Statement I: According to Darwin, variations within a population lead to differential survival and reproduction rates among individuals.
Statement II: Lamarck's theory is centred on the idea that the use or disuse of organs could lead to changes in traits across generations.
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Both statements I and II are correct.
Darwin and Lamarck both said that living forms evolve, but they gave different reasons for how it happens.
Statement I: According to Darwin, variations within a population lead to differential survival and reproduction rates among individuals. — True. Darwin saw that the members of a population differ. Those whose traits suit the environment survive better and leave more progeny. He called this natural selection.
Statement II: Lamarck’s theory is centred on the idea that the use or disuse of organs could lead to changes in traits across generations. — True. Lamarck said evolution was driven by use and disuse of organs, and that such acquired changes were passed on. His example was the long neck of the giraffe. The book adds that this idea is no longer accepted, but the statement only describes his theory, so it is true.
NCERT Extract:
Evolution of Life Forms – A Theory – “… Those characteristics which enable some to survive better in natural conditions (climate, food, physical factors, etc.) would outbreed others that are less-endowed to survive under such natural conditions. Another word used is fitness of the individual or population. The fitness, according to Darwin, refers ultimately and only to reproductive fitness. Hence, those who are better fit in an environment, leave more progeny than others.”
Biological Evolution – “… Even before Darwin, a French naturalist Lamarck had said that evolution of life forms had occurred but driven by use and disuse of organs. He gave the examples of Giraffes who in an attempt to forage leaves on tall trees had to adapt by elongation of their necks.”