how root pressure results in the movement of water through the xylem. |
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Definition
| Active transport of mineral ions lowers the water potential of xylem, establishing a WP gradient; water moves by osmosis through the partially permeable membrane of the endodermal cells into the xylem; the volume of water in the xylem increases and cannot move back due to the water potential gradient, so the pressure increases and forces the water a few cm up the xylem. |
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Term
| Explain how the features of starch enable it to act as a storage substance. |
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Definition
| Coiled/helical, so tightly packed; insoluble, so exerts no osmotic effect; long chain, so contains many glucose units; branched chains, so easy to remove glucose |
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Term
| Explain why scientists can use protein structures to investigate the evolutionary relationships between different species. |
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Definition
| Compare amino acid sequences; closer amino acid sequence = closer relationship, as protein structure is related to DNA base sequence |
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Term
| Explain why the presence of carbon dioxide leads to the Bohr effect. |
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Definition
| Carbon dioxide reacts with water to form carbonic acid, lowering the pH of the blood; Hb acts as a buffer to maintain the right pH; the change in shape of Hb lowers its affinity for oxygen. |
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Term
| Give differences in the arrangement of DNA in a eukaryotic and prokaryotic cell. |
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Definition
| Eukaryotes: linear, associated with histones too form chromosomes, found in nucleus; prokaryotes: circular, not associated with histones, some exists as plasmids, free in cytoplasm |
|
|
Term
| Give four ways in which genetic variation is brought about. |
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Definition
| Mutations (producing new alleles); genetic crossover in meiosis; independent segregation of chromosomes in meiosis; random fertilisation of gametes (the final three giving rise to new combinations of existing alleles) |
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Term
| Give two reasons why meiosis leads to genetic variation. |
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Definition
| 1. Independent assortment: the chromosomes in the daughter cell will be a random mixture of paternal and maternal chromosomes 2. Genetic crossover leads to further variation |
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|
Term
| How can DNA hybridisation be used to determine the evolutionary relationships between species? |
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Definition
| The closer the evolutionary relationship, the more complementary base pairs there will be, so the more hydrogen bonds form and thus the higher the temperature needed to separate the strands. |
|
|
Term
| How does courtship result in successful mating? |
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Definition
| Individual attracts/recognises mate of the same species; indication of fertility to synchronise mating; stimulates release of gametes. |
|
|
Term
| How does water move through the apoplast pathway? |
|
Definition
| Cohesion between water molecules |
|
|
Term
| How does water move through the symplast pathway? |
|
Definition
|
|
Term
| How is oxygen taken into fish? |
|
Definition
| Water is taken in through the mouth and flows over the gills; oxygen diffuses from water into the blood. |
|
|
Term
| How is tissue fluid moved through lymph vessels? |
|
Definition
| Hydrostatic pressure and contraction of body muscles that squeeze the lymph vessels towards the heart |
|
|
Term
| How many oxygen molecules can be carried by one Hb molecule? Why? |
|
Definition
| 4; each Hb molecule has four haem groups (one on each subunit) |
|
|
Term
| In a potometer, how is the air bubbled returned to the start of the capillary tube? |
|
Definition
| Tap opened/water added from reservoir |
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|
Term
| Mice have a higher rate of metabolism than humans due to their large surface area to volume ratio. Suggest why the oxygen dissociation curve in mice is shifted to the right relative to that in humans. |
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Definition
| Oxygen needs to be unloaded more easily to respiring tissues to support the increased rate in metabolism. Haemoglobin is still saturated at atmospheric pressures so there is no disadvantage in loading oxygen. |
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|
Term
| Name the genus and species to which Mycobacterium bovis belongs. |
|
Definition
| Genus: Mycobacterium Species: bovis |
