Transcript Document

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
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