Ch 12Ecosystem — Class 12 Biology, concept-first.

An ecosystem is the basic functional unit of ecology -- a defined space in which a community of living organisms interacts continuously, both among themselves and with the non-living physical and chem…

Every ecosystem, regardless of its size or type, is built from two broad categories of components that continuously interact with one another: abiotic components, which are the non-living physical and…

Productivity describes the rate at which biomass, or organic matter, is generated within an ecosystem, and is one of the key functional processes -- alongside decomposition, nutrient cycling and energ…

Decomposition is the process by which the complex organic compounds present in detritus -- the dead remains of plants and animals, together with fecal matter and other organic waste -- are progressive…

Energy flow is the process by which energy enters, moves through, and is ultimately dissipated from an ecosystem, and it is one of the two defining currencies -- energy and nutrients -- that every eco…

A food chain is a straight-line sequence of organisms in which each organism feeds on, and obtains both energy and nutrients from, the organism immediately before it in the sequence, with energy being…

An ecological pyramid is a graphical way of representing the relationship between the successive trophic levels of a food chain in an ecosystem, in terms of the number of organisms present, the total…

The pyramid of numbers represents the number of individual organisms present at each trophic level of a food chain, usually counted per unit area or per unit volume of the ecosystem being studied, at…

The pyramid of biomass represents the total standing mass of living organic material -- the standing crop -- present at each trophic level of a food chain, again usually measured per unit area at a gi…

Ecological succession is the gradual, orderly, and reasonably predictable change in the species composition of a given area over time, driven by the changing environmental conditions that the organism…

Primary succession is the kind of ecological succession that begins on a substrate which has never previously supported any biological community at all -- a completely bare site with no pre-existing s…

Beyond the primary-versus-secondary distinction, ecological succession is also classified according to the moisture conditions present at the site where it begins, giving rise to two named directions…

This chapter examined the ecosystem as the basic functional unit of ecology, in which a community of living organisms interacts continuously with its physical and chemical surroundings.

Sample papers and previous-year board questions for this subject.