EVIDENCES FOR EVOLUTION

WHAT ARE EVIDENCES FOR EVOLUTION?

Paleontological evidence:

  • Fossils are remained of hard parts of life-forms found in rocks.
  • Different-aged rock sediments contain fossils of different life-forms who probably died during the formation of the particular sediment.
  • They represent the extinct organisms (e.g. Dinosaurs).
  • A study of fossils in different sedimentary layers indicates the geological period in which they existed.
  • The study showed that life-forms varied over time and certain life forms are restricted to certain geological time-span.
  • Hence new lives have arisen at different times in the history of earth.
  • All this called Paleontological evidence.

Comparative anatomy and morphological evidence:

  • Comparative anatomy and morphology shows similarities and differences among organisms of today and those that existed years ago.

Divergent evolution:

  • Whale, bats, cheetah and human share similarities in the pattern of bones of forelimbs.
  • 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 adaptation to different needs.
  • This is divergent evolution and these structures are homologous.
  • Homology indicates common ancestry.
  • Other examples of homologous organ are vertebrate hearts and brains.
  • Thorn of Bougainvillea and tendrils of Cucurbita are present homology.

Convergent evolution:

  • Wings of butterfly and of birds look alike.
  • They are anatomically similar structure though they perform similar function.
  • Hence analogous structures are a result of convergent evolution.
  • Eye of octopus and eye of mammals.
  • Flippers of Penguins and Dolphins.
  • Sweet potato (root modification) and potato (stem modification).

Biochemical evidences:

  • Similarities in proteins and genes performing a given function among diverse organisms give clues to common ancestry.

 Embryological support for evolution:

  • Proposed by Ernst Haeckel based upon observation of certain features during embryonic stage common to all vertebrates that are absent in adult.
  • The embryos of all vertebrates including human develop a row of vestigial gill slits just behind the head but it is a functional organ only in fish and not found in any other adult vertebrates.
  • This is disproved on careful study performed by Karl Ernst von Baer. He noted that embryos never pass through the adult stages of other animals.

Evolution by natural selection:

  • Based on observation of moth population in England made in 1850.
  • Before industrialization set in, it was observed that there were more white-winged moths on trees than dark-winged or melanised moths.
  • After industrialization i.e. 1920 there were more dark-winged moths in the same area i.e. the proportion was reversed.

Evolution by anthropogenic action:

  • Excess use of herbicides, pesticides etc., has only resulted in selection of resistant varieties in a much lesser time scale.
  • This is also true for microbes against which we employ antibiotics or drugs against eukaryotic organisms/cell.
  • Hence resistance organisms/cells are appearing in a time scale of months or years and not in centuries.
  • These are the examples of evolution by anthropogenic action.
  • Evolution is a stochastic process based on chance events in nature and chance mutation in the organisms.

Leave a Reply

Your email address will not be published. Required fields are marked *

Related Articles

EVOLUTION OF MAN

Evolution means changes that occur in population over a time. Modern theory of evolution of man proposes that humans and apes derive from ape like ancestor that lived on earth few million years ago.

ADAPTIVE RADIATION

Adaptive radiation is the diversification of an ancestral group of organisms into a variety of related forms specialized to fit different environment. Darwin's finches and australian marsupial are its example.

HARDY WEINBERG PRINCIPLE

Hardy weinberg principle states that the frequencies of alleles and genotype will remain same through the generation as long as there are no evolutionary influences. There are five factors which affect hardy weinberg principle.

BIOLOGICAL EVOLUTION

Biological evolution is defined as the genetic change in a population that is inherited over several generations.

ORIGIN OF LIFE

Life was originated about 20 billion years ago. Big bang theory explain the origin of universe. Louis pasteur performed an experiment to explain the origin of life, he daid that life arise

Contact

Feel Free To Email Us .At: