Ecology and Environment

Vertical distribution of different species occupying different levels is called stratification. For example, trees occupy the top vertical strata or layer of a forest, shrubs occupy the second and herbs and grasses occupy the bottom layers.

The humus is further degraded humification, by some microbes and release of inorganic nutrients occur by the process known as mineralisation.

The entire sequence of communities that successively change in a given area is called sere.

The habitat plus the niche is called the ecotope, which is defined as the full range of environmental and biological variables affecting an entire species.

Sea otters (Enhydra lutris) are commonly cited as an example of a keystone species because they limit the density of sea urchins.

Arthur Tansley, a British ecologist, was the first person to use the term ecosystem in a published work.

Some soil bacteria use organic nitrogen-containing compounds as a source of carbon, and release ammonium ions into the soil. This process is known as nitrogen mineralization.

Decomposers are heterotrophic organisms, mainlyfungi and bacteria. They meet their energy and nutrient requirements by degrading dead organic matter or detritus. Decomposers secrete digestive enzymes that breakdown dead and waste materials into simple, inorganic materials, which are subsequently absorbed by them. In terrestrial ecosystems roughly 90% of the net primary production ends up being broken down by them.

Marine ecosystems generate 32% of the world's net primary production.

The Pleistocene is the geological epoch,  which lasted from about 2,588,000 to 11,700 years ago, spanning the world's recent period of repeated glaciations. Methane production in eastern Siberian lakes is controlled by organic matter,  which accumulated during the Pleistocene.

The speed with which an ecosystem returns to its initial state after disturbance is called its resilience.

Ponds that dry up completely each year are often known as vernal pools.

Faster moving water, for example streams and rivers, are Lotic.

Lake ecosystems can be divided into zones. One common system divides lakes into three zones. First is the littoral zone. It is the shallow zone near the shore. This is where rooted wetland plants occur.

The demersal zone is the part of the sea/ocean/deep lake comprising the water column that is near to the seabed and the benthos. The demersal zone is just above the benthic zone and forms a layer of the larger profundal zone.

Polar deserts such as McMurdo Dry Valleys remain ice-free because of the dry katabatic winds that flow downhill from the surrounding mountains.