Evolution

•    Evolution is the process by which all living things have developed from primitive organisms through changes occurring over billions of years.
•    Some of the theories of origin of lifeare Special Creation, Spontaneous Generation, Theory of Catastrophism and Extraterrestrial or cosmic origin (Panspermia).
•    The Big Bang theory explain to us the origin of universe. Oparin’s theory is the most accepted hypothesis regarding origin of life according to which the first form of life could have evolved from the pre-existing non-living organic molecules.
•    Oparin of Russia and Haldane of England proposed that the first formof life could have come from pre-existing non-living organic molecules (e.g. RNA, protein, etc). It was then preceded by chemical evolution, i.e., formation of diverse organic molecules from inorganic constituents.
•    The subsequent events to show the first form of life are a conjectured story. This story is based on Darwinian ideas of organic evolution by natural selection.
•    Experimental evidence for the chemical evolution of life was provided by Harold C. Urey and Stanley L. Miller using the spark discharge apparatus.
•    Biological origin of life followed the formation of organic macromolecules.
•    The conventional religious literature shows the theory of specialcreation.
•    The geologic time scale is a chronologic scheme to describe the timing and relationships between events that have occurred during the history of Earth.
•    Evidences for evolution have been primarily derived from five sources which include:

  1. Fossil records
  2. Comparative anatomy
  3. Comparative embryology
  4. Comparative biochemistry
  5. Geographic distribution of species and
  6. Industrial melanism

•    Adaptive radiation is the development of many species from a single ancestral population.
•    Biological evolution can be defined as the changes in the populations, not to individuals and these changes must be passed on to the next generation.
•    All organisms descend with modifications from common ancestors.
•    Darwin observed three facts and made two deductions about evolution.
•    The major drawback of Darwinism was that it was highly acclaimed, but it could not explain the mode of origin and transmission of variations.
•    Before Darwin, Jean Baptiste Lamarck, a French naturalist had given the theory of evolution of life forms based on use and disuse of organs.
•    The source of variation was discovered by Hugo de Vries, who gave the Mutation theory.
•    In a randomly mating population, evolution can be measured by Hardy Weinberg principle.
•    Earth’s past has been divided into eras, periods and epochs. The major geological eras are Archaean Era, Proterozoic Era, Palaeozoic era, Mesozoic Era and Cenozoic Era.
•    Human evolution is the lengthy process of change by which people originated from ape-like ancestors.
•    Certain phenomenon like habitat fragmentation and genetic drift may emphasise these variations leading to the appearance of new species and hence, evolution.
•    Sometimes the change in allele frequency is so different in the new sample of population that they become a different species. This original drifted population becomes founders and the effect is called founder effect.
•    The study of comparative anatomy of different organisms, fossils and comparative biochemistry provides evidence for evolution.

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