Biology · Evolution · NEET
No. This is the most common mistake. NCERT clearly states: fitness according to Darwin refers ultimately and only to REPRODUCTIVE fitness. A small, weak-looking organism that leaves many surviving, fertile offspring is MORE fit than a big, strong one that leaves few. Fitness is measured by offspring left, not by muscles or size.
No. 'Fittest' means best suited to the given natural conditions (climate, food, physical factors), not the strongest. Those whose characteristics let them survive better in nature will outbreed the others. So the fittest is the best-adapted breeder for that environment, not the physically most powerful.
NCERT (from Organisms and Populations) links high Darwinian fitness to a high 'r' value. Here 'r' is the intrinsic rate of natural increase — basically the reproductive rate. Populations evolve to maximise reproductive fitness, i.e. a high r, in the habitat where they live. High r = leaving more offspring = higher Darwinian fitness.
No. Long life alone does not count. If it leaves no surviving, fertile offspring, its Darwinian fitness is zero, because its genes are not passed on. Fitness is about contribution to the next generation, not about how long you live.
Individuals with variations that raise reproductive fitness leave more offspring. Their favourable traits become more common in the next generation. Over many generations this is natural selection — nature 'selects' the more reproductively fit variants, so the population becomes better adapted.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Charles Darwin. He explained that in natural selection, 'fitness' refers ultimately and only to reproductive fitness — leaving more surviving, fertile offspring.
Yes. NCERT uses both terms for the same idea: the reproductive success of an individual, linked to a high 'r' value (high reproductive rate).
Evolution is a scoring chapter and NTA repeatedly tests the exact meaning of 'fitness'. Knowing it means reproductive success (not strength) helps you avoid the classic option trap and answer natural selection questions correctly.
Yes. If a physically weak organism is well suited to its environment and leaves many surviving, fertile offspring, it has high Darwinian fitness. Fitness is judged by offspring, not by body power.
