PHYSIOLOGY AND BIOCHEMISTRY -

• Ample and concrete evidence of organic evolution are obtained from the functional activity and chemical composition of animals.
• J.B.S. Haldane (1937) stated that final theory of evolution will see it largely as a biochemical process.
• Protoplasm - Protoplasm is a physical basis of life. Each cell is composed of a colloidal substance called protoplasm. The chemical composition of protoplasm is fundamentally similar in all animals.
• Chromosome - Chromosomes are common to all living cells. They have the same chemical composition in all animals. Each chromosome is formed of proteins and nucleic acids. This is because of a common ancestry.
• DNA - In all animals DNA functions 'as the genetic material. It is formed of many small units called nucleotides.
• Each nucleotide has similar bases and attachment in all organisms.
• Chimpanzees and humans share more than 97 percent of their genes.
• Some genetic differences of vertebrates as estimated by DNA hybridization are as follows -

Organisms                                                % of difference in DNA sequences

Human/Chimpanzee                                                  1.6

Human/Gibbon                                                         3.6

Human/Rhesus monkey                                              5.5

• Thus it can be concluded that closest living relative of man is chimpanzee. It can be proved by antiserum test.
• Enzymes - Enzymes are proteins of high molecular weight necessary for the digestion of food. Trypsin is a protein has the same structure and function form protozoa to man. Similar amylase splits starch and occurs from the sponge to man. The similarity of enzymes shows interrelationship between various animals.
• Hormones - Hormones are chemical messengers secreted by the endocrine glands. Thyroxine secreted by vertebrates is similar in their structure and function. In frog it is essential for metamorphosis. Thyroxine deficiency in man can be treated with the thyroxine hormone of other animals.