Biology [3 marks Question Answer]

Reasons for changes in the two figures:

• Before the Industrial Revolution, a thick growth of white-colouredlichen covered the trees. As a result, the light-coloured moths were camouflaged and survived under this cover, while the dark-coloured moths were easily spotted by predators.
• After the Industrial Revolution, pollution resulted in a decline in the growth of lichens. The tree bark got exposed due to the absence of lichens. As a result, dark-colouredmoths now got an advantage of a dark background, were camouflaged and survived, while the light-coloured moths were easily picked by predators.
• This showed that in a mixed population, those moths which could adapt to the changing environment after the Industrial Revolution survived and increased in number,while the ones which could not adapt were slowly wiped out from the population.

Organs which are found in reduced or rudimentary condition and do not perform any function in the possessor are called vestigial organs or non-functional organs. They help in understanding the history of evolution and continuity of life.

1. Wisdom teeth: They are the last molars which appear last at the age of 17-20 years.
2. Vermiform appendix: It projects from the blind end of the caecum and is a functionless organ in humans. It is helpful in herbivorous mammals.
3. Pinna: It is the lobe-like part of the external ear which humans cannot move as in other mammals. As it is poorly developed, it is a vestigial organ.

Correct sequence through which modern man evolved:

1. Australopithecus
2. Homohabilis
3. Homo erectus
4. Neanderthal man
5. Cro-Magnon
6. Homo sapiens