EVOLUTION -BIOLOGY CLASS 12

TAARIKA MOHAN

EVOLUTION COMPLETE NCERT COVERED

1.Origin of life is considered as unique event in the history of universe.

2. Universe is almost 20 billion years old.

3.Big bang theory gave an idea of origin of universe.

4.Earth is almost 4.5 billion years old. 

5.Early earth :

  • Had no atmosphere
  • Was covered with CO2,CH4,water vapor and NH3.
  • Had reducing atmosphere.
  • O2 combined with NH3 and CH4 to form water.
6.Life appeared- After 500 million years of formation of earth i.e., almost 4 billion years ago.

7.Theory of panspermia:

  • Early Greek thinkers+Astronomers
  • Units of life called SPORES were transferred to different planets.
8.Theory of spontaneous generation-Life came out of rotting and decaying matter like straw and mud. This was disproved by LOIS PASTEUR.

PASTEUR'S EXPERIMENT:

  • Life comes only from pre-existing life.
  • Pre-sterilized flask+killed yest+NO AIR=No life
  • Pre-sterilized flask+killed yest+AIR=Life.
  • Did not answer how first life form came on earth.
9.CHEMICAL EVOLUTION:

  • Given by Oparin(Russia) and Haldane(England).
  • First life form came from pre-existing non-living organic molecules .
  • This is preceded by biological evolution.
10.In 1953, S.L.Miller(America) created reducing conditions in laboratory. He created electric discharge in a closed flask containing Methane,Hydrogen,Water vapor (800 'C) and he observed formation of Amino acids.

11.First non-cellular form of life-3 billion years ago.

12.First cellular forms of life-2 billion years ago.

13. Important conversion:       1 billion=1000 million.

14.Theory of Bio-genesis:

  • First form of life arose slowly through evolutionary forces from non-living molecules.
  • this is accepted by majority.
15.Theory of special creation:

  • All living organisms were created as such.
  • Diversity was always same since creation and will be same in the future.
  • Earth is about 4000 years old.
16.Charles Darwin-H.M.S.Beagle:

  • concluded that existing living forms share similarities to varying degrees, not only among themselves but also with life forms that existed millions of years ago.
  • Fitness of individual= Reproductive fitness.
  • He gave Natural Selection theory.
17.Alfred Wallace👉 Naturalist👉Malay Archipelago.

18.Geological history of earth closely correlates with biological history of earth.

19.Fossils are remains of hard parts of life forms found in rocks.

20.Embryological support for evolution 👉 Ernst Heckel.

21.Karl Ernst Von Baer 👉Disproved Embryological support for evolution."Embryos never pass through adult stages of other animals".

22.Divergent evolution=Homology=Same origin=Common ancestry.

  • Examples:
  • pattern of bones in man,cheetah,whale,bat.
  • Vertebrate heart/brain.
  • Thorn of bougainvillea and tendril of Cucurbita.
23.Convergent evolution=Analogy=Same function- Similar habitat resulted in selection of similar adaptive features.

  • Examples:
  • Wings of butterfly and bird
  • Eye of octopus and mammal
  • Flippers of penguin and dolphin.
  • Sweet potato and potato.
24.Industrial melanism-England.

  • 1850-More white winged moths-Before industrialization.
  • 1920-More dark winged moths-After industrialization.
  • No variant is completely wiped out.
25.Evolution by anthropogenic action happens in a much lesser time scale as compared to natural evolution.

26.Evolution is not a directed process in the sense of determinism,It is a stochastic process(Random phenomenon )  based on chance events in nature and chance of mutation.

27.Adaptive Radiation:

  • Observed by Darwin in Galapagos islands.
  • Process of evolution of different species of a given geographical area,starting from a point and literally radiating to other areas of geography(habitat) is adaptive radiation.
  • Examples:
  • Darwin finches,Australian marsupials,Placental mammals of Australia.
  • In the same isolated area of two different adaptive radiations(Marsupials and placental mammals) took place,now the organism of marsupial and placental mammal due to same habitat result into similar features leading to analogy!
28.Biological Evolution:

  • Evolution by natural selection is because of differences in metabolic capability of cellular forms originated.
  • rate of evolution is linked to life cycle/span.
  • There must be a genetic basis for getting selected and to evolve.Adaptive ability is inherited. It has genetic basis.Fitness is the end result of ability to adapt and get selected by nature.
  • Two key concepts of Darwinian theory are BRANCHING DESCENT and NATURAL SELECTION.
  • Lamarck👉French👉Use and disuse of organs.
  • When we describe evolution as story of world it seems to be a process.But when we describe story of life on earth it seems to be a result of process.
29.Work of Thomas Malthus on population influenced Darwin.

30. Darwin's Evolution Aspects:
  • Heritable
  • Small changes
  • Directional
31.Hugo DE Vries:
  • Evening primrose
  • Large changes
  • Sudden changes
  • Directionless
  • Random
  • Mutation
  • Single step
  • Saltation
32.Hardy-Weinberg Principle:
  • Frequency of occurrence of alleles of gene/locus is fixed and remain same through generations.
  • Gene pool(Total genes and alleles in population) is always Constant.This is called Genetic Equilibrium.
  • Sum total of all allelic frequencies is always 1.
  • Disturbance in genetic equilibrium or Hardy Weinberg equilibrium i.e., change of frequency of alleles in a population would then be interpreted as resulting in evolution.
33. Factors influencing Hardy Weinberg Equilibrium:
  • Gene migration/Gene flow(If gene migration happens multiple times it would lead to gene flow).
  • Genetic drift(By chance)
  • Mutation
  • Genetic recombination
  • Natural selection
34. EVOLUTION OF MAN:
35. Important Information:
36.Pre-Historic cave art-18,000 years ago.
37.Agriculture-10,000 years ago.
38.Skull of baby chimpanzee is more like adult human.
39.Evolution of modern man is parallel evolution to human brain and language.
**** ALL DIAGRAMS TO BE THOROUGHLY CHECKED
😊THANK YOU😊

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