1. Biotic community : An association of a number of different interrelated populations belonging to different species in common environment such as forests, a lawn or a desert track.
  2. Biotic isolation : The occurrence of organisms in isolation from others of their species.
  3. Biotic succession : Series of changes that a community undergoes until a group of its members is established i.e. live and reproduce successfully in the area. Each community in the succession is named after a plant species of bigger size or large number called dominant species which have a major influence on the total environment such as pine forest, moss community, etc.
  4. Camouflage : Colour and pattern of animals which blend with their environment so as to minimize the risk of predation.
  5. Competition : The relation which evolves struggle among different organisms for various requirements of life.
  6. Mimicry : The phenomenon in which particular harmless species of animals shows similarity to another species of animals which is dangerous, poisonous or disasterful to avoid its enemies.
  7. Parasite (s) : Organism that lives partly or fully in close association with another (host) – inside (endoparasite) or outside (ectoparasite) – draws food from the host without giving anything in return; host may or may not feel the loss or injury caused by the parasite – parasite plants including dodder Cuscuta species (total stem parasite) mistletoe Loranthus species.
  8. Parasitism : Temporary or permanent relationship between two different organisms in which only one (parasite) derives the benefit.
  9. Primary succession : An ecological succession of vegetation that occurs in passing from barren earth as water to a climax community.
  10. Scavenging : Direct food relation between two species of animals – vulture feeds on carcass of animals which have died naturally or have been killed by other animals.
  11. Secondary succession : A series of changes which continue to occur in a community until a group of organisms get established which live and reproduce most successfully in this community.
  12. Symbiosis : An association of two species of the organisms when both the patterns derive benefit from each other.
  13. Symbiosis : Association of two different organisms, wherein both derive benefit from each other – bacteria found in the root nodules of leguminous plants.