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|
Term
| Name the seven taxonomic groups in order. |
|
Definition
| Kingdom, Phylum, Class, Order, Family, Genus, Species |
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|
Term
| Other than large areas of land being given over to the production of just one crop, describe and explain two ways in which agricultural practices reduce biodiversity. |
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Definition
| => Widespread use of fertilisers; causes eutrophication, damaging aquatic ecosystems as waterways become anoxic. => Hunting or culling of species because of their impact on livestock (e.g. foxes) |
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Term
| Suggest whether the oxygen dissociation curve of haemoglobin in an organism living at high altitudes would be shifted to the left or the right relative to that of human haemoglobin. |
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Definition
| To the left; pp of oxygen is lower, so it must be loaded more easily by haemoglobin |
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|
Term
| Suggest why identical twins may differ at birth. |
|
Definition
| Different positions in the womb; different sized placentas; received different amounts of nutrients and hormones |
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Term
|
Definition
| Replicated chromosomes before segregation |
|
|
Term
| What are each of a pair of replicate chromosomes called before segregation? |
|
Definition
|
|
Term
| What are homologous chromosomes? |
|
Definition
| Chromosomes having the same genes at the same loci |
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|
Term
|
Definition
| Narrow membrane-lined channels through the cell wall which connect adjacent plant cells |
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|
Term
| What are some of the ethical issues associated with the selective breeding of domesticated animals? |
|
Definition
| Selective breeding is interfering with nature; balance of increased yield with animal welfare; reduced genetic diversity - loss of alleles that could be of benefit in the future; exploitation of domestic animals for human gain |
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|
Term
| What are stacks of thylakoids in plant chloroplasts called? |
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Definition
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|
Term
| What are the economic arguments in favour of conserving biodiversity? |
|
Definition
| Medical/pharmaceutical uses; commercial products; tourism; agriculture |
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|
Term
| What are the ethical arguments in favour of conserving biodiversity? |
|
Definition
| Preventing extinction/loss of populations/reduction of populations/loss of habitats/save organisms for future generations |
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|
Term
| What are the four subphases of mitosis (in order)? |
|
Definition
| Prophase, metaphase, anaphase, telophase |
|
|
Term
| What are the names of the pores in insects through which air enters the tracheae? |
|
Definition
|
|
Term
| What are the three components of a DNA nucleotide? |
|
Definition
| A sugar (deoxyribose), a phosphate group and a nitrogenous base (A, C, G or T) |
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|
Term
| What can be said about an ecosystem with a high biodiversity index? |
|
Definition
| A number of successful species; stable ecosystem; environment not hostile; complex food web; environmental change will be less damaging to the whole ecosystem |
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|
Term
| What can be said about an ecosystem with a low biodiversity index? |
|
Definition
| Dominated by a few species; hostile environment; unstable ecoystem - change in environment would have serious effects; simple food chains |
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|
Term
| What forces tissue fluid out of the capillaries into tissues? |
|
Definition
| Hydrostatic pressure in the capillaries |
|
|
Term
| What happens in anaphase of mitosis? |
|
Definition
| Chromatids separate and begin to move towards opposite poles. |
|
|
Term
| What happens in metaphase of mitosis? |
|
Definition
| The chromosomes line up at the equatorial plate. Each chromatid is connected to one of the poles by microtubules. |
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|
Term
| What happens in mitotic anaphase that results in the production of two genetically identical cells? |
|
Definition
| Identical sister chromatids move to opposite poles of the spindle |
|
|
Term
| What happens inside the cell during the G1 phase? |
|
Definition
| The cell grows and new organelles are synthesised in preparation for mitosis |
|
|
Term
| What is a genetic bottleneck? |
|
Definition
| A dramatic drop in a population, e.g. due to a catastophic event such as a volcanic eruption, which causes the gene pool to plummet - surviving individuals breed but there is a much smaller variety of alleles |
