Interactions among Organisms

1. Competition
Occurs frequently between many species. Plants vie with other plants for air, soil, water, light, and space. Different animals may need the same food, water, or space. More or less intense depending on conditions. One species wins, one may die, or each adapts.

2. Symbiosis

Symbiosis means different organisms living together in close association. The major kinds of symbiosis relationship include commensalism, mutualism and parasitism.

a) Commensalism
Commensalism is a symbiotic relationship that benefits one species and neither hurts nor helps the other. For example, epiphytes are plants that grow on the branches of other plants. In general, the host plant is unharmed, while the epiphyte that grows on it benefits.

b)Mutualism
Mutualism is a symbiotic relationship among organisms in which both species benefit. Example involves ants and aphids. Aphids also called greenflies are small insects that suck fluids from the phloem of living plants with their piercing mouthparts. They extract a certain amount of nutrients but they excrete much of it in an altered form through their anus. The ants carry the aphids to new plants, and the aphids excretion consume as the food for ants.

c) Parasitism
Parasitism may be regarded as a special form of symbiosis in which parasite or predator is much smaller than the prey. Parasitism is harmful to the prey organism and beneficial to the parasite. In parasitism, one organism serves as a host to another organism and usually to the host’s disadvantage. Flea bites on a human is an example of parasitism (the flea as parasite to the human host in this case).


3. saprophyte

Is the organism that feeds on dead or decaying tissues of other organisms. It is in the class of detrivores. In food webs, detritivores generally play the role of decomposers. Detritivores are often eaten by consumers and therefore commonly play important roles as recyclers in ecosystem.