Evidences from physiology and biochemistry

Biochemical similarity

In all organisms the basic molecules of cell are the same, e.g. carbohydrates, amino acids, lipids, nucleic acids, enzymes, etc.

The nitrogen bases, the nucleotides, are the same for all organisms, only the length and sequence may vary.

Content of matrix (including plasma) are similar for all the vertebrates Metabolic process of cell are same in all organism. e.g. glycolysis, Kreb’s cycle, oxidative phosphorylation and others. The genetic code and the mechanism of protein synthesis are also similar in all organisms.

Trypsin, the oldest known enzyme (ancestral enzyme) is found in all animals from Protozoa to Primates.

Serological similarities :

In blood plasma contents, antibodies, cell types (RBC, WBC) hemoglobin all are similar. Hormones are of similar types hence, extracts from one induces same effect in other.