Higher Biology

1. Higher Biology Revision Exercise Unit 2 Genetics and Adaptation

2. Meiosis/Crosses/Mutation 1. _______ reproduction is the means by which _______ variation is maintained in a population. Sexual genetic 2. _______ is the process by which haploid ________ are formed. Meiosis gametes 3. During meiosis, new combinations of existing _______ arise by ___________ assortment of chromosomes and _________ over between homologous chromosomes. alleles independent crossing 4. If an F2 generation with a phenotype ratio of 9 : 3 : 3 : 1 is obtained as a result of a dihybrid cross where the F1 is selfed, the two genes involved must be located on _________chromosomes. However when the expected ratio of 9 : 3 : 3 : 1 is not obtained, this indicates that the two genes are located on the same chromosome (i.e.are ________. different linked

3. 5. If an F2 generation with a ratio of 1 : 1 : 1 : 1 is obtained as a result of a dihybrid cross where the F1 is ____________ (testcrossed) to the double recessive, the two genes must be located on different chromosomes. However when the expected ratio of 1 : 1 : 1 : 1 is not obtained, this also indicates that the two genes are located on the ______ chromosome (i.e. are linked). backcrossed same 6. Linked genes become __________ if crossing over occurs between them. This produces ____________ gametes. separated recombinant 7. Since the distance between two linked genes is directly related to the __________ of recombination between them, _____________ values can be used to construct gene _____ of chromosomes. frequency recombination maps

4. 8. Genes present on an X but not on a Y chromosome are __________. sex-linked 9. __________ are alterations in genotype which involve a change in structure or ________ of chromosomes or ______ type or sequence of a gene’s DNA. Mutations number base 10. Mutations occur ______ and at random. Their frequency can be increased artificially by ___________ agents, e.g. mustard gas, gamma rays, X-rays and UV light. rarely mutagenic 11. Mutations are the only source of new _________ and provide the raw materials for _________. variation evolution

5. Evolution 1. Natural ________ favours those members of a population best ______ to an environment. selection suited 2. Rare mutant forms sometimes enjoy a selective __________ if some biotic or abiotic factor brings about a change in the ___________ making it favour their survival at the expense of their competitors. advantage environment 3. The rapid appearance of bacteria resistant to __________ is an example of high-speed _________. antibiotics evolution 4. The frequency of occurrence of a gene in a large population mating at random remains constant unless the gene ______ to which it belongs is affected by ________, natural selection, gene __________ or genetic drift. pool mutation migration

6. 5. The members of a _______ form a natural interbreeding group which is reproductively isolated from other species. species 6. The process of speciation depends on ________ to gene exchange dividing a population into two or more ________ groups, each of which takes its own course of evolution. barriers isolated 7. _________ radiation is the _________ over a very long period of time of a group of related organisms along several lines by each becoming adapted to suit a particular ecological ______. Adaptive evolution niche 8. Evolution is a __________ process. As new species appear, other less successful ones become _______. continuous extinct

7. 9. Important wild varieties of crop plant and endangered species are often conserved in cell ______ and _____ breed farms. banks rare 10. Breeders use _________ selection to selectively breed organisms useful to mankind. Loss of genetic _________ is associated with __________ of domestic plants and animals. artificial diversity inbreeding 11. The use of _____________ in plant and animal breeding often produces offspring which show hybrid _______. hybridisation vigour 12. Genes can be located using gene _______ or by recognising _______ patterns on chromosomes. probes banding

8. 13. Using genetic ___________, scientists are able to take genetic material from one species and seal it into the ________ of another species producing an organism which would never have arisen otherwise. engineering genome 14. Sexual ______________ between two species of plant can be overcome by using ________ fusion. incompatibility somatic

