Every organism is surrounded by a host of abiotic and biotic components of the environment with which it continuously interacts. Ecology invariably studies the interactions among organisms and between the organism and its abiotic environment.
It is studied at four levels of biological organisation. The abiotic environment never remains constant all year round. All places on earth experience different seasons due to the tilt in the earth’s axis and its revolution around the sun. Annual variations in temperature and precipitation are responsible for the formation of major biomes such as deserts, rainforests and the tundra. The climate in the rainforests is so amicable that they are inhabited by nearly 40-75 percent of the world’s species. In India too, we find major biomes such as deserts, tropical rainforests, deciduous forests and coasts. Apart from climatic changes, each biome is also affected by local and regional variations, which have resulted in the formation of a wide range of habitats. Some of these habitats are favourable, while others are harsh. Life exists in all these habitats regardless of whether they are favourable or harsh. The difference in chemical and physical conditions of these habitats is due to the variation in abiotic factors such as temperature, water, light and soil.
Apart from interacting with abiotic factors, the organisms also interact with the other living organisms in their habitats such as pathogens, competitors, parasites and predators. This is the reason why organisms differ from habitat to habitat. It is assumed that organisms have evolved or modified themselves over time through natural selection to survive and reproduce in their respective habitats. Desert plants have developed special mechanisms such as spongy stems, which aid in storing water. The leaves, too, are reduced to tiny, pointed spines, which decrease the loss of water due to transpiration. Likewise, the camel has adapted itself to survive without water for 10 days at a stretch. In this way, every organism slowly adapts to the physico-chemical conditions of its habitat as well as its biotic components, to survive and reproduce.