Speciation:

Question 1

What is allopatric speciation?

Answer 1

Allopatric speciation occurs when biological populations are physically isolated by an extrinsic barrier and evolve intrinsic reproductive isolation

Question 2

What is sympatric speciation?

Answer 2

Sympatric speciation is when populations of the same species occupy the same habitat but diverge genetically and evolve into distinct species without geographic isolation

Question 3

What is an example of allopatric speciation in marine invertebrates?

Answer 3

Sea mound that wouldn’t usually seperate a population rises above the sea water due to glaciers forming and reducing the sea water -> geographic isolation -> barrier to gene flow -> evolution -> reproductive isolation

Question 4

How could sympatric speciation occur in marine invertebrates?

Answer 4

1. Ecological differentiation - species start to occupy different niches and food resources
2. Habitat preference
3. Reproductive timing
4. Genetic differences accumulate
5. Reproductive isolation occurs
6. New species

Question 5

What is prezygotic isolation?

Answer 5

Reproductive barriers that prevents different species from mating or producing zygotes (fertilised eggs)

Question 6

What are two examples of prezygotic isolation in marine invertebrates?

Answer 6

Gamete incompatibility in sea urchins where the specific bindin protein of one species sperm cannot bind to another species egg. This prevents hybridisation between species.
- timing of gamete release

Question 7

What is postzygotic isolation?

Answer 7

Barriers that occur after zygotic formation that can lead to hybrid inviability, hybrid sterility, and hybrid breakdown.

Question 8

What are two examples of postzygotic isolation in marine invertebrates?

Answer 8

After successful fertilisation and formation of a zygote, the resulting zygotes may not develop properly. This can be seen in sea urchin species where there is high embryonic mortality
- hybrid in viability
- hybrid sterility