Vestigial Organs: These are those organs which occur in reduced form and are useless to the possessor but are fully developed and functional in the related animals. These organs were necessary in the ancestral forms; bur are gradually disappearing in the present say forms due to change in their mode of life. EXAMPLES:
1 Tail bone(coccyx) in human beings.
2 Third eyelid in human beings(Nictitating membrane) is highly reduced and non-functional in all of us as the cornea is cleaned by the upper eyelid. But it is well developed and functional in frog, pigeon and cat.
3 Auricular muscles are present in pinna in mammals with these muscles mammals like rabbit, dog and cow move their pinna towards the source of sound. But in case of man these muscles are reduced and non-functional.
4 Caecum and vermiform appendix: vermiform appendix is the blind tube at the end of caecum found in some mammals. In herbivores. caecum and vermiform appendix are highly developed and helps in the digestion of cellulose. But in man it is reduced and non functional.
5 The snakes have evolved from lizard like reptiles having two pairs of limbs(functional). But due to change in their mode of life, they have lost the limbs but pythons and boas still retain the hind limbs.
- Fossils of single celled prokaryotes or microfossils were found that were believed to be 3500 million year old. These were similar to those found living today.
- Fossilized remains of STROMALITES were found and provided information on the structure of early organisms. Simple bacteria existed in these structures were very similar to present day STROMALITES>
- Discovery of NANOBACTERIA were found in meteorite of mars.
In general, using fossil evidence from different rock layers it has been found that the more primitive cells and marine organisms are found in lower layers compared to the more complex and land dwelling organisms. It suggested that simple organisms precede complex organism.