|
|
Term
|
Definition
| The total number of organisms of one species in a given area at a given time |
|
|
Term
|
Definition
| A group of individuals that are similar physically and physiologically and which can interbreed to produce fertile offspring. |
|
|
Term
|
Definition
| One of two or more versions of a gene, e.g. blue or brown alleles of the gene for eye colour |
|
|
Term
|
Definition
| A combination of different types of tissue that are coordinated to perform a function or variety of functions. |
|
|
Term
| What is DNA hybridisation? |
|
Definition
| DNA from two species is unwound and put together in solution; hybridised DNA (with one strand from each species) is heated until the strands separate. |
|
|
Term
| What is meant by adhesion as applied to water molecules? |
|
Definition
| Water molecules stick to other substances (e.g. plant stems) |
|
|
Term
| What is meant by cohesion as applied to water molecules? |
|
Definition
| Water molecules stick well to each other (hydrogen bonding) |
|
|
Term
| What is meant by countercurrent flow in fish, and how does it increase the efficiency of gas exchange? |
|
Definition
| Blood and water flow in opposite directions; since water and blood are constantly being replaced, the concentration gradient is maintained. |
|
|
Term
| What is meant by discontinuous variation? |
|
Definition
| Variation in which only a limited number of discrete (separate) categories are possible, for example, human ABO blood groups |
|
|
Term
| What is meant by genetic diversity? |
|
Definition
| The variety of alleles within a population |
|
|
Term
| What is meant by interspecific variation? |
|
Definition
| Variation between different species |
|
|
Term
| What is meant by intraspecific variation? |
|
Definition
| Variation within a species |
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|
Term
| What is meant by the founder effect and how does it reduce genetic diversity? |
|
Definition
| When a few individuals from a population colonise a new region, carrying only a small fraction of the alleles; the individuals breed but there is a large decrease in genetic diversity due to the small gene pool |
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|
Term
| What is meant by the term ecological niche? |
|
Definition
| The status of an organism within its environment and community (affecting its survival as a species) |
|
|
Term
| What is meant by ultrafiltration in the context of tissue fluid and its formation? |
|
Definition
| The overall pressure that pushes tissue fluid out of the capillaries is only enough to force out small molecules and leaves behind cells and proteins |
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|
Term
| What is the advantage of the Bohr effect for organisms? |
|
Definition
| Heavily respiring tissues produce more carbon dioxide, so oxygen is released more readily to tissues that need it most; at the gas exchange surface carbon dioxide is constantly removed, so more oxygen can be loaded. |
|
|
Term
| What is the blood vessel that goes from the intestines to the liver, and what does the blood in it contain? |
|
Definition
| Hepatic portal vein; blood contains soluble food molecules, water and mineral ions |
|
|
Term
|
Definition
| The shift of the oxygen dissociation curve to the right due to the presence of carbon dioxide |
|
|
Term
|
Definition
| The region where two chromatids are connected |
|
|
Term
| What is the fundamental difference between anaphase I of meiosis and anaphase of mitosis? |
|
Definition
| Sister chromatids do not separate in anaphase I of meiosis |
|
|
Term
| What is the name of the blood vessel that supplies the kidneys with blood, and what does the blood in it contain? |
|
Definition
| Renal artery; lots of urea and uncontrolled amounts of water and mineral ions |
|
|
Term
| What is the name of the blood vessel which goes from the liver back to the heart, and what does the blood in it contain? |
|
Definition
| Hepatic vein; blood contains urea and controlled amounts of glucose and amino acids |
|
|
Term
| What is the name of the enzyme that polymerises nucleotides during DNA replication? |
|
Definition
|
|
Term
| What is the name of the enzyme which unwinds the double helix and separates DNA strands during replication? |
|
Definition
|
|
Term
| What is the name of the fluid inside plant chloroplasts? |
|
Definition
|
|
Term
| What is the name of the pressure caused by the flow of blood from the arterioles into the capillaries? |
|
Definition
|
|
Term
| What is the name of the process that gives rise to horizontal gene transmission? Describe the events that take place. |
|
Definition
| Conjugation; one cell produces a thin projection that meets another cell, forming a conjugation tube; plasmid is replicated and passed in a linear strand from donor to recipient; plasmid reforms in recipient cell |
|
|
Term
| What is the name of the region where two chromatids are connected? |
|
Definition
|
|
Term
