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The science which deals with the study of history of life forms on earth.

The organs which performs the same function but differ in their origin and structures are called analogous organs.

The organs which have similar embryonic origin but they perform the different functions.

In some animals, the same structure developed along different directions due to adaptations to different needs This is divergent evolution and is called homology. Homology indicates common ancestry. For example, vertebrate hearts or brains. In plants also, the thorn and tendrils of Bougainvillea and Cucurbitarepresent homology. Wings of butterfly and of birds look alike. They are not anatomically similar structures though they perform similar functions. Analogy results from convergent evolution in which different structures evolve for the same function and hence have similarity. Sweet potato (root modification) and potato (stem modification) is another example for analogy.

(i) Homology 

(ii) Analogy 

(iii) Analogy 

(iv) Analogy 

(v) Analogy 

(vi) Homology

It is the branch of science that deals with fossils.

Homology refers to the similarities in the fundamental anatomy and embryology of organs of different groups of plants and animals.

It refers to structurally different organs evolving for the same function in different group of plants and animals.

It is the evolutionary process by which same structures developed differently due to different needs.

It is the evolutionary process in which different species starting from a common point in a geographical area radiate to other geographical areas.

Wings of birds and forelimbs of horse.

Amino acids.

Louis Pasteur dismissed the theory of spontaneous generation and demonstrated that life came from pre-existing life. He took two long-necked flasks. He left one flask with a straight neck and the other was bent to from an ‘S’ shape. He put sterile broths in both the flasks. He placed killed yeast in pre-sterilised bent flask and the other flask was left open to air. 

After several weeks he observed that the straight neck flask was discoloured and cloudy, while the curved flask had not changed. Thus he concluded that the germs in air were able to fall unobstructed down the straight necked flask while they got trapped in the curved flask.

1. Mutations or discontinuous variation are transmitted to other generations. 

2. In naturally breeding populations, mutations occur from time to time.

3. There are no intermediate forms, as they are fully fledged. 

4. They are strictly subjected to natural selection.

Cope, Osborn, Packard and Spencer.

Mutation theory was put forth by Hugo de Vries. Based on the experiments in Oenothera lamarckiana (The evening primrose plant).

Ernst Von Haeckel proposed the theory of recapitulation, which states that life history of an individual briefly repeats the evolutionary history of the race.

(b) August Weismann

(c) carbon dating

Migration may cause enrichment of the gene pool of such alleles that are being selected for, or blur the effects of selection through replenishment of alleles that were selected against by nature.

(c) phylogeny

Hardy-Weinberg principle states that the sum of allelic frequencies in a population remains constant. Five factors are known to affect Hardy-Weinberg equilibrium. These are gene migration or gene flow, genetic drift, mutation, genetic recombination and natural selection.

Whales, bats, Cheetah and human (all mammals) share similarities in the pattern of bones of forelimbs. Though these forelimbs perform different functions in these animals, they have similar anatomical structure. All of them have humerus, radius, ulna, carpals, metacarpals and phalanges in their forelimbs.

Hence, in these animals, the same structure developed along different directions due to adaptations to different needs. This is divergent evolution and these structures are homologous. Homology indicates common ancestry. Driving force behind the divergent evolution is adaptation in different environments.