Morphological and anatomical evidences of evolution, Biology

Assignment Help:

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.

Related Discussions:- Morphological and anatomical evidences of evolution

What is severity and extent of lesion in cad, What is Severity and Extent o...

What is Severity and Extent of Lesion in coronaw artery disease? Apart from the high prevalence, the other disturbing features of CAD in South Asians are the severity and exten

How to calculate glycemic index, Q. How to calculate glycemic index? If...

Q. How to calculate glycemic index? If you take a certain rood and measure the rise in blood sugar in response to the food consumed in comparison with the response to an equal

Diseases of cardiovascular and haemopoietic system, D i s e a s e s ...

D i s e a s e s of Cardiovascular and Haemopoietic System Cardiovascular system maintains circulation of blood for normal exchange of fluid, electrolytes, oxygen and nut

Which type of energy is used in photosynthesis transformed, Q. Into which t...

Q. Into which type of energy is the light used in photosynthesis transformed? The luminous energy used in the photosynthesis is transformed in to the chemical energy.

Does an increase of h+ cause the hemaglobin, Does an increase of H+ cause t...

Does an increase of H+ cause the hemaglobin oxygen binding curve to shift to the left or right? Explain.

............., notochotr is absent in the group ...........

notochotr is absent in the group ...........

Ions , how do i find an atomic structure

how do i find an atomic structure

Water cycle or hydrological cycle, Water is an essential commodity for surv...

Water is an essential commodity for survival of life on these plants. The circulation of water and moisture between living organism, atmosphere and earth is called as water cycle

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd