Ecology [BR]The word comes from Greek word Oikos which means household. It is the branch of biology concerned with the relations between organisms and their environment (land, air, water, light, heat). A food chain is a sequence of organisms organized by food, for example: a plant is eaten by insects, which are food for frogs that are eaten by snakes, these are falcon’s food, and to conclude the food chain all those animals when they die are microorganism’s food. The food chain is divided in producers, consumers and decomposers. Habitat is a specific place or natural conditions in which a plant or animal lives. A microhabitat or microenvironment is the immediate surroundings and other physical factors of an individual plant or animal within its habitat. An ecosystem can be defined as a natural unit consisting of all plants, animals and micro-organisms in an area functioning together with all of the non-living physical factors of the environment. Positive ecological interactions are: society, mutualism, commensalisms, symbiosis and colony. Negative ecological interactions are: competition, predation and parasitism.