7.3.7 Types of Speciation

Key Types of Speciation

1. Allopatric Speciation:

• Occurs due to geographical isolation (e.g., mountains, rivers, or continental drift).
• Gene flow between separated populations is reduced or stopped.
• Each population experiences different selection pressures (e.g., climate, predators, food sources).
• Over time, the populations accumulate genetic differences through mutation, natural selection, and genetic drift.
• Eventually, they become so genetically distinct that they cannot interbreed to produce fertile offspring.
• Example:
• The camel and llama share a common ancestor but evolved separately after Africa and South America were divided by continental drift.

2. Sympatric Speciation:

• Occurs within the same geographical area (no physical barriers).
• Caused by reproductive isolation due to factors such as:
• Mutations: Chromosomal changes, such as polyploidy in plants, can result in individuals being unable to breed with the original population.
• Behavioural isolation: Changes in courtship behaviour may prevent recognition between individuals.
• Anatomical isolation: Structural differences, e.g., incompatibility of reproductive organs, can prevent successful mating.
• Example:
• Cichlid fish in African lakes developed different feeding preferences and mating behaviours, leading to the evolution of new species without geographical barriers.