Biology · Evolution · NEET
No. For NEET, fitness is not about strength or size. NCERT says fitness, according to Darwin, refers ultimately and only to reproductive fitness. The 'fittest' is the one that leaves more offspring in that environment, not the one that fights best. A small, well-camouflaged animal can be fitter than a large strong one if it reproduces more.
No. Darwin knew variation existed in a population but he did not know its cause. He even ignored or stayed silent about Mendel's 'factors' (genes). The source of variation (mutation, recombination) was explained later. So in NEET, do not link Darwin himself with mutation, that was Hugo de Vries.
On his sea voyage round the world in H.M.S. Beagle, Darwin observed that living forms share similarities with each other and with life forms that existed millions of years ago, that many old forms went extinct, and that new forms arose over time. On the Galapagos Islands he studied the small black birds later called Darwin's finches. These observations led him to the idea of gradual evolution.
Branching descent means all existing life forms share common ancestors, but these ancestors lived at different periods of earth's history. Life did not appear in a straight line; it branched out like a tree. NCERT notes that homology is explained by the idea of branching descent. This is why organisms show similarities in varying degrees.
Alfred Wallace was a naturalist who worked in the Malay Archipelago. NCERT clearly states he came to similar conclusions about natural selection around the same time as Darwin, independently. NEET can ask this as a fact-match, so remember: Darwin AND Wallace both proposed natural selection.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Two ideas: (1) branching descent, all life shares common ancestors from different periods; (2) natural selection, individuals with useful heritable variations survive better and leave more offspring, so nature selects them as the mechanism of evolution.
No. Natural selection is the mechanism, evolution is the result. Darwin said natural selection acting on built-in variation over long time causes gradual evolution of life forms from common ancestors.
Everyday fitness suggests strength or health. Darwinian fitness means only reproductive success, the number of offspring left behind. This is a very common NEET trap, so keep fitness equal to reproduction.
Darwin travelled on H.M.S. Beagle. On the Galapagos Islands he observed the small black birds later called Darwin's finches, which showed varied beaks and later became an example of adaptive radiation.
