Thursday 30 April 2020
Discuss the various evidences of organic evolution
Comparative anatomy/taxonomy; members of a
phylum/group show similarities; organs have similar structure/organs performing
the same function such as the digestive system, urinary system, vertebrate
heart; homologous structures are structures with the same embryonic origin but
have been modified to perform different and specific functions; show a form of
divergent evolution; e.g. the pentadactyl limb in vertebrates which has been
modified for racing; swimming and flight or beaks of finches and birds; while
analogous structures are those with different embryonic origin but have been
modified to perform the same function e.g. wings of insects, bats and birds;
eyes in octopuses and humans; show a form of convergent evolution; vestigial
structures; have been reduced in size and become functionless; in the course of
evolution; e.g. limbs in snakes, human hair and tail; Cell biology/cytology;
occurrence of similar organelles such as the mitochondria and the endoplasmic
reticula point to common ancestry; Fossil records/Paleontology; remains of
organisms preserved in naturally-occurring materials for many years; fossil
records show morphological changes of organisms over a long period of time e.g.
skull of humans and horse; they provide a direct evidence of existence of
organisms at a particular ecological era; however, since only hard parts are
preserved, no evidence is available for existence of soft-bodied organisms; and
there are many missing links; since remains are accidentally preserved in
rudimentary rocks and resins; Comparative embryology; vertebrate embryos are
morphologically similar during the early stages of development; suggesting that
the organisms had a common ancestry/origin e.g. larvae of mollusks/annelids,
embryos of chicken, humans, sheep; the closer the semblance between embryos,
the closer their ancestral backgrounds; Geographical distribution; present
continents are thought to have been a large land mass joined together; as a result
of continental drift; isolation occurred bringing about different patterns of
evolution; where plants and animals from different continents yet with common
ancestry can no longer interbreed; because they evolved into different species;
examples of animals that moved to different areas are the jaguars and Llamas in
south America, lions in Africa, Tigers in Asia, marsupials in Australia;
Comparative serology/physiology; semblance in blood components such as blood
proteins, antigen-antibody reactions, structure of haemoglobin in all
vertebrates; reveal some phylogenic relationship among organisms/show common
ancestry;
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