Evolution std 12th neet
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Evolutionary biology is the study of the history of life forms on Earth. There are several theories for how life originated, including that life came from outer space or spontaneously generated from non-living matter. The currently dominant theory is that the universe began in a massive explosion around 13 billion years ago known as the Big Bang. Over time, gravity caused gas and dust to condense, forming the sun and planets. Earth formed around 4.5 billion years ago without an atmosphere. Early theories of organic evolution include those proposed by Lamarck and Darwin, with Darwin's theory of descent with modification through natural selection now the prevailing explanation of how evolution has occurred. Evidence for evolution comes from morphology, embryology, physiology and paleontology.
Evolution std 12th neet
- 3. Evolution Evolutionary Biology is the study of history of life forms on earth Flora :- Plant group and fauna :- Animal Group The Origin of life is considered unique event in the history of universe The universe is vast
- 4. The word evolution means to unfold or unroll or to reveal hidden potentialities. Evolution simply means an orderly change from one condition to another. It can be best explained by Darwin’s concept of ‘Descent with modification’. This is the story of origin of life and evolution of life forms or biodiversity on Planet earth in the context to evolution of earth and against the background of evolution of universe itself. What is Evolution? Evolution term was introduced by Herbert Spencer.
- 5. THEORIES FOR ORIGIN OF LIFE: 1. Theory of special creation: 2. Cosmic panspermia theory: 3. Theory of spontaneous generation (Abiogenesis/Autogenesis) 4. Others like Biogenesis (F. Reddy),Harvey and Huxley Meteority Theory :- (Other planet, (Suddenly Evolution from cosmozoa), Theory of catatrophs:- (Qvier Propoesed, Sudden revoultion at different intervals time)
- 6. 1. Theory of special creation: The greatest supporter of this theory was Father Suarez. This is mythology based theory. All elements were created within Six days This theory has three connotations – (a) All living organisms that we seen today were created as such. (b) The diversity was always the same since creation and will be the same in future. (c) The earth is about 4000 years old. From fossils records and their dating, we can conclude that earth is very old, not thousands of years as was through earlier but billions of years old
- 7. 2. Cosmic panspermia theory: Some scientists believe that life came from outer space. Early Greek thinkers thought units of life called spores were transferred to different planets including earth. ‘Panspermia’ it still a favorite idea for some astronomer.
- 8. 3. Theory of spontaneous generation (Abiogenesis /Autogenesis) This hypothesis was supported by ancient Greek philosophers. According to this theory life came out of decaying and rotting matter like straw, mud, etc spontaneously. They believed that the mud of Nile river could give rise to fishes, frogs, crocodiles etc when warmed by light rays.
- 9. BIG BANG THEORY Proposed by Abbe Lemaitre. According to it, the universe originated about 20 billion years ago due to a thermonuclear explosion of a dense entity. This single huge explosion which is unimaginable in physical terms, is called as big bang. It attempts to explain to us “ Origin of Universe” Universe Explosion and Expanded, temp. came down. Hydrogen and helium sometime formed later.
- 10. Gases condensed under gravitation and formed disc like structure is called nebula (made up of small particles and atoms ) e.g Solar nebula formed solar system) and formed Milky way. The very hot central part of solar nebula became still hotter and converted into the sun. This is called Nebular Hypothesis Later on, due to condensation of atoms and dust particles moving around the sun other planets were formed. In the solar system of the Milky Way galaxy, earth was supposed to have been formed about 4.5 billion years back There were no atmosphere on early earth.
- 15. THEORIES OF ORGANIC EVOLUTION Historically there are 3 Theory 1. Lamarck 2. Darwin 3. De vries Mutation
- 16. EVIDENCED FOR EVOLUTION MORPHOLOGY EMBRYOLOGY PHYSIOLOGY PALAENTOLOGY- Study of fossils is called palaeontology. E.G. Print fossils: Fossilized impressions of foot, wings, leaves, stem etc…………..