7.3.6 Reproductive Separation

Key Stages of Reproductive Separation

1. Isolation of Populations:

• A population is split into separate groups by geographical, behavioural, or temporal barriers.
• Examples:
• Geographical isolation (e.g., mountains or rivers separate populations).
• Behavioural isolation (e.g., differences in courtship behaviours).
• Temporal isolation (e.g., species reproduce at different times).

2. Accumulation of Genetic Differences:

• Once isolated, populations experience different mutations and undergo natural selection based on their unique environments.
• Genetic drift may also play a role, especially in small populations.

3. Formation of a New Species:

• Over time, the genetic differences become so significant that the populations can no longer interbreed to produce fertile offspring.
• This is known as speciation.

Types of Speciation

1. Allopatric Speciation:

• Occurs due to geographical isolation.
• Example: Darwin's finches on the Galápagos Islands evolved into different species due to isolation on separate islands.

2. Sympatric Speciation:

• Occurs without geographical barriers.
• Often results from behavioural or reproductive isolation within the same habitat.
• Example: Different mating preferences within the same population.