CBSE Class 10 Science 2019 · Paper 31/4/2 · Question 6

Evolution: The sequence of gradual changes that take place in living organisms over millions of years, by which new species arise from existing ones. Why evolution cannot be equated with progress: Evolution only generates diversity, and the environment selects what suits it. More complex body designs have appeared over time, but the simpler, older designs have not been replaced; they continue to survive and flourish and are equally efficient in their own habitats. Examples: (i) Bacteria, among the simplest and earliest forms of life, still thrive, even in the most hostile habitats such as hot springs, deep-sea thermal vents and the ice of Antarctica. (ii) Humans have not evolved from chimpanzees; both evolved from a common ancestor along separate lines, so humans are not the pinnacle of evolution but one more species among the evolving forms of life.