Q.Arrange the following in the correct ecological hierarchy: community, ecosystem, population, biome.

Ecology is the study of how organisms interact with each other and with their physical surroundings. It is traditionally split into autecology, which examines a single species in relation to its environment (its tolerance limits, feeding pattern, breeding cycle), and synecology, which examines whole groups of organisms — populations and communities — and the relationships between them.

Ecological organisation is built as a nested hierarchy, each level composed of units from the level beneath it: an individual organism belongs to a population (all interbreeding members of one species in an area), populations of different species together form a community, a community plus its physical environment forms an ecosystem, ecosystems of a similar climate and vegetation type group into a biome, and all the biomes on Earth together make up the biosphere (or ecosphere) — the global zone where life exists.

Every level in this hierarchy has properties that do not exist at the level below: a population has a birth and death rate, a community has species diversity, an ecosystem has energy flow and nutrient cycling — none of which make sense applied to a single organism alone. This is why ecologists study whole systems, not isolated individuals.

Within this framework, habitat and niche describe different things about an organism's place in nature. Habitat is simply where an organism lives — its physical address, such as a pond or a forest floor. Niche is what the organism does there — its feeding habits, activity timing, and functional role, encompassing every resource it uses and every way it interacts with other species. Two species can share an identical habitat while occupying very different niches (feeding on different food, active at different times), which is exactly what allows many species to coexist in the same physical space without one outcompeting the other. Understanding this hierarchy and the habitat/niche distinction is foundational to every later ecological topic, from population interactions to ecosystem energy flow.