Evidence of organic evolution in life forms
– Fossil record (palaentology); - Fossils are remains of organisms that existed long time ago that have been preserved in plant resins and sedimentary rocks
; - These remains include bones, artfoets and teeth, cellulose cell walls in plants;
- Fossils are important because:-
i. They show an evidence of the type of organisms that existed long time ago
ii. They show gradual change from one form to another over long periods of time. iii. They show evolutionary relationship between organisms. iv. Fossils have been used to construct evolutionary history of organism’s like human beings, horseComparative anatomy;
- It involves comparison of the internal structures of various organisms. - Those organisms with similar structures are believed to share a common origin. The structure can be grouped into;
i. Homologous structures – these are structures with common embryonic origin but modified within the course of evolution to perform different functions due to adaptation of the organisms to different habitats leading to divergent evolution or adaptive radiation ;examples pentadactyl limbs in vertebrates. Beaks in birds.
ii. Analogous structures; – these are structures with different embryonic origin but have been modified within the course of evolution to perform similar functions due to adaptation and exploitation of the same ecological niche. This type of evolution is called convergent evolution; examples:- wings in birds and wings in insects – Those of birds originate from endoskeleton while those of insects from exoskeleton but they perform same functions of flight. Eye in human being and that of Octopus.
iii. Vestigial organ structures – reduced in size and have become functionless in course of evolution but were functional in ancestral forms e.g. reduced wings in Kiwi bird, Appendix, Coccyx in human beings.
lydiajane74 answered the question on October 27, 2017 at 10:09
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