NCERT Solutions for class 12 Biology Chapter 7
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Solutions for 12 Biology Chapter 7
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Important Terms on 12 Biology Chapter 7
- Artificial Selection: It is the process carried out by man to select better breeds of plants and animals.
- Founders Effect: A genetic drift in human population where a population in a new settlement have different gene frequency from that of the parent population. The original drifted population said to be founder.
- Gene Pool: Sum total of all the genes in a population.
- Genetic Drift: Chance elimination of genes of certain traits from a population due to migration or death.
- Saltation: Single step large mutations.
- Speciation: It is the formation of new species from the pre-existing ones.
- Organic (Biological) Evolution: Changes at the characteristics/features of organisms or groups of such population over a number of generations.
- Homologous organs: These have same basic structure and embryonic origin but perform different functions in different species.
The Theories of Origin of Life
- Theory of Special Creation: According to this theory God has created life within 6 days.
- Theory of Spontaneous Generation: According to this theory life originated from decaying and rotting matter like straw and mud.
- Panspermiatic Theory: According to this theory life came from space in the form of spores called Panspermia.
- Modern Theory or Oparin-Haldane Theory: According to this theory life originated upon earth spontaneously from non-living matter. First inorganic compounds then organic compounds were formed in accordance with ever changing environment conditions. This is called chemical evolution. The conditions on earth were high temperature, volcanic storms, reducing atmosphere (without free oxygen) containing methane and ammonia.
Evolution of Man
- About 15 mya, primates called Dryopithecus and Ramapitheus were existing.
- Dryopithecus: Were more ape-like, live in Asia, Africa and Europe. Walk semierect, Hand & Skull were monkey like.
- Ramapithecus: First man-like, walk straight on legs, not taller than 4 feet.
- Australopithecines: 2 mya, lived in east african grassland, hunted with stones, ate fruits, Teeth larger.
- Homo habilis: 2 mya, brain capacity 650-800cc, did not eat meat, dentition like humans.
- Homo erectus: 1.5 mya, brain capacity 900cc, ate meat, walk erect.
- Homo sapiens: 5 lakhs years ago, in Africa, and spread to all parts of world.
- Neanderthal man: 40,000-1,00,000 years ago, brain capacity 1400cc, broad forehead, lives in caves, use hides to protect their bodies.