(3)

Flippers of Penguins and Dolphins are considered as an example of convergent evolution. These are analogous that structures are not anatomically similar structures but evolved for the same function and hence having similarity i.e., for swimming. It is the similar habitat that has resulted in selection of similar adaptive features in different groups of organisms but toward the same function.

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Flippers of penguins and dolphins are pair of analogous organs.

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Herbicide resistant weeds, drug resistant eukaryotes and man-created breeds of domesticated animals like dogs are examples of evolution by anthropogenic action. Darwin’s Finches of Galapagos islands are example of natural selection, adaptive radiation and Founder’s effect.

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Embryological support for evolution was disapproved by Karl Ernst von Baer. He noted that embryos never pass through the adult stages of other animals.

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Analogous structures are result of convergent evolution, i.e., different structures evolving for the same function and hence having similarity. For example, the eye of the octopus and of mammals, the flippers of penguins and dolphins.

(1)

Homologous organs are those organs which have the same fundamental structure but are different in functions. Wings of birds and forelimbs of horse show homology because skeletal parts of their forelimbs are similar in structure and arrangement but have different functions.

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Eye of octopus, bat and man are examples of analogous organs showing convergent evolution.

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Homologous organs have same fundamental structure but different functions. The wing of a bird and flipper of a whale are structurally forelimbs, which consist of humerus, radio-ulna, carpals, metacarpals and digits but they perform different functions. The wings of birds help them to fly while flipper helps the whale to swim.

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The organs which have similar functions but are different in their structural details and origin are called analogous organs. The analogous structures are the result of convergent evolution.

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Analogous organs are the organs which have similar function but are different in their structural details and origin. The analogous structures are the result of convergent evolution. The wings of an insect are analogous to wings of a bird because the basic structure of the wings of the insects is different from the wings of bird. However, their function is similar.

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Natural selection is the most widely accepted theory concerning the principal causal mechanism of evolutionary change propounded by Charles Darwin and Alfred Russel Wallace. It results from the differential reproduction (some members of a population produce abundant offspring, some only a few and still others none), one phenotype as compared with other phenotypes in the same population. This determines the relative share of different genotypes which individuals possess and propagate in a population. Industrial melanism supports evolution by natural selection. It is an adaptation where the moths living in the industrial areas developed melanin pigments to match their bodies to the tree trunks.

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The organs which have the same fundamental structure but are different in functions are called homologous organs. These organs follow the same basic plan of organisation during their development. But in the adult condition, these organs are modified to perform different functions as an adaptation to different environments. The forelimbs of cat, lizard, whale and bat have the same basic structural plan. In each case the forelimb consists of humerus, radio-ulna, carpals, metacarpals and digits. The skeletal parts of the forelimbs of all these vertebrates are similar in structure and arrangement. But the forelimbs of these animals have different shapes and functions. In lizard they are used for walking, in cat for running, in whale for swimming and in bat for flying.

(1)

Sweet potato is a root modification while potato is a stem modification but both of them have same function. Analogous structures are not anatomically similar structures though they perform similar functions.

Analogous structures are the result of convergent evolution.

• Homologous organs are anatomically similar but they do not perform similar function. Homologous organs are the result of divergent evolution.