(i) Free living: Animals that move freely. For example – pigeon, cow
(ii) Parasite: Those organisms which live in the body of another organism and take food from it are called parasites. For example, worms, lice etc. (iii) Symbiont: When two different species live together and benefit both, it is called symbiont. For example – Chlorohydra viridissima and Zoochlorella.
(iv) Commensal: Two different species of organisms living together are called symbionts, neither benefiting nor being harmed by the other. For example, the sucking fish called Remora shows symbiosis by attaching to the body of Shark or any other fish.