7.organic evolution

• Panspermia theory of evolution suggests that life might have existed elsewhere in the universe in the form of resistant spores called panspermia
• Life might have reached Earth accidentally according to the Panspermia theory
• Prebiotic soup is described as the ocean where hydrocarbons reacted with ammonia and water to produce simple organic molecules like sugars, amino acids, fatty acids, purines, and pyrimidines
• These molecules later formed nucleosides and nucleotides
• The term "prebiotic soup" was coined by J.B.S. Haldane
• Eukaryotes evolved through two processes
• Some aerobic bacteria might have entered aerobic prokaryotes and transformed into mitochondria and plastids, leading to the production of primitive eukaryotes
• The plasma membrane might have infolded to form the endomembrane system, contributing to the evolution of eukaryotes
• Urey and Miller used a mixture of water vapor, methane, ammonia, and hydrogen in their experiments to simulate the primitive atmosphere
• Connecting links studied include:
• Eusthenopteron between fishes and amphibians
• Seymouria between amphibians and reptiles
• Archaeopteryx between reptiles and birds
• Cynognathus between reptiles and mammals
• Biogenetic law (Theory of recapitulation): 'Ontogeny repeats Phylogeny'. This means the developmental history of an organism repeats the evolutionary history of its ancestor
• Examples of biogenetic law:

  • Caterpillar of butterfly resembles an annelid
  • Tadpole larva of frog resembles a fish with a tail and a two-chambered heart and gills
• Atavism: Sudden reappearance of some vestigial organs in a better-developed condition is called atavism
• Example of atavism: Human baby born with a tail
• Examples disproving Lamarck's inheritance of acquired characters:

  • Well-developed muscles of athletes are not inherited by their children
  • Ear pinnae pierced for ornaments in India are not inherited by any child
• Darwin's influences in formulating Natural Selection:

  • 'An essay on the principles of populations' by T.R Malthus
  • 'Principles of geology' by Charles Lyell
  • 'On the tendencies of varieties to depart from original types' by Alfred Russel Wallace
• Commonalities between Darwinism and Lamarckism:

  • Presence of variations is common to Darwinism and Lamarckism
  • Both theories recognize adaptation to the environment as a primary product of evolution
• Genetic load: Existence of deleterious genes within a population is called genetic load
• Example of genetic load: Sickle cell anaemia

  • People with homozygous (both recessive genes) condition of this gene die early due to anaemia
  • People with heterozygous (one dominant and one recessive) condition live longer and exhibit resistance to malaria
• Allopatric speciation:

  • Speciation due to geographical isolation
• Sympatric speciation:

  • Speciation in the same habitat but isolation due to interbreeding
• Scientific names of ape-like and man-like earlier primates:

  • Ape-like man: Dryopithecus
  • Man-like earlier primate: Ramapithecus
  • Man-like primate who first used hide to cover the body: Homoneanderthalensis