Animal Info - Glossary E

Echolocation

The process by which an animal locates itself with respect to other animals and objects by emitting sound waves and sensing the pattern of the reflected sound waves.

Ecological density

Ecological (or "specific") density is the number (or biomass) per unit of habitat space (available area or volume that can actually be colonized by the population) (see "Crude density").

Ecological extinction

The reduction of a species to such low abundance that, although it is still present in the community, it no longer interacts significantly with other species.

Ecology

The study of the interrelationships among plants, animals and other organisms and their interaction with all aspects of their natural environmental.

Ecosystem

1. "...the more fundamental conception is ... the whole system ..., including not only the organism-complex, but also the whole complex of physical factors forming what we call the environment of the biome - the habitat factors in the widest sense.

It is the systems so formed which, from the point of view of the ecologist, are the basic units of nature on the face of the earth.

These ecosystems, as we may call them, are of the most various kinds and sizes..."

(Introduction and definition of a new term, "ecosystem," by Alfred Tansley in 1935)

2. All the individuals, species and populations in a spatially defined area, the interactions among them, and those between the organisms and the abiotic environment.

Ecosystem functioning

The sum total of processes operating at the ecosystem level, such as the cycling of matter, energy and nutrients, as well as those processes operating at lower ecological levels which impact on patterns or processes at the ecosystem level (e.g. interactions among species or the transfer of genetic material).

Ecotone

A transition between two or more different habitats; e.g. between forest and grassland.

Ecotype

A genetically induced variety within a single species, adapted for local ecological conditions.

Edentate

A member of an order comprising living and extinct anteaters, armadillos, pangolins and sloths.

Edaphic

Influenced by the soil rather than the climate.

Effective population size

The average number of individuals in a population that actually contribute genes to succeeding generations. This number is generally lower than the observed, censused population size, being reduced by the following factors: 1) a higher proportion of one sex may mate; 2) some individuals will pass on more genes by having more offspring in a lifetime than others; 3) any severe past reduction in population size may result in the random loss of one or more particular genes. (Allaby 1991)

Embryonic diapause

In some species (e.g. in most kangaroo species), at about the time a female gives birth, she also becomes receptive and mates. Embryos produced at this mating develop only as far as a hollow ball of cells (the blastocyst) and then become quiescent, entering a state of suspended animation or "embryonic diapause." The hormonal signal (prolactin) which blocks further development of the blastocyst is produced in response to the sucking stimulus from the young in the pouch. When sucking decreases as the young begins to eat other food and to leave the pouch, or if the young is lost from the pouch, the quiescent blastocyst resumes development, the embryo is born, and the cycle begins again. (Macdonald 1984)

Endemic

A species is "endemic" to a particular area if it occurs naturally only in that area. The term is usually applied to a species with a very limited range, or a species that only occurs in one country.

Enzootic

A disease that is persistently found in an animal population (compare "Epizootic").

Ephemeral

Short-lived, or of brief duration.

Epiphytic

Referring to a plant that lives on the surface of another plant and obtains its moisture and nutrients from the air and rain.

Epizootic

A disease outbreak in an animal population that occurs at a particular time and does not persist (compare "Enzootic").

Equids

A term collectively referring to asses, horses and zebras.

Erg

An Arabic term for the great sand deserts, or sand "seas", of the Sahara Desert (actually, the term erg in Arabic means "a vein or belt"). An erg can be as large as France, covering well over 260,000 sq km (100,000 sq mi). An erg consists mostly of sand, shaped by the wind into dunes, and it may contain salt flats and the exposed gravel surface of the desert floor. (Langewiesche 1996)

Escarpment

A long cliff separating two relatively level or gently sloping surfaces.

Estrus (adjective: "estrous")

The period in the estrous cycle of a female mammal when she is usually attractive to males and receptive to mating.

Estrous cycle

In female mammals (other than most primates), the hormonally controlled, regularly repeated stages by which the body is prepared for reproduction.

Estuary

An arm of the sea at the mouth of a river. Usually an estuary is characterized by a two-layer flow, where the top layer consists of fresh water flowing downstream and the bottom layer consists of salt water flowing upstream from the sea.

Etymology

The history of a word shown by tracing its development from another language.

Eurythermic

Referring to an animal that can tolerate a wide range of temperatures ("eury-" = "broad" or "wide").

Exoskeleton

A hard supporting structure on the outside of the body, enclosing all living cells ("external skeleton").

Exotic species

Introduced, non-native species.

Extirpate

To wipe out.

Exudate

A material that has oozed out of something. For example, gum that has oozed out of a tree through a wound in the bark.

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