Ecology Lecture Notes

Biological Interactions: Positive and Negative Interactions in an Ecosystem (.PPT)


ecological interactions

Organisms living together in a community influence each other directly or indirectly under natural conditions. All the vital process of living such as growth, nutrition and reproduction requires such interactions between individuals in the same species (intraspecific) or between species (interspecific) These inter or intra relationships of individuals in a population or community of an ecosystem is called biological interactions or population interactions. The interaction between organisms may not be always beneficial to all the interacting counter parts. Based on whether, the interaction is beneficial to both interacting species or harmful to at least one interaction species, the ecological of biological interactions are classified into two categories.

(I).   Positive interactions

(II). Negative interactions

(I). Positive interactions:

In positive interactions, the interacting populations help one another. The positive interaction may be in one way or reciprocal. The benefit may be in respect of food, shelter, substratum or transportation. The positive association may be continuous, transitory, obligate or facultative. The two interacting partners may be in close contact in such a way that the tissues intermixed with each other; or they may live within a specific area of the other; or attached to its surface.  Different types of positive population interactions are:

(1). Mutualism

(2). Commensalism

(3). Proto-cooperation

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