Question

1. explain with examples how the following evidences are in favour of evolution in organisms.

(i) homologous organs

(ii) analogous organs

(iii) fossils

2."Only variations that confer an advantages on an individual organism will survive in a population."Justify this statement.

Answer 1

hiii dear ,

●Ans-1 ▪▪▪

i)Homologous organs:-The homologous organs are similar in form (or are embryologically same), but perform different functions in different organisms.These provide strong evidence in the favour of evolution, for example:-The bone structure observed in wings of birds, wings of bats, flippers of dolphins, and arms of human beings resemble with each other,Though they look strikingly different on the outside and though they vary in function but they are very similar in skeletal structure.

ii)Analogous organs:-The organs that have different origins but perform the same function are called analogous organs. For example, wings of birds and wings of insects; wings of birds and wings of bats (bird wings are made of feathers, while bat wings are folds of skin) all these organs provide evidence that their origin is different but they are similar in structure.

iii)Fossils are the impressions of dead organisms, the impressions of these dead organisms can be compared through the history of earth and can tell a great deal about the changes that various species of organisms have gone through.

●Ans-2 ▪▪▪"only variation that confers an advantage on an individual organism will survive in a population"

Variation is the difference shown by one type of organism. There are various causes of variation like sexual reproduction, mutation, Geographical isolation etc. 

For example- In a small population of red colour beetles, variation occurred in due coarse of time and their colour changed to green. Earlier these red beetles were eaten by crow but due to variation, they  were able to hide themselves under the leaves and thus increased their chances of survival.

So this variation proved as an advantage for them in their survival, hence it was naturally selected and transferred from one generation to other.


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