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Evidences of evolution
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The wings of a bird and the wings of an insect are:
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Forelimbs of cat, lizard used in walking; forelimbs of whale used in swimming and forelimbs of bats used in flying are an example of:These forelimbs have the same basic bone structure but perform different functions, so they are homologous organs (divergent evolution).
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Which one of the following are analogous structures:Gills of prawn and lungs of man both carry out respiration but differ in origin and structure, so they are analogous.
The other pairs are homologous structures. -
The eye of octopus and eye of cat show different patterns of structure, yet they perform similar function. This is an example of:The eyes of octopus and cat differ in structure and origin but do the same job, so they are analogous organs.
Analogous organs arise by convergent evolution. -
Which one of the following options gives one correct example each of convergent evolution and divergent evolution?Convergent evolution gives analogous structures: different origin, similar function. Eyes of octopus and mammals are an example (so are wings of butterflies and birds).
Divergent evolution gives homologous structures: same origin, different functions. Bones of the forelimbs of vertebrates are an example (so are thorns of Bougainvillea and tendrils of Cucurbita).
So the correct pairing is eyes of octopus and mammals (convergent) and bones of forelimbs of vertebrates (divergent). -
Which one of the following pairs of items correctly belongs to the category of organs mentioned against it?Nephridia are the excretory organs of the earthworm, and Malpighian tubules are the excretory organs of the cockroach. Both remove nitrogenous wastes, so this pair correctly belongs to the category of excretory organs.
Wings of a honeybee and wings of a crow have different origins and structures but perform the same function of flight, so they are analogous organs, not homologous.
Thorn of Bougainvillea and tendrils of Cucurbita have the same origin (both are modified axillary buds) but different functions, so they are homologous organs, not analogous.
The nictitating membrane (plica semilunaris) is a vestigial organ in the human eye, but the blind spot is not vestigial; it is the functional point where the optic nerve leaves the retina.
So the correctly matched pair is nephridia of earthworm and Malpighian tubules of cockroach - Excretory organs. -
An important evidence in favour of organic evolution is the occurrence of -Homologous organs have the same basic structure and origin but different functions, such as the forelimbs of the whale, bat, cheetah and man.
They show that these organisms have descended from a common ancestor and have diverged (divergent evolution), so they are strong evidence for organic evolution.
Vestigial organs are reduced, functionless organs that were fully developed and functional in the ancestors, such as the vermiform appendix and the nictitating membrane in man.
Their presence can be explained only if the organism has evolved from ancestors in which these organs were useful, so they too are evidence for evolution.
Analogous organs have different origins and only a similar function; they result from convergent evolution and do not indicate common ancestry.
So the important evidence is the occurrence of homologous and vestigial organs.