Reproductive isolation

Question 1

how does reproductive isolation cause allopatric speciation

Answer 1

1. two populations become reproductively isolated by a geographically feature so there is no flow of genes or allele between them
2. over time they are exposed to different selection pressures in their environments
3. within each population, organisms with alleles that result in adaptations suited to their particular environment are more likely to survive, reproduce and pass the alleles on.
4. over time the allele frequencies of each population will change in different ways leading to different phenotypes being common in each population
5. eventually individuals from the different populations will have changed so much they wont be able to breed with one another to produce fertile offspring

Question 2

how does reproductive isolation lead to sympratic speciation

Answer 2

two populations become reproductively isolated without there being a geographical barrier but there is no flow of gene or alleles between them - for example at different times of the year
-same process as before