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Closely related organisms show similarity in morphological characters. Organisms having similar morphology are supposed to be evolved from a common ancestor. Eg; the morphological similarity between human and ave indicates their evolution from a common ancestor. Similarly, Jackal, fox, the wolf may have been evolved from the same ancestor.
Some anatomical structure which provides evidence to the evolution are;
Organs which are similar in structure and origin but may different in appearance and function. They support divergent evolution. These organs may have been developed because of sharing of a different environment. Eg;
fig: Homologous organs
Organs which are similar in appearance and function but different in structure and origin is analogous organ. They support convergent evolution. These organs may have been developed due to sharing of a similar environment. Eg;
fig: Analogous organ
These are reduced and functionless organs which are supposed to be well developed and functional in ancestors due to environmental change and different mode of life, they become reduced and functionless. Eg;
fig: Vestigial organ
It is the sudden reappearance of ancestral characters in some individuals. Eg;
Living organisms having the characters of two different group of organisms are called connecting link. They indicate the evolution of one group of organisms from another. Eg;
Extinct organisms having the characters of two different group of organisms are called missing link. Eg;
Archeopteryx (lizard bird of Jurassic period)_______: missing link between reptiles and bird
These characters of Archeopteryxjustify that birds were evolved from reptiles. Reptiles are supposed to be the ugliest creatures, but birds are beautiful and glorious. So, birds are called glorified reptiles.
fig: Paleontological evidence
Paleontology is the study of fossils. Fossils are the dead remains of the past organisms either buried under earth crust or hardened into rocks. Fossils are formed in the stratified or sedimentary rock. so, fossil derived from deepest strata would be the oldest one. Fossil may be found in various form like an unaltered fossil, petrified fossils, impression fossil, gastrolith, coprolite. Fossil record provides following evidence to the evolution;
Organisms which have undergone very little change over the long geological time period are called living fossil. Eg; Limulus, Peripatus, Nautilus, Sphenodon, Gingko (plant).
fig: Embryological evidences
Biochemicals are the components of protoplasm. The similarity in biomolecules among the different group of organisms is called molecular homology. It indicates the common origin and gradual evolution of organisms. Some biochemical evidence is:
Serology is the study of serum. The serum is a thin fluid of blood except blood vessels. It contains varieties of proteins. Closely related organisms contain the similar type of protein in their serum. The antibody produced against an antigen of serum is called antiserum. If human antiserum is mixed with blood, white precipitation occurs, If it is mixed with the blood of ape again white precipitation occurs. It indicates the close relationship between ape and human. Whale was supposed to be a fish, but serological test indicates its close relationship between mammals.