Modern Synthetic Theory of Evolution > Isolation

Estimated time: 5 minutes

Maharashtra State Board: Class 12

Key Points: Isolation

Isolation - Separation of a species population into smaller units, preventing interbreeding; barriers that prevent gene flow between isolated populations are called isolating mechanisms; this leads to divergence and speciation.
Geographical Isolation - Physical barriers like rivers, mountains, glaciers divide populations; separated groups acquire new traits by mutations, develop distinct gene pools and eventually form new species; e.g. Darwin's Finches.
Reproductive Isolation - Occurs due to changes in genetic material, gene pool, and structure of genital organs; prevents interbreeding between populations.
Pre-mating (Pre-zygotic) Mechanisms - Prevent fertilisation and zygote formation; types: Habitat (separate habitats), Seasonal/Temporal (different mating seasons), Ethological (different mating behaviour), Mechanical (different reproductive organ structure).
Post-mating (Post-zygotic) Barriers - Occur after mating; types: Gamete mortality (gametes die before union), Zygote mortality (zygote dies after fertilisation), Hybrid sterility (hybrids are sterile due to failed meiosis; e.g., mule).
Significance - Isolating mechanisms promote divergence between separated populations, alter gene pools, and ultimately lead to the formation of new species (speciation).