Page 399 - General Knowledge

GENERAL KNOWLEDGE 2019

3. EVOLUTION OF LIFE
 Sequence of gradual changes which take place in primitive organisms over millions of years.
 The evidences of evolution are homologous organs, analogous organs and fossils.
 Jean Baptiste Lamarck gave the first theory of evolution.
Darwin‘s theory of evolution
 Darwin is called as the father of evolution.

 Darwin‘s theory consists of two points.
 Diverse group of animals evolves from one or a few common ancestors.
 Mechanism by which this evolution takes place is called natural selection.
 Proceeds from three observations.
 All species have variations within them. Individuals are not identical.
 Some of the variations are inherited. Some are random.
 Organisms produce more offspring than survive to become adults.
Main features of Darwin‘s theory
 Over production.
 Food and space are limited.
 Struggle for existence.
 Variations.
 Survival of the fittest or Natural selection.
 Evolution is of three types: Convergent Evolution, Divergent Evolution, and Parallel
Evolution.
 Convergent Evolution: Evolution of non-homologous organs in related species in response

to similar environmental conditions.
 Divergent evolution: Development of different characteristics in animals, closely related in
response in different environments.
 Parallel evolution: Development of similar characteristics in species, not closely related to
adaptation to similar environmental pressures.
 Fossils – Remains of dead plants or animals that lived in the remote past.
 Different kinds of fossils are Ammonite, Trilobite and Dinosaur.
Stages of evolution
First Stage
 Called as ‗Cosmic Evolution‘.
 The idea that space, time, matter, energy, natural law and information expanded from ‗big
bang‘, birth of our universe.
Second Stage
 Called as ‗Stellar Evolution‘.
 Big bang is thought to have produced only hydrogen, helium and subatomic particles.
 Hydrogen and helium are condensed into stars.
Third Stage
 Called as ‗Chemical Evolution‘.
 The only chemical elements produced by Big bang were hydrogen and helium.

 Due to incredible heat and pressure within stars, hydrogen and helium are occurred.
Fourth Stage
 Called as ‗Planetary evolution‘.

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