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Higher Biology Revision Exercise Unit 2 Genetics and Adaptation Meiosis/Crosses/Mutation 1. _______ Sexual reproduction is the means by which _______ genetic variation is maintained in a population. 2. Meiosis _______ is the process by which haploid ________ gametes are formed. 3. During meiosis, new combinations of existing _______ alleles arise by ___________ independent assortment of chromosomes and _________ crossing over between homologous chromosomes. 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. different 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 ________. linked 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 ____________ backcrossed (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 same chromosome also indicates that the two genes are located on the ______ (i.e. are linked). 6. Linked genes become __________ separated if crossing over occurs between them. This produces ____________ recombinant gametes. 7. Since the distance between two linked genes is directly related to the __________ frequency of recombination between them, _____________ recombination values can be used to construct gene _____ maps of chromosomes. 8. Genes present on an X but not on a Y chromosome are __________. sex-linked 9. Mutations __________ are alterations in genotype which involve a change in structure or ________ number of chromosomes or ______ base type or sequence of a gene’s DNA. 10. Mutations occur ______ rarely and at random. Their frequency can be increased artificially by ___________ mutagenic agents, e.g. mustard gas, gamma rays, X-rays and UV light. 11. Mutations are the only source of new _________ variation and provide the raw materials for _________. evolution Evolution 1. Natural ________ selection favours those members of a population best ______ suited to an environment. 2. Rare mutant forms sometimes enjoy a selective __________ advantage if some biotic or abiotic factor brings about a change in the ___________ environment making it favour their survival at the expense of their competitors. 3. The rapid appearance of bacteria resistant to __________ antibiotics is an example of high-speed _________. evolution 4. The frequency of occurrence of a gene in a large population mating at random remains constant unless the gene ______ pool to which it belongs is affected by ________, mutation natural selection, gene __________ migration or genetic drift. 5. The members of a _______ species form a natural interbreeding group which is reproductively isolated from other species. 6. The process of speciation depends on ________ barriers to gene exchange dividing a population into two or more ________ isolated groups, each of which takes its own course of evolution. 7. _________ Adaptive radiation is the _________ evolution 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 ______. niche 8. Evolution is a __________ continuous process. As new species appear, other less successful ones become _______. extinct 9. Important wild varieties of crop plant and endangered species are often conserved in cell ______ banks and _____ rare breed farms. 10. Breeders use _________ artificial selection to selectively breed organisms useful to mankind. Loss of genetic _________ diversity is associated with __________ inbreeding of domestic plants and animals. 11. The use of _____________ hybridisation in plant and animal breeding often produces offspring which show hybrid _______. vigour 12. Genes can be located using gene _______ probes or by recognising _______ banding patterns on chromosomes. 13. Using genetic ___________, engineering scientists are able to take genetic material from one species and seal it into the ________ genome of another species producing an organism which would never have arisen otherwise. 14. Sexual ______________ incompatibility between two species of plant can be overcome by using ________ somatic fusion. Maintaining Water Balance 1. Freshwater bony fish constantly _____ gain water by osmosis from the surrounding _________ hypotonic water. 2. Their kidneys possess many ______ large glomeruli which allow a ______ rapid filtration rate of blood resulting in the loss of much water in urine. 3. Their ________ chloride secretory cells actively _______ absorb salts from external water. 4. Saltwater bony fish constantly _____ lose water by osmosis to the surrounding __________ hypertonic water. 5. They drink sea water and have kidneys with few ______ small glomeruli which allow only a ______ little water to be lost in urine. 6. Their chloride _________ secretory cells actively _______ excrete excess salt out into the sea 7. Migratory fish are adapted to cope with changes in ______ water concentration of the external environment by altering their method of ______________ osmoregulation as required. 8. Desert mammals show ___________ behavioural and ____________ physiological adaptations which enable them to ________ conserve water. 9. The continuous passage of water and nutrient ions up through a plant is called the transpiration _______. stream It is the means by which cells are supplied with _____ ions and water needed for biochemical reactions. 10. The force with which water is pushed up a stem by the roots is called root ________. pressure 11. ____________ Transpiration is the loss of water by evaporation. It occurs mainly through _______ stomata in leaves. 12. This loss of water sets up a transpiration ____ pull which draws columns of water molecules up through the xylem vessels. This is explained in terms of the _______________ cohesion-tension theory. 13. Changes in ______ turgor of guard cells bring about opening and closing of stomata. 14. Transpiration rate is affected by several different ______________ environmental factors. 15. Xerophytes __________ are plants adapted to survive in dry or exposed _______ habitats. 16. Hydrophytes ___________ are plants adapted to survive completely or partially __________ submerged in water. Obtaining Food 1. Many animals show distinct behaviour patterns when ________ foraging for food. 2. Such behaviour tends to increase the animal’s chance of gaining maximum net energy ______. 3. To be economical an animal must forage _________ optimally with respect to search and pursuit _____, time type of food selected and _______ energy of food selected. 4. Intraspecific ___________ competition occurs between members of the same species; ___________ interspecific competition occurs between members of different species. 5. Intraspecific competition for territories is called ____________. territoriality It spaces out a population in relation to available _____ food supply. 6. Dominance _________ hierarchy amongst the members of a social group involves lower ranking individuals acknowledging the status of those with higher _____. rank They do this by showing ___________ subordinate responses to the latter’s threat displays. This behaviour conserves energy and ensures leadership experienced __________. 7. Co-operative ____________ hunting benefits all the members of a _____ social group since all the animals gain more food than they would hunting on their own. 8. Animals are mobile but plants are ______ sessile . This normally poses no problem for plants since their immediate environment provides all the raw _________ materials needed for survival. 9. Intraspecific competition exists amongst the members of a dense population of plants for _____, light water and soil _________. nutrients 10. Interspecific competition between plants tends to be less _______ intense than intraspecific competition because different species often have different ____________. requirements 11. Moderate grazing of grassland by rabbits maintains species ________ since dominant plants are held in ______. check diversity 12. Compensation point is that low level of light ________ intensity at which the rate of photosynthesis in a plant exactly equals the rate of ___________. respiration A shade plant is found to have its ____________ compensation point at a lower intensity of light than a ____ sun plant. 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 on 2. Habituation prevents the animal wasting time and _______ escape response. needless repeats of its ______ 3. Habituation only brings about a __________ short-term modification of the danger escape response, otherwise the animal would be left open to _______. 4. In advanced animals, learning involves a _________ long-term modification of the response made to a stimulus. Information is stored in the central remembered nervous system and ____________for future use. 5. Animals show many __________ individual defence mechanisms such as camouflage ___________ and protective coverings. 6. _______ Social mechanisms for defence are found amongst animals which group remain together in a protective _______. 7. Some plants possess __________ structural adaptations for defence such as spines thorns and _______. 8. The ________ growth form of some plants enables them to tolerate grazing animals. _________ the end