The parts of the earth the different strata of air, soil and water, where living organisms survive of live together with the abiotic component is called the biosphere, and it is a global ecosystem comprised of both biotic and the abiotic(non-living) factors from which they obtain energy and nutrients

The type of natural environment in which a particular species of organism lives is termed as habitat and every organism has specific habitat needs for the situations in which it will thrive, but some are receptive to wide variations while others are very particular in their requirements. A habitat is not certainly a geographical area, it can be the inside of a stem, a rock, a rotten log or a clump of moss, and for a parasite, the habitat is the body of the host.

A niche refers to the way in which an organism fits into an ecosystem. Through the means of natural selection, a niche is the evolutionary outcome of a species physiological, morphological, and behavioural adaptations to its surroundings. The ecological niche explains how a population reacts to the allocation of resources and competitors.

Lichen is an example of mutualism type of population interactions in which both get the benefit, and it is a stable symbiotic association between a fungus and algae. The combined life form has attributes that are very distinct from the attributes of its component organisms. Lichens come in many sizes, colours and forms. The features are seldom plant-like, but lichens are not plants.

Mycorrhiza may be defined as an association of a fungus with the roots of higher flowering plants. In this case the fungi absorbs essential nutrients from the soil and provides it to the plants, While the plant provides energy yielding carbohydrates to the fungi. Here both the interacting species gets benefit and it shows mutualism interaction.