Evidences for biological evolution (paleontology, comparative anatomy, embryology and molecular evidences

  • The organs which have the same fundamental structure but are different in functions are called Homologous organs
    Eg. ⇒ Forelimbs of frog, pigeon, lizard, bat, whale, horse, human
    Mouth parts of cockroach, mosquito, honeybee and butterfly
    ⇒ Thorn of Bougainvillea and Tendrils of cucurbita
    ⇒ Testis and ovary
    ⇒ Radish and carrot
    ⇒ Potato and ginger
  • Homology observed amongst the molecules are called as molecular homology.
    Eg. Proteins found in the blood of man and ape.
  • Homologous organs show divergent evolution with adaptive radiation.
  • The organs possessing similar functions but different in structure and origin are called as Analogous organs.
    Eg : ⇒ Wings of insect and wings of a bird / bat
    ⇒ Hands of Human and Trunk of an elephant
    ⇒ Stings of honey bee and scorpion
    ⇒ Fins of fishes and flippers of whale
    ⇒ Eye of octopus and cat
  • The presence of these analogous organs indicate a similar adoptational functional structures in unrelated groups is called as convergent evolution.
  • The organs which do not perform any function in the body, that are present in the reduced form but correspond to the fully developed functional organs of related animals are termed as vestigial organs
    Eg ⇒ nictitating membrane (plica semilunaris)
    ⇒ External car (pinna)
    ⇒ Vermi form appendix
    ⇒ Caudal vertebrae
    ⇒ Third molars
    ⇒ Hair on body
    ⇒ Male - nipples.
  • The organisms which possess the characters of 2 different groups are called connecting links.
    Eg ⇒ Euglena [b/w plants and Animals] ⇒ Echidna / platypus (egg laying mammals)
    ⇒ Peripatus [annelida and Arthopoda] [b/w reptile and mammals]
  • The reversal of an ustral characters which had either disappeared is called as Atavism. Eg. Tendency of moving pinna, long dense hairs, short fail in some babies.
  • Evolution can also proved by Emryological studies, especially by Baer's law, which states that, during embryonic development, the generalized features [Brain, spinal cord] appear first and then the specific features [hair, legs] appear.
  • Baer's law was modified by Ernst Haeckel as Ontogeny repeats phylogeny. where ontogeny is Evolutionary relationship, which means that the organism during its embryonic development resembles its ancestors nature.
  • Example : Development of the frog includes Tadpole larval stage which resembles a fish.
  • The organism repeating its ancestral history during its development is called as Biochemical recapitulation. Eg. Fishes are Ammonotelic and Tadpoles are also the same, whereas frogs are ureotelic. which could prove that frogs arise from fishes.
  • Physiological evidence / Biochemical evidence such as presence of blood, ATP, Trypsin, nucleotides and etc in all the various form of animals had strongly proven than evolution have taken place.

Part-1: Watch this video for the topic from 12:40 to 23:03

Part-2: Watch this video for the topic from 29:25 to 47:20

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