Evolution

Biological evolution


  • There were 3 conditions for the origin of life
    ⇒ continuous supply of replicators
    ⇒ copying error during replication
    ⇒ system must have required a continuous supply of free energy.
  • Biological evolution started with the formation of pre/protobionts which are non living structures that led to the formation of first living cells from which the more complex cells have evolved.
  • The 2 prebionts are
    Oparin ⇒ coacervates [aggregation of colloidal particles in liquid phase that consists of carbohydrates, proteins, lipids and nucleic acids surrounded by a non-biological membranes
    Sydney Fox ⇒ Micro spheres [Microscopic membrane bound spheres formed when protenoids are boiled in water and allowed to cool. Protenoids are produced by dehydration synthesis of amino acids at 180°C]
  • Oldest known fossil ⇒ Stromatollites [sheet formed over sedimentary rocks which contained a species of Blue green Algae, called Archaeospheroides barbetonensis].
  • Evolution of modes of Nutrition
    (heterotrophs)
              ↓
    (Chemoheterotrophs)
              ↓
    (Autotrophs)
              ↓
    (Chemoautotrophs)
              ↓
    (Photo auto trophs) - Eg. Cyanobacteria
  • As the number of photoautotrophs increased, O2 was released in the sea and atmosphere which is termed as O2 revolution.
  • As O2 accumulated in atmosphere, the UV light changed some of the O2 into Ozone.
    2O2 + O2 → 2O3
  • Origin of Eukaryotes is of two types
    ⇒ Symbiosis [Margulis]
    ⇒ Origin by Invagination
  • Symbiotic origin :
    ⇒ Predator host cell  +  aerobic bacteria  ⇒  Eukaryotic animal cell
                              [Contributing Mitochondria]
    ⇒ Predator host cell + aerobic bacteria + cyanobacteria  ⇒ Eukaryotic plant cell.
                                     [mitochondria]      [chloroplast]
  • Three domains of life [Carl Woese]
    ⇒ Eubacteria
    ⇒ Archae
    ⇒ Eucarya
  • Finally, it is concluded that the life originated from ocean.
    ⇒ Evidences for organic Evolution
  • The study of fossils is called as Palaeontology.
    ⇒ Leonardo da Vinci [The Father of Palaeontology]
    ⇒ George Cuvier [The Founder of modern Palaeontology]
  • The fossils of spores, Pollen grains and other microscopic structures are called micro fossils (or) Palyno fossils.
  • Age of the fossils can be determined by following methods
    ⇒ Clock of the rock method / Radioactive clock
    ⇒ Radioactive carbon method
    ⇒ Potassium - argon method
  • The first geological time scale was developed by Gioranni Avdesina. The history of the earth has been divided into a number of major divisions called eras, which are sub divided into periods. The modern periods are further divided into epochs.
  • The fossil record contains some transitional link forms called missing links [also called as connecting links].
    Eg. Archaeopteryx [connecting link between birds and reptiles]
  • Evolution of Vertebrates :
    Ostracoderms
             ↓
    Acanthodians
             ↓
    Placoderms
  • Evolution of horse :
    Eohippus [renamed as Hyracotherium]
          ↓
    Mesohippus [Intermediate horse]
          ↓
    Merychippus [ruminating horse]
          ↓
    Pliohippus [first, one toed horse]
          ↓
    Equus [modern horse]

Watch this video for the topic from 1:18 to 12:40

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