9. Maintaining Water Balance 1. Freshwater bony fish constantly _____ water by osmosis from the surrounding _________ water. gain hypotonic 2. Their kidneys possess many ______ glomeruli which allow a ______ filtration rate of blood resulting in the loss of much water in urine. large rapid 3. Their ________ secretory cells actively _______ salts from external water. chloride absorb 4. Saltwater bony fish constantly _____ water by osmosis to the surrounding __________ water. lose hypertonic 5. They drink sea water and have kidneys with few ______ glomeruli which allow only a ______ water to be lost in urine. small little

10. 6. Their chloride _________ cells actively _______ excess salt out into the sea secretory excrete 7. Migratory fish are adapted to cope with changes in ______ concentration of the external environment by altering their method of ______________ as required. water osmoregulation 8. Desert mammals show ___________ and ____________ adaptations which enable them to ________ water. behavioural physiological conserve 9. The continuous passage of water and nutrient ions up through a plant is called the transpiration _______. It is the means by which cells are supplied with _____ and water needed for biochemical reactions. stream ions 10. The force with which water is pushed up a stem by the roots is called root ________. pressure

11. 11. ____________ is the loss of water by evaporation. It occurs mainly through _______ in leaves. Transpiration stomata 12. This loss of water sets up a transpiration ____ which draws columns of water molecules up through the xylem vessels. This is explained in terms of the _______________ theory. pull cohesion-tension 13. Changes in ______ of guard cells bring about opening and closing of stomata. turgor 14. Transpiration rate is affected by several different ______________ factors. environmental 15. __________ are plants adapted to survive in dry or _______ habitats. Xerophytes exposed 16. ___________ are plants adapted to survive completely or partially __________ in water. Hydrophytes submerged

12. Obtaining Food 1. Many animals show distinct behaviour patterns when ________ for food. foraging 2. Such behaviour tends to increase the animal’s chance of gaining maximum net ______. energy 3. To be economical an animal must forage _________ with respect to search and pursuit _____, type of food selected and _______ of food selected. optimally time energy 4. ___________ competition occurs between members of the same species; ___________ competition occurs between members of different species. Intraspecific interspecific

13. 5. Intraspecific competition for territories is called ____________. It spaces out a population in relation to available _____ supply. territoriality food 6. Dominance _________ amongst the members of a social group involves lower ranking individuals acknowledging the status of those with higher _____. They do this by showing ___________ responses to the latter’s threat displays. This behaviour conserves energy and ensures experienced __________. hierarchy rank subordinate leadership 7. ____________ hunting benefits all the members of a _____ group since all the animals gain more food than they would hunting on their own. Co-operative social 8. Animals are mobile but plants are ______ . This normally poses no problem for plants since their immediate environment provides all the raw _________ needed for survival. sessile materials

14. 9. Intraspecific competition exists amongst the members of a dense population of plants for _____, water and soil _________. light nutrients 10. Interspecific competition between plants tends to be less _______ than intraspecific competition because different species often have different ____________. intense requirements 11. Moderate grazing of grassland by rabbits maintains species ________ since dominant plants are held in ______. diversity check 12. Compensation point is that low level of light ________ at which the rate of photosynthesis in a plant exactly equals the rate of ___________. A shade plant is found to have its ____________ point at a lower intensity of light than a ____ plant. intensity respiration compensation sun

15. Coping With Danger 1. Some animals learn not to react to a stimulus if, after many repeats, it proves to be harmless. This is called ___________. habituation energy 2. Habituation prevents the animal wasting time and _______ on needless repeats of its ______ response. escape 3. Habituation only brings about a __________ modification of the escape response, otherwise the animal would be left open to _______. short-term danger 4. In advanced animals, learning involves a _________ modification of the response made to a stimulus. Information is stored in the central nervous system and ____________for future use. long-term remembered

16. 5. Animals show many __________ defence mechanisms such as ___________ and protective coverings. individual camouflage 6. _______ mechanisms for defence are found amongst animals which remain together in a protective _______. Social group 7. Some plants possess __________ adaptations for defence such as thorns and _______. structural spines 8. The ________ form of some plants enables them to tolerate _________ animals. growth grazing the end