| What is the name of the structure formed during mitosis from fibres which extend from opposite ends of the nucleus? |
|
Definition
|
|
Term
| What is the plural of genus? |
|
Definition
|
|
Term
| What is the purpose of the arteries having a thick muscle layer? |
|
Definition
| Allows arteries to be constricted and dilated in order to control the volume of blood passing through them |
|
|
Term
| What is the purpose of the arterioles having a thicker muscle layer than arteries? |
|
Definition
| Contraction of muscle layer allows constriction of the lumen, controlling movement of blood into the capillaries |
|
|
Term
| What is the purpose of the artery wall having a thick elastic layer? |
|
Definition
| The elastic wall is stretched during the systole and recoils during the diastole to maintain high pressure and smooth blood flow |
|
|
Term
| What is the purpose of the waxy cuticle in plant leaf cells and where is it found? |
|
Definition
| Reduces water loss; on the exterior of the epidermis |
|
|
Term
| What is the role of tissue fluid? |
|
Definition
| To exchange materials between blood and cells |
|
|
Term
| What is tissue fluid made up of? |
|
Definition
| Water, glucose, amino acids, fatty acids, salts and oxygen |
|
|
Term
| What monomer makes up DNA? |
|
Definition
|
|
Term
| What name is given to a chromosome in a prokaryotic cell, owing to the way it is packaged into the cell? |
|
Definition
|
|
Term
| What name is given to an aligned pair of homologous chromosomes during prophase of meiosis I? |
|
Definition
|
|
Term
| What name is given to the compartments in chloroplasts which contain chlorophyll? |
|
Definition
|
|
Term
| What part of haemoglobin binds with oxygen? |
|
Definition
|
|
Term
| What precautions should be taken when setting up a potometer to obtain reliable measurements? |
|
Definition
| Shoots cut/apparatus assembled underwater; leaves left to dry/dried with paper towel; waterproof jelly used to seal joints; ensure no air bubbles present when setting up; shut the tap |
|
|
Term
| What two forces oppose the outward movement of tissue fluid from the capillaries? |
|
Definition
| Hydrostatic pressure from tissue fluid outside the capillaries; osmotic pressure due to plasma proteins in the blood |
|
|
Term
| What type of gene transmission occurs as a result of binary fission? |
|
Definition
| Vertical gene transmission |
|
|
Term
| When measuring variation within a population sample, what two things should be ensured about the sample and why? |
|
Definition
| It should be random to remove bias, and large enough to be representative of the population |
|
|
Term
| When using a potometer, why must the shoots be cut and apparatus assembled underwater? |
|
Definition
| To prevent air from getting into the xylem, forming air locks which would interrupt the transpiration stream/flow of water |
|
|
Term
| Which of the meiotic divisions causes the chromosome number to halve? |
|
Definition
|
|
Term
| Which of the three polysaccharides of glucose is the most branched? |
|
Definition
|
|
Term
| Which of the two meiotic divisions is similar to mitosis? |
|
Definition
|
|
Term
|
Definition
| To maintain a large surface area:volume ration necessary for proper functioning |
|
|
Term
| Why are palisade mesophyll cells packed tightly together? |
|
Definition
| To maximise the amount of light they trap |
|
|
Term
| Why do arterioles have a thinner elastic layer than arteries? |
|
Definition
|
|
Term
| Why does a potometer not truly measure the rate of transpiration? |
|
Definition
| => Measures water uptake, but not all water is lost by transpiration as water is used in photosynthesis, hydrolysis reactions and for support/turgor. => Water is produced in respiration and condensation reactions. => Apparatus may not be sealed/have leaks |
|
|
Term
| Why is an artery classed as an organ? |
|
Definition
| It is made of different types of tissue (e.g. muscle fibre, endothelial) |
|
|
Term
| Why is carbon monoxide poisonous? |
|
Definition
| Hb has a 500x greater affinity for carbon monoxide than for oxygen, so tissues cannot get enough oxygen for respiration. |
|
|
Term
| Why is the diameter of the xylem greater at night? |
|
Definition
| Lower temperatures/stomata closed; less evaporation of water; transpiration stream reduced/water not pulled up the xylem by cohesion; less tension in the xylem, so diameter increases. |
|
|
Term
| Why is there negative pressure in the xylem of plants? |
|
Definition
| Pressure is lower than atmospheric; water is under tension |
|
|
Term
| Why is waterproof jelly used to seal joints when setting up a potometer? |
|
Definition
| To ensure the apparatus is airtight and watertight/prevents air from entering xylem and water from leaking out. |
|
|
Term
| With which base does Adenine pair in DNA? |
|
Definition
|
|
Term
| With which base does cytosine pair? |
|
Definition
|
|
Term
| With which base does guanine pair? |
|
Definition
|
|
Term
| With which base does thymine? |
|
Definition
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