References of classification of organisms are available in Upanishads and Vedas (1500 B.C. to 600 B.C.). However, earliest human activity can be traced back to early, middle and late stone age (400,000 B.C. – 200,000 B.C.).
About 740 plants and 250 animals have been mentioned in Vedic literature. Few significant references in old literature are,
(1) Chandyogya Upanishad : Here the animals have been classified into three categories –
(i) Jiraja (Viviparous) e.g. mammals.
(ii) Andaja (Oviparous) e.g. birds, reptiles, insects and worms.
(iii) Ubhija (Vegetal origin) e.g. small animals.
(2) Susruta Samhita (600 B.C.) : Here organisms were classified into,
(i) Sthavara in which immobile organisms like plants were kept.
(ii) Jangama in which mobile organisms like animals were placed.