Biology · Evolution · NEET
No. Evolution is the slow change in the gene pool of a population over time. Speciation is one result of evolution — the point where a group changes so much and becomes so isolated that it forms a new, separate species. So all speciation is evolution, but not all evolution leads to a new species.
In allopatric speciation, a population is split by a physical barrier like a mountain, river or ocean (geographical isolation), and the two separated groups slowly become different species. In sympatric speciation, a new species forms even without a physical barrier — the groups live in the same area but stop interbreeding (for example due to a large mutation or a change in behaviour). NCERT stresses geographical isolation and reproductive isolation as the key ideas.
Genetic drift is a random change in allele frequency, and it has a strong effect in a small, isolated population. NCERT states that sometimes the change in allele frequency in the new sample of a population is so different that they become a different species. The small drifted group becomes the founders — this is the founder effect. So drift alone, by chance, can push a small isolated group into becoming a new species.
As long as two groups can freely interbreed, gene flow keeps mixing their genes and keeps them as one species. Speciation needs the gene flow to stop. Reproductive isolation (they can no longer produce fertile offspring together) locks in the genetic differences, so the two groups drift apart permanently and become separate species.
Yes. Adaptive radiation is the evolution of many different species from one ancestor spreading into many vacant habitats — Darwin's finches and Australian marsupials are the NCERT examples. Each finch adapted to a different food/habitat and became a separate species, so adaptive radiation is speciation happening many times from one starting point.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Speciation is the origin of a new species from a pre-existing one, occurring when a population becomes reproductively (often first geographically) isolated so its gene pool separates.
The five factors that disturb Hardy-Weinberg equilibrium: gene flow (migration), genetic drift, mutation, genetic recombination, and natural selection — plus geographical and reproductive isolation that keep the groups apart.
When drift makes the allele frequency of a small isolated group very different from the parent population, that small group becomes the founders of a new species. This chance-driven route is called the founder effect.
Yes. From one seed-eating ancestor, many finch species with different beaks evolved on the Galapagos Islands. This adaptive radiation is repeated speciation into vacant habitats.
