Study of the functional aspects of the organism is called physiology. The organs and organ systems are similar in the closely related animals. The functional aspect of closely related animals is also same. The physiological evidences are studied in three headings;
1. FUNDAMENTAL UNITY OF LIFE,
2,BIOCHEMICAL SIMILARITIES BETWEEN GROUPS and
3, BIOCHEMICAL RECAPITULATIONS.
1. FUNDAMENTAL UNITY OF LIFE
The functional units of all living organisms are cells. This similarity indicates that the different animals have relationship. Every cell contains all kinds of cell organelles Golgicomplex, E.R. Lysosomes, Mitochondria, Chromosomes,D.N.A and R.N.A). In all the living organisms mitochondria are for energry production and storage. D.N.A is the hereditary material in all the living organisms. Ribosomes perform protein synthesis in all the living organisms.
2. BIOCHEMICAL SIMILARITIES BETWEEN GROUPS
The different types of biochemical reactions occur in every living organism. These reactions are same in all the living organisms. Some of the chemicals and their reactions are
The amylase in all the living organisms digests the carbohydrates.
The trypsin in all the living organisms digests the proteins.
In Frog, the metamorphosing hormone is thyroxin. If human thyroxin is injected into thyroid free tadpole larva, it undergoes metamorphosis. This indicates that the function of thyroxin is same in all animals.
It carries oxygen and carbon dioxide in all animals. Hemoglobin carries oxygen in the form of oxyhemoglobin. In all birds the oxyhemoglobin is identical. This indicates that the birds have close relationship among themselves.
D. Blood precipitation tests:
These are the antigen antibody reactions. Nuttal used the rabbit for the synthesis of anti bodies. To know the relationship of man with other animals, scientists first injected small amount of human blood into the rabbit. As our blood is a foreign material to rabbit, our blood stimulates the production of antibodies in rabbit. Collect serum from such rabbit. That serum is called anti human serum. It is poured Into blood of anthropoid ape, monkey, dog.
The blood of anthropoid ape with in short time is changed into large amount of precipitate than the amount of precipitate in the blood of monkey and dog. It indicates that the anthropoid ape is close relative to man than monkey and dog.
Blood precipitation tests are also revealed that the Siren and Necturus are close relatives to crypto bronchus.
Blood precipitation tests are also revealed that the Bandicoots are close relatives to mice.
The bonefishes excrete ammonia. The tad pole larva of Frog excretes ammonia to recapitulate the excretory product of fishes.
Birds embryo first ‘4’ days excretes ammonia like fishes, then nine days excretes urea like amphibians and finally excretes uric acid like reptiles and birds. This sequence of elimination of excretory products by birds embryo explains the recapitulation of their ancestral excretory products.
The mammals embryo first excretes ammonia, then urea, then uric acid and finally urea. This is to recapitulate the excretory materials of their ancestors, fishes, amphibians and reptiles serially before excreting urea.
more details about Embryological evidence of Evolution