Evolution may lead to speciation (18)

Question 1

What are 3 genetic factors that can cause phenotypic variation?

Answer 1

1) mutation of alleles
2) random fertilisation
3) random assortment of genetic material during meiosis

Question 2

What factor, other than genetic factors, can also cause phenotypic variation?

Answer 2

environmental influences

Question 3

What are 3 reasons for natural selection?

Answer 3

1) predation
2) disease
3) competition

Question 4

How does natural selection cause a gene pool to change overtime?

Answer 4

organisms with advantageous characteristics are more likely to survive and pass favourable alleles to offspring so frequency of unfavourable alleles decreases

Question 5

What is meant by speciation?

Answer 5

where a population is split and isolated and different selective pressures are placed on the groups so that the genetic make up changes to the extent that the 2 groups can no longer interbreed, causing them to become 2 separate species

Question 6

What are the 2 types of speciation?

Answer 6

allopatric speciation
sympatric speciation

Question 7

What is meant by allopatric speciation?

Answer 7

caused by a physical barrier (e.g. river, mountain range) so the environments occupied by the 2 groups are different and therefore different alleles are favoured

Question 8

What is meant by sympatric speciation?

Answer 8

caused by a non-physical barrier (e.g. mutation no longer allowing 2 organisms to produce fertile offspring) so any changes in anatomy or behaviour may also prevent breeding

Question 9

Why does genetic drift affect small populations more than large populations?

Answer 9

gene pool is smaller so there are less alleles available so any changes in frequency become pronounced very quickly

Question 10

What is meant by genetic drift?

Answer 10

change in populations allele frequency that occurs due to chance rather than selective pressures (basically caused by a ‘sampling error’ during reproduction)

Question 11

What are the 3 types of selection?

Answer 11

stabilising
directional
disruptive

Question 12

What is stabilising selection?

Answer 12

when individuals closest to the mean are favoured so any new characteristics are selected against

Question 13

What does stabilising selection cause?

Answer 13

low diversity

Question 14

When does stabilising selection occur?

Answer 14

when environmental conditions stay the same

Question 15

When does directional selection occur?

Answer 15

when environmental conditions change

Question 16

What does directional selection cause?

Answer 16

overtime the mean of the population will move towards the more favourable characteristics for the new environment

Question 16

What is directional selection?

Answer 16

individuals with phenotypes suited to the new conditions will survive and pass on their genes

Question 17

What is disruptive selection?

Answer 17

opposite of stabilising as both extremes of the normal distribution are favoured over the mean

Question 18

What does disruptive selection cause?

Answer 18

overtime population becomes phenotypically divided

Question 19

What 3 factors cause genetic variation?

Answer 19

1) random fertilisation
2) crossing over
3) independent segregation