[18.5] isolation and speciation

Question 1

what is speciation?

Answer 1

the formation of new species from pre-existing species over time as a result of changes to gene pools from generation to generation

Question 2

what can cause speciation?

Answer 2

genetic isolation between the new population and the pre-existing species population

Question 3

how can you determine speciation has occurred?

Answer 3

when two populations can no longer interbreed successfully to produce fertile offspring

Question 4

what are 2 forms of speciation?

Answer 4

• allopatric speciation
• sympatric speciation

Question 5

what is allopatric speciation?

Answer 5

two populations of a species are separated by a geographical barrier and become genetically isolated from each other

Question 6

what is sympatric speciation?

Answer 6

two populations of species are living in the same area, experiencing similar environmental selection pressures but still become genetically isolated from each other

Question 7

what does genetic isolation mean?

Answer 7

individuals within the two separate populations can no longer freely interbreed

Question 8

what is genetic drift?

Answer 8

when the change in allele frequencies in the population is due to random chance, rather than environmental selective pressures

Question 9

speciation scaffold

Answer 9

1. reproductive isolation so no interbreeding between populations
2. variations due to mutations occurring separately in the different populations
3. different selective pressures acting on the different populations
4. differential reproductive success in the populations
5. leads of different changes in allele frequency in each population
6. eventually, members of the two populations become so different they are unable to reproduce to produce fertile offspring

Question 10

what different isolating mechanisms are there? (7)

Answer 10

• geographical
• ecological
• temporal
• behavioural
• mechanical
• gametic
• hybrid sterility