Question 16.
Answer the following question.
Explain the theory of evolution and mention the proof supporting it.
Answer:
According to this theory, protoplasm the first living material was formed in ocean. After that unicellular organisms were formed. With the gradual changes in unicellular organism, multicellular and complex organisms were formed. These changes were slow and gradual which took 300yrs and more. Progressive development of plants and animals from the ancestors having different structural and functional organization is called evolution. There are many proofs supporting the theories.
I. Morphological evidences: Similarities in morphology and physical structure prove that they have the same origin and common ancestors. For examples structure of mouth, position of nostrils, ear pinnae and thick hair on full body in animals like dog, goat and sheep.
II. Anatomical evidences: Organs of different animals are dissimilar in function but similar in structures of bones and bony joints shows that these animals may have common ancestors. For Examples human hand, cat’s foreleg, patagium of bat and flipper of whale perform different function but their bones are similar in structure.
III. Vestigial organs as evidences: Underdeveloped useless organs in organisms are called as vestigial organs. Such organs are useless in some organisms but these organs are useful in other organisms. For examples appendix useless in humans but functional in cattle. Ear pinna muscle useless in human but useful in monkeys.
IV. Paleontological evidences: many organisms get buried under the ground due to disasters like flood, volcano, earthquake. Remnants and impression of these organisms are preserved underground and are called fossils. Study of fossils is very important for the study of evolution.
V. Connecting links: Some plants and animals have some morphological characters by which they can be related to different groups are called connecting links. Example Lung fish resembles the fish in having paired fins, gills and scales on its body, but it respires through lungs like amphibians. Thus, lung fish acts as a connecting link between fish and amphibians.
