. Population Interaction Organisms belonging to different populations interact for food, shelter, mating or for other necessities. Interaction may be intra specific (interaction within the members of same species) or inter specific (among organisms of different species). Intra specific association is observed for all livelihood processes like feeding, territoriality, breeding and protection.
Interspecific associations or interactions can be: Neutral: where different species live together but do not affect each other. Positive: it is a symbiotic relationship in which no organism in association is harmed and either one or both may be benefitted. It is of two types – Mutualism and Commensalism. Negative: One or both of the interacting organisms will be affected as in case of competition, predation, parasitism.
The common types of interspecific inter actions are: AMENSALISM (--, ): This is the ecological interaction in which an individiual species harm another without obtaining benefit, large powerful animals harm weak animals. e.g., animals destroyed at the feet of elephants equilibrium is reached and maintained. Their growth is represented by S shaped growth curve. Biotic potential or Reproductive capacity (r) It is the maximum reproductive capacity of an organism under optimum environmental conditions.
Carrying capacity (K) The maximum number of organism that a region can support without environmental degradation is called carrying capacity. Environmental resistance Is the sum total of the environmental limiting factors, both biotic and abiotic, which together act to prevent the biotic potential of an organism from being realized. Table . Differences between r- selected and K selected species r selected species (r - Reproductive capacity) K selected species (K - Carrying capacity) Smaller sized organisms Larger sized organisms Produce many offspring Produce few offspring Mature early Late maturity with extended parental care Short life expectancy Long life expectancy Each individual reproduces only once or few times in their life time Can reproduce more than once in lifetime Only few reach adulthood Most individuals reach maximum life span Unstable environment, density independent Stable environment, density dependent XII Std Zoology Chapter XII Std Zoology Chapter Organisms and Populations