NATURAL SELECTION + SPECIATION

Question 1

What is a gene pool? (1)

Answer 1

the total variety of genes and alleles present in a sexually reproducing population.

Question 2

what is speciation? (1)

Answer 2

the name given to the process by which one species may evolve from another.

Question 3

what are the types of speciation? (2)

Answer 3

-allopatric speciation
-sympatric speciation

Question 4

what is allopatric speciation? (1)

Answer 4

this occurs when two populations are totally separated from each other by a barrier. This prevents interbreeding and mixing of their gene pools.

Question 5

what is sympatric speciation? (1)

Answer 5

this occurs when two populations are still able to mix freely in the same area but some individuals accumulate changes in their gene pools, which are sufficient to prevent interbreeding.

Question 6

what are the types of allopatric speciation? (1)

Answer 6

geographical isolation

Question 7

what is geographical isolation? (2)

Answer 7

geographical isolation occurs when natural, or human-imposed, barriers arise and sharply restrict movement of individuals between the divided populations. It also occurs when motile or mobile species are dispersed to isolated habitats.

Question 8

what are the types of sympatric speciation? (1)

Answer 8

reproductive isolation

Question 9

what is reproductive isolation? (1)

Answer 9

reproductive isolation mechanisms occasionally develop that are strong enough to prevent interbreeding between members of small, isolated populations that have diverged genetically, if only slightly, as a result of their isolation.

Question 10

what are the types of reproductive isolation? (6)

Answer 10

-mismatch of genitalia
-barriers to fertilisation
-formation of sterile hybrids
-behavioural changes
-temporal changes
-ecological changes

Question 11

what is mismatch of genitalia? (1)

Answer 11

this can make successful copulation impossible.

Question 12

what are barriers to fertilisation? (1)

Answer 12

changes in the uterus of animals or the stigma of plants can prevent gametes from meeting

Question 13

what is the formation of sterile hybrids? (1)

Answer 13

When sterile hybrids of two species meet that have different chromosomes, it makes it impossible for the mules chromosomes to form pars in meiosis and therefore produce viable gametes.

Question 14

what are behaviour changes? (1)

Answer 14

many animals have elaborate courtship displays where even small changes will result in rejection by a potential mate.

Question 15

what are temporal changes? (1)

Answer 15

where sure factors such as available food supply cause changes in the timing of gamete production, fertilisation will be prevented.

Question 16

what are ecological changes? (1)

Answer 16

where two populations occupy different parts of the habitat, they are unlikely to meet.

Question 17

what are the different types of selection? (2)

Answer 17

-stabilising selection
-directional selection

Question 18

what is stabilising selection? (1)

Answer 18

this occurs where conditions are favourable and not changing so pressures to change in one way are less than advantage in remaining the same.

Question 19

what is directional selection? (1)

Answer 19

this occurs when environments are changing and there is clear advantage in the population changing in one particular direction