CBSE Class 10 Science 2017 · Paper 31/3 · Question 12

Organic evolution is the sequence of gradual changes that take place in organisms over very long periods of time (many generations), by which new species arise from pre-existing, often simpler, forms of life. It cannot be equated with progress because evolution only produces diversity, which is then shaped by environmental selection; it does not move towards a goal or towards 'better' forms. A newly formed species is not necessarily better than the older one - it is just different - and older, simpler designs continue to survive. Example: human beings did not evolve from chimpanzees. Humans and chimpanzees had a common ancestor long ago, which was neither a chimpanzee nor a human, and the two lines evolved separately in their own ways; neither is more 'advanced' than the other. Likewise bacteria, among the simplest organisms, still thrive in hot springs, deep-sea thermal vents and Antarctic ice - the simple design has not been replaced by a 'better' one.