Page 5 - ln-ch-7

These are degenerate, non-functional and rudimentary organs to the possessor,
while correspond to fully developed and functional organs of related organisms.
(a) There are about 90 vestigial organs in the human body. Same of them are tail
bone (coccyx), wisdom teeth, nictitating membrane, vermiform appendix, etc.
(b) Some examples from other animals are hip girdles and bones of the hind limbs in
some whales and certain snakes and wings of flightless birds.

Biochemical Evidences
(a) The metabolic processes in organisms are similar with same new materials and
end products. For example, energy released by oxidation is stored in ATP which then
powers the energy requiring process.
(b) Molecular homology is the similarity among animals at the molecular level.
For example, human DNA differs in only 1.8% of its base pairs from chimpanzee DNA
and there is no difference between the two in the amino acid sequence for the
protein cytochrome-c.
(iv) Biogeographical evidences The species restricted to a region develop unique
features. Also, species present in far separated regions show similarity of ancestry.
This can be explained with the help of following processes:
I. Adaptive radiation is an evolutionary process in which an ancestral stock gives
rise to new species adapted to new habitats and new ways of life. Examples are (0
Darwin’s finches These were small black birds, which Darwin observed in Galapagos
island.
(a) He observed many varieties of finches in the same island.

(b) All varieties of finches had evolved from original seed-eating finches.
(c) There was alternation in beaks enabling some to become insectivorous and
some vegetarian.

(ii) Marsupials of Australia A number of marsupials, different from each other
evolved from an ancestral stock, all within the Australian island continent.
II. Parallel evolution refers to independent development of similar characters in two
animal groups of common ancestry living in similar habitats of different continents.
Examples are
Marsupial mammals in Australia show parallel evolution as they have evolved from
placental mammals. All these closely resemble and look similar to a corresponding
marsupial.
Few examples are mentioned in the table.