CBSE Class 12-science Answered

(i) Mutualism: It is a positive interaction in which both the interacting species favour the growth and survival of each other. It is of two types:

(1) Protocooperation, in which both the species are mutually beneficial but association is facultative so that the partners can live separately.

Example: Hermit crab and sea anemone association

(2) Symbiosis, in which both the species are mutually beneficial but the association is obligatory.

Example: Lichens, a symbiotic relationship of fungus with alga

(ii) Competition: It is a type of interaction in which both the interacting species decrease the chances of growth and survival of each other as these compete for common resources.

Example: Visiting flamingos and resident fish compete for zooplankton in the lakes of South America

(iii) Predation: It is a type of interaction in which larger species (predator) attacks smaller species (prey) and kills for food. Example: All carnivorous animals are predators.

(iv) Parasitism: It is a type of interaction in which smaller species (parasite) is benefitted, but the larger species (host) is harmed. Different types of parasites include ectoparasites (lice, bed bugs), endoparasites (malarial parasite), holoparasites (Cuscuta), partial parasites and brood parasites (cuckoo).