Understanding:
• Reproductive isolation of populations can be temporal, behavioural or geographic
Reproductive isolation occurs when barriers prevent two populations from interbreeding – keeping their gene pools separate
There are two main categories of reproductive isolation barriers:
- Prezygotic isolation – occurs before fertilisation can occur (no offspring are produced)
- Postzygotic isolation – occurs after fertilisation (offspring are either not viable or infertile)
Prezygotic isolation barriers can be temporal, behavioural, geographic / ecological or mechanical; whereas postzygotic isolation barriers include the inviability, infertility or breakdown of hybrid organisms
Reproductive Isolation Mechanisms
Temporal Isolation
- Temporal isolation occurs when two populations differ in their periods of activity or reproductive cycles
- Example: Leopard frogs and wood frogs reach sexual maturity at different times in the spring and hence cannot interbreed
Behavioural Isolation
- Behavioural isolation occurs when two populations exhibit different specific courtship patterns
- Example: Certain populations of crickets may be morphologically identical but only respond to specific mating songs
Geographic Isolation
- Geographic isolation occurs when two populations occupy different habitats or separate niches within a common region
- Example: Lions and tigers occupy different habitats and do not interbreed (usually)
Types of Reproductive Isolation
