Q4. Give two animal examples and one plant pair of homologous organs from NCERT.
Animals: the forelimbs of whales, bats, cheetahs and humans; vertebrate hearts or brains. Plants: the thorn of Bougainvillea and the tendril of Cucurbita (NCERT pages 114–115).
Q5. What argument does NCERT draw from the breeds of dogs?
Intensive breeding by humans has created breeds that differ from one another but are still of the same group; if humans could create new breeds within hundreds of years, nature could have done the same over millions of years (NCERT page 115).
Q6. What do the rapid appearance of pesticide-resistant varieties and antibiotic-resistant microbes tell us about the nature of evolution?
That evolution can happen by anthropogenic action in months or years, and that evolution is not a directed process in the sense of determinism but a stochastic process based on chance events in nature and chance mutation in the organisms (NCERT page 116). Beyond the NCERT text: variation can also arise by gene transfer (Wikipedia, “Antimicrobial resistance”, facts in our words), and selection itself favours the variants that leave more progeny.
Q7. How do similarities in proteins and genes support evolution?
Similar proteins and genes performing a given function in diverse organisms point to common ancestry, just as structural similarities do (NCERT page 115).
Q8. What does the study of fossils in successive rock layers show?
That life forms varied over time and certain forms are restricted to certain geological time spans, so new forms of life arose at different times in the history of the earth (NCERT page 113).