In this blog, we are going to discuss various evidence of evolution. The presence of more common characteristics suggests the closeness of the species. Also, the more closely related species are supposed to have had a common ancestor in the more recent past.

Let us take an example to understand this better. Here, the boy and the girls are brother and sister, and so are closely related. This is because they have common ancestors in the first generation before them, that is, their parents.

On the other hand, this girl and her first cousin are a little less related than the girl and her brother, because though the cousins do have common ancestors as their grandparents, they are in the second generation before them.

Therefore, we can say that classification of species is in fact a reflection of their evolutionary relationship. We can thus form small groups of species with recent common ancestors, then super-groups of these groups with more distant common ancestors, and so on. Theoretically, moving backward will take us to single species at the very beginning of evolutionary time.

There is much evidence of evolution that can help us in tracing evolutionary relationships.

Evidence of evolution can be categorized as-

� Morphological and Anatomical Evidences
� Embryological Evidences
� Paleontological Evidences

Embryological evidence of evolution

The similarity among the early embryos of vertebrates shows that they have common ancestors.

Paleontological evidence of evolution

Paleontology is the study of past life based on fossil records. The study of fossils also helps us in tracing evolutionary relationships. Fossils are remains or impressions of the dead animals and plants that lived in the remote past. For example, The fossil bird, Archaeopteryx lived in the Jurassic period about 180 million years ago. It had feathers, fused bones, and a beak. Like reptiles, they had their teeth in jaws, claws, forefingers, and a long tail. This suggests that birds have evolved from reptiles.

Morphological and anatomical evidence of evolution

These pieces of evidence are based on the similarities in the external and internal features of the different organs in organisms.

Based on this, they are categorized as:

1. Homologous Organs
2. Analogous Organs
3. Vestigial Organs

Homologous Organs

There are a number of organs in different groups of plants and animals which have a similar basic structure and embryonic origin but are used for different functions. For example, the forelimbs of a frog, a lizard, a bird, and a human being show similarities in basic structure and development but are used to perform different functions.

� The forelimbs of a frog help the animal to prop up the front end of the body at rest and act as a shock absorber� The forelimbs of a lizard are modified for creeping movement� Forelimbs of a bat are modified for flying.� While, the forelimbs of a bird are used for grasping

The basic similarity in the forelimbs of these different vertebrates indicates that all these vertebrates had a common ancestor who had five-digited or pentadactyl limbs which got modified according to the special needs of the subsequent generations during the course of evolution.

Analogous Organ

Analogous organs are the ones that are quite different in fundamental structure and embryonic origin but perform the same function and may even superficially look-alike in entirely different species. For example, the wings of a butterfly and a bird.

The wings of a butterfly are folds of a membrane supported with a few muscles, while the bird�s wings are formed of limb bones covered with flesh, skin, and feathers. The insects and birds, in fact, have evolved from separate ancestors but use their wings to perform the same function i.e. flying. A similar example of analogous organs is that of the wings of a bat and a bird.

Vestigial Organs

The organs which occur in reduced or redundant form and are useless to the possessor, but are homologous to the fully developed functional organ in the ancestors or the related forms are called vestigial organs. Few examples of vestigial organs are The vermiform appendix of the large intestine and the nictitating membrane in the human eye.

Read More: Rules for Inheritance of Traits: Mendel�s Contributions- Science Class 10