Glossary: A

"Arthropod" eyes

Eye composed of ommatidia (singular, ommatidium). Synapomorphy of the Arthropoda.

Allee effect

A situation where the density of an animal population is so low as to cause adverse effects on the population. For example, adult animals may have trouble finding other adults to mate with because they are so scarce.

Antarctic convergence

The region between 50 to 55 degrees south where the Antarctic surface water sinks beneath the less dense and southward flowing subantarctic water.

Antarctica

lives on Antarctica, the southernmost continent which sits astride the southern pole.

Arctic Ocean

the body of water between Europe, Asia, and North America which occurs mostly north of the Arctic circle.

Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

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Australian

Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.

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abiotic

something that was never alive, such as water or rocks. This term is often used to refer to the physical environment.

aboral

On the side of the body opposite the mouth.

abyssal

on or near the ocean floor in the deep ocean. Abyssal regions are characterized by complete lack of light, extremely high water pressure, low nutrient availability, and continuous cold (3 degrees C).

acoelomate

lacking a coelom (body cavity lined with mesoderm)

acoustic

uses sound to communicate

adhesion

sticking to a surface

adult

A fully developed and mature animal, physically capable of breeding, but not necessarily doing so until social and/or ecological conditions allow.

aerobic

Deriving energy from a process requiring free oxygen (compare anaerobic).

aestivate

To enter a state of dormancy in seasonal hot, dry weather, when food is scarce. Sometimes spelled "estivate."

agonistic

Referring to behavior between individuals of the same species that may involve aggression, threat, appeasement or avoidance. Agonistic behavior may arise from a conflict between aggression and fear.

agricultural

living in landscapes dominated by human agriculture.

allele

One of the forms of a given gene.

alloparent

An animal behaving parentally towards infants or young that are not its own offspring.

allopatric

Referring to a situation in which populations of different species are geographically separated (compare Sympatric).

alluvial

referring to soil which has been deposited by running water.

alpha diversity

See diversity - alpha.

alpine

Referring to conditions similar to those found in the Alps or other higher mountains (usually above 1500 m (4900')) .

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

See Also: precocial
ambulacral

those areas of an echinoderms body that bear tube feet

ambulacral grooves

radial grooves along which tube feet project to the exterior of the organism.

amniotic egg

An egg protected by a series of membranes: the amnion, which surrounds the embryo with a constant amniotic fluid environment; the allantois, which allows gas diffusion and waste removal; the yolk sac, providing a food source for the embryo; and the chorion, a protective layer around the entire egg. Synapomorphy of the Amniota.

amoebocyte

an animal cell without a fixed position in the body, they are able to wander throughout the body and feed on foreign particles, such as invading bacteria. Examples are leucocytes in mammalian blood.

amphibious

Able to live both on land and in the water.

amphidromous

Referring to fish that migrate between fresh and salt water, but not as part of their life cycle. Migrations usually occur for short periods of feeding, and amphidromy is common among fishes that inhabit islands.

ampullae

the enlarged end of a tube or canal, used to refer to the enlarged ends of echinoderm tube feet, an enlargement at the end of the semicircular canals of the inner ear of vertebrates, or, more generally, the dilated end of a vessel or duct.

anadromous

Referring to fish that live primarily in salt water but migrate to fresh water to reproduce. Most of the growth takes place in oceans and no significant feeding occurs when spawning migration commences.

See Also: catadromous
anaerobic

Deriving energy from a process that does not require free oxygen (compare aerobic).

anterior

describing the part of an animal, or position of a structure, that is oriented towards the front in normal locomotion.

anti-predator behavior

actions an organism takes to keep predators from eating it.

aposematic

having coloration that serves a protective function for the animal, usually used to refer to animals with colors that warn predators of their toxicity. For example: animals with bright red or yellow coloration are often toxic or distasteful.

having colors that act to protect the animal, often from predators. For example: animals that are bright red or yellow are often toxic or distasteful, their colors discourage predators from eating them.

appendage

body part that sticks out, like a leg or toe or antenna

aquatic

Living mainly in the water.

aquatic biomes

major categories of aquatic habitats, such as coastal, pelagic, or benthic regions, etc.

arachnid

a species in a class of arthropods which includes mostly air-breathing invertebrates, including spiders, scorpions, mites and ticks. Arachnids have a body with two segments, with the front segment having four pairs of legs and no antennae.

arboreal

Referring to an animal that lives in trees; tree-climbing.

archeocyte

an amoeboid cell type found in sponges which can differentiate into several other, specialized cells, including sclerocytes, which secrete spicules, spongocytes, which secret spongin fibers, and collencytes, which secrete fibrillar collagen. Archeocytes can also ingest particles through phagocytosis.

archipelago

A group of islands.

arid

a climate or habitat characterized by little precipitation, by evaporation exceeding precipitation, and by sparse vegetation.

a climate or habitat which gets little rainfall, resulting in sparse vegetation. Examples are deserts, chaparral, and scrub forests. Arid generally means dry.

armor

protective body covering that is used to protect an animal from predation. For example, a snail's shell or an armadillo's protective plates.

arthropod

Referring to an insect, spider, crab or other member of a species with a hard, jointed exoskeleton and paired, jointed legs.

articulate

in bones, coming together or touching

artiodactyl

Referring to an even-toed ungulate (includes the cattle, pigs and ruminants).

asexual

reproduction that is not sexual; that is, reproduction that does not include recombining the genotypes of two parents

attachment stage

the stage in an animal's lifecycle when they cease being motile and become attached to a substrate.

auricularia larva

the larvae of members of the class Holothuroidea, sea cucumbers.

autotomize

a process whereby an animal sheds a body part, such as the tail in lizards. Autotomy is followed by regeneration of the body part. It often serves as a protective function, losing the body part to escape predation rather than being eaten, but is also a form of asexual reproduction in polychaete worms.

autotomy

an adaptation that makes it possible for an animal to rapidly lose an appendage, such as a tail or leg, in order to elude a predator's grasp by sacrificing a non-essential body part. The lost appendage is often re-grown.