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In biology, a tropism is a phenomenon indicating the growth or turning movement of an organism, usually a plant, in response to an environmental stimulus. [1] In tropisms, this response is dependent on the direction of the stimulus (as opposed to nastic movements, which are non-directional responses).
The term tropic is from Ancient Greek τροπικός (tropikós), in the sense "of or pertaining to a turn or change", meaning "causing a change, affecting"; this is the same origin as tropic and trope. This should not be confused with trophic, as in similar-sounding trophic hormone – the words and concepts are both unrelated. [3]
Tropical ecology is the study of the relationships between the biotic and abiotic components of the tropics, or the area of the Earth that lies between the Tropic of Cancer and the Tropic of Capricorn (23.4378° N and 23.4378° S, respectively). The tropical climate experiences hot, humid weather and rainfall year-round.
The Tropic of Cancer is the Northernmost latitude from which the Sun can ever be seen directly overhead, and the Tropic of Capricorn is the Southernmost. [8] This means that the tropical zone includes everywhere on Earth which is a subsolar point at least once during the solar year. Thus the maximum latitudes of the tropics have equal distances ...
The mean trophic level of the world fisheries catch has steadily declined because many high trophic level fish, such as this tuna, have been overfished. In fisheries, the mean trophic level for the fisheries catch across an entire area or ecosystem is calculated for year y as:
Trophic cascades are powerful indirect interactions that can control entire ecosystems, occurring when a trophic level in a food web is suppressed. For example, a top-down cascade will occur if predators are effective enough in predation to reduce the abundance, or alter the behavior of their prey, thereby releasing the next lower trophic level from predation (or herbivory if the intermediate ...
The mean chain length of an entire web is the arithmetic average of the lengths of all chains in a food web. [ 42 ] [ 14 ] In a simple predator-prey example, a deer is one step removed from the plants it eats (chain length = 1) and a wolf that eats the deer is two steps removed from the plants (chain length = 2).
Ecological efficiency is a combination of several related efficiencies that describe resource utilization and the extent to which resources are converted into biomass. [1] ...