Results for “population”

electrofishing

Method of collecting fishes that uses electricity to stun them, commonly used for sampling populations during scientific surveys. Causes no permanent harm to fishes when carried out properly.

Used in 1 profile

eutrophication

Hypertrophication; process by which addition of artificial or natural substances, such as nitrates and phosphates, to a body of water increases the concentration of dissolved nutrients, this in turn stimulating the growth of aquatic plant life, especially phytoplankton, and typically resulting in depletion of dissolved oxygen. Negative effects include reductions in populations of fishes and other organisms incapable of withstanding this hypoxia.

Used in 8 profiles

heating cable

Length of flexible cable buried under the substrate in an aquarium and used to maintain constant water temperature. Also popular in planted aquaria due to the associated circulation of water within the substrate which aids in nutrient exchange between plant roots and the surrounding environment.

hybridisation

The process of crossing different species or populations of organisms in order to produce hybrids.

Used in 115 profiles

inbreeding depression

Reduced fitness in a given population or group of organisms as a result of inbreeding.

nitrate reactor

Piece of aquarium equipment that can be thought of as an anaerobic filter. Provides a means by which large enough populations of anaerobic bacteria can be maintained so that nitrates are actively removed from the water in the form of nitrogen gas, a process normally facilitated by regular partial water changes. Also known as a nitrogen filter.

Palghat Gap

Also known as the 'Palakkad Gap', a low mountain pass representing the major break in the Western Ghats mountain range. The Nilgiri Hills rise to around 1100 m AMSL north of the gap and the Anaimalai Hills approximately 2000 m AMSL to the south, with average elevation within the gap 144 m AMSL. The gap has been shown to represent a biogeographic barrier restricting gene flow between populations of numerous species including Indian elephant and various birds.

Used in 1 profile

pecking order

Type of social hierarchy in which individuals within a given group or population are ranked by behavioural and/or physical dominance. Sometimes referred to as a dominance hierarchy.

Used in 106 profiles

planktonic bloom

A visble population explosion in plankton, typically involving phytoplankton, and normally resulting from an increase or excess of available nutrients.

race

Genealogical line or lineage. Sometimes used as an infrasubspecific category, i.e., below the subspecies level, to refer to populations or individuals which are not given taxonomic names.

Used in 1 profile

sex ratio

The ratio of males to females in a given population. Often used to describe the same ratio in a batch of captive-bred fishes.

Used in 5 profiles

species

Taxonomic rank into which a genus is divided, but otherwise difficult to delineate precisely with a single definition satisfying all eventualities still lacking to date. There exist a number of concepts of which the most popular in vertebrate taxonomy include the biological species concept and phylogenetic species concept.

Used in 1,790 profiles

vicariance

Separation or division of a population by a geographic barrier, such as a mountain or body of water, resulting in evolution into new varieties or species.

vicariant

Used in reference to any of several closely related species, variants, etc., each of which exists in a distinct geographical area but are assumed to have originated from a single population that became dispersed by geological events; of or relating to such an event.

wet/dry filter

Type of filter normally placed under the aquarium, and often home-made. The basic premise is that water trickles vertically downards through separated compartments containing mechanical and biological filter media with spaces inbetween so that it is also exposed to the air briefly. It then collects in a base chamber or sump from where it is pumped back to the main aquarium. There are many commercial designs available, some of which are more effective than others. Not popular in marine reef aquaria due to the associated accumulation of nitrates as by-product.