Define evolution. How does it occur? Describe how fossils provide us evidences in support of evolution.
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Answer:
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Explanation:
Evolution is the gradual process of accumulation of adaptive changes in population’s genetic makeup through successive generations. Mutations produce sudden, discontinuous variations which accumulate in the gene pool. These random variations are acted upon by natural selection that favors, through differential reproduction, only those which confer survival and/or reproductive advantage to the individuals over others. Accumulation of these adaptive variations in lineages over generation makes them better adapted to existing environmental conditions. Further, reproductive isolation of populations of species by geographical and/or physiological barriers leads to formation of new species i.e. evolution.
Fossils are the preserved remains of ancient organisms and are formed by their burial, rot away of soft parts. Over time sediment builds over the top and press downs the buried remains. The hard bony skeleton of animals and woody parts of plants are preserved by mineralization with simultaneous transformation of sediment into rock due to pressure and chemical reactions. Thus, as one moves from lower to upper strata of these rocks, older fossils are found in lower strata while the recent one are found in upper strata. Respective location of fossils in different strata and the anatomy and physiology exhibited by them represent the evolutionary trend of different taxonomic groups and individual forms over different geographical periods. Further, transitional fossil organisms (carrying characters of two different present day groups; missing links or connecting links) provide proof for evolutionary relationship between different groups of organisms and thereby establishing evolutionary sequence.
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Answer:
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Explanation:
Evolution: The term ‘evolution’ means ‘unrolling or unfolding’. It has been derived from Latin word evolve = unfolding). It is defined as the process of gradual and orderly change from one condition to another. Such gradual and orderly changes are taking place in all the living as well as non-living things.
Therefore, evolution may be:
- Inorganic
- Organic
- Inorganic evolution: It explains the changes that are taking place in non-living objects.
- Organic evolution: It explains the gradual and orderly change in living organisms with time since the beginning of life. The process of evolution is continuous and it will never come to an end.
How Evolution Occurs: Evolution is a very complex and extremely slow process. There is an inhibit tendency to variation during reproduction because of errors in DNA copying and The random changes in gene frequencies occurring by chance and not under the control of natural selection are called genetic drift. Genetic drift is an evolutionary force operating in small populations. Gene frequency in small populations changes by chance. In small populations some genes may be best or reduced and other may increase by sheer chance irrespective of their selective advantage or disadvantage. Fossils provide one of the most acceptable evidences in support of evolution as we can study the evolutionary past of individuals in the form of their fossils. Study of fossils helps us to know about evolution/link between two species. We must ascertain the evolutionary order by dating the fossils. For example, if we dig earth to locate fossils, we would find that “those fossils closer to surface will be more recent origin than fossils that we find in deeper layers we can date fossils by detecting ratio of different isotopes of same element.”
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