Morphological and anatomical evidences of evolution, Biology

MORPHOLOGICAL AND ANATOMICAL EVIDENCES -

(i) HOMOLOGOUS ORGANS -

  • The organs apparently similar or dissimilar in structure and function, but of similar embryonic origin. Term homology used by Richard Owen 1804 - 1892.
  • A detailed and extensive study showes that all of them have following characteristics.
  • A fundamental similar plan
  • Contain approximately the same 'number of bones

1056_homologous organs.png

  • e.g. Fore limbs of whale, birds, bat, horse & man.
  • Mouth parts of insect is mode up of Maxilla, mandible, Labium, Labrum and hypopharynx but are adopted for different mode of feeding.
  • When function are different then it is called divergent evolution.

(ii) ANALOGOUS ORGANS -

  • The organs that have the same function and have superficial resemblance to one another but are dissimilar structure details and origin.
  • The phenomena among widely different groups is called convergent evolution.
  • e.g. Wings in insects, birds and bats are dissimilar in structure but similar in function i.e. flying.

(iii) VESTIGIAL ORGANS -

  • The organs that are present in reduced form and are useless to the possessor but correspond to the functional organs of related past animals.
  • e.g. Appendix, muscles of pinnae, nictitating membrane, coccyx, canine teeth and third molar in man, the rudimentary pelvic girdle in python.
  • In human beings total 180 vestigial organs are known.

382_vestigial rgans.png

(iv) ATAVISM (Reversal) -

  • It is the reappearance of certain ancestral characters that had either disappeared or reduced.
  • Example. Power of moving pinna in some person, greatly developed canine teeth, exceptionally long dense hairs (Lionboy of Russia), short tail in some babies, presence of additional mammae in some individuals.
Posted Date: 10/8/2012 9:24:45 AM | Location : United States







Related Discussions:- Morphological and anatomical evidences of evolution, Assignment Help, Ask Question on Morphological and anatomical evidences of evolution, Get Answer, Expert's Help, Morphological and anatomical evidences of evolution Discussions

Write discussion on Morphological and anatomical evidences of evolution
Your posts are moderated
Related Questions
What is the classification of this phylum

Q. Fats requirement in chronic diarrhoea? Total amount of fat may be restricted as its digestion and absorption is compromised. In order to increase on the calorie density of t

HISTORICA L REVIEW Anoximander (600 B.C.) was the first western philospher who proposed the idea that "living creatures arose from the moist element". Empedocles (500 B.

Importance of Research in Nursing: It is  the responsibility of the nursing profession  to discover, verify, structure and restructure the professional knowledge through  syst

A cellular system has a total of 500 duplex voice channels. The service area is divided into 150 cells. Suggest a three different cluster size (N) values. In each case, determine

Explain Pseudocoelomates in classification animal kingdom? In terms of body organization, Pseudocoelomates fall between the Acoelomates and the Coelomates. The body cavity in

Open Mitral Valvotomy :  Technique: A median stemotomy is done; peri cardium opened and stay sutures taken. After heparinisation ascending aorta is cannulated and then SVC

Explain briefly why 'greenhouse' gases lead to global warming. The greenhouse gases do not interfere with the short-wave radiation reaching the Earth from the sun but take up t

Define working of Body surface in excretion of zinc in human? Loss of zinc occurs due to the exfoliation of skin and sweating (0.7 -1.0 mg/day). Another route of zinc loss is h

Give an example of how a functional group can affect the elements of an organic compound. The hydroxyl group on alcohols is polar and this produces alcohols polar compounds.