Evolution Important Notes For NEET



        Origin of life and evolution are important aspects of life. The term which refers to origin of life is called biopoiesis.

        Universe is the vast space constituting stars, planets and rocks. The universe is originated as a result of Big Bang theory.

        Primitive surface of earth was in Molten state and there was no atmosphere. Later on it resulted in emission of CO₂, H₂O, CH₄ and NH₃ as a result of cooling.

        Early earth represented reducing atmosphere because of availability of hydrogen atoms and less oxygen molecules.

        Many theories were put forward by scientist for origin in life, some of these have experimental proofs while some do not have.

        Theory of special creation states that life is created by some supernatural power. It was given by Father Saurez.

        Theory of spontaneous generation also called theory of abiogenesis states that life is generated from non-living materials. It was supported by Greek philosophers and cases were also cited for the production of various insects and animals.

        Theory of biogenesis states that life originated from pre-existing life. It was supported by many scientists and different experiments were also performed.

        Theory of cosmozoic origin states that life is coeternal and living and non-living objects were formed simultaneously.

        Theory of panspermia proposed that presence of advanced civilisation on other planets in our galaxy. It was supported by genetic codes and role of molebdenum.

        Theory of catastrophism assumed that a catastroph occurred at beginning of next new age and new creation evolved.

        Modern theory of origin of life was hypothesised by Al Oparin supported by JBS Haldane. According to this, life originated after a long period of abiogenic molecular evolution that bought a gradual change in organic and inorganic compounds.

        The whole process of origin of life is divided into two major categories chemical evolution and biological evolution.

        Chemical evolution occurred in different phases which include atomic phase, formation of early molecules, simple organic molecules, large molecules and finally formation of organic compounds.

        Biological evolution involves the process of inheritance of genetic changes, it includes formation of coacervates, protocells and origin of prokaryotes.

        Evolution of various modes of nutrition is studied under different categories such as chemoheterotrophs, chemoautotrophs and photoautotrophs.

        With the increase in number of photoautotrophs a huge amount of oxygen was liberated in the sea which lead to oxygen revolution.

        Eukaryotes originated due to oxygen revolution about 1500 million years ago. There were two modes by which they originated symbiotic and invagination.

        Ribozyme and Meteorites have an important part in origin of life because of the presence of nucleotides.

Continue Your Revision - Evidences Of Evolution