Zoology

A multiple birth is the culmination of one multiple pregnancy, wherein the mother delivers two or more offspring.

A transitional fossil is any fossilized remains of a life form that exhibits traits common to both an ancestral group and its derived descendant group.

Breeding back is a form of artificial selection by the deliberate selective breeding of domestic animals, in an attempt to achieve an animal breed with a phenotype that resembles a wildtype ancestor, usually one that is extinct.

A bezoar /ˈbiːzɔər/ is a mass found trapped in the gastrointestinal system, though it can occur in other locations.

In ethology, territory is the sociographical area that an animal of a particular species consistently defends against conspecifics (or, occasionally, animals of other species).

Ichthyology (from Greek: ἰχθύς, ikhthus, "fish"; and λόγος, logos, "study"), also known as fish science, is the branch of biology devoted to the study of fish.

Invertebrates are animals that neither possess nor develop a vertebral column (commonly known as a backbone or spine), derived from the notochord.

Twins are two offspring produced by the same pregnancy.

Photoperiodism is the physiological reaction of organisms to the length of day or night.

An Animal track is the imprint left behind in soil, snow, mud, or other ground surfaces that an animal walks across.

Cladistics (from Greek κλάδος, klados, i.e., "branch") is an approach to biological classification in which organisms are categorized based on shared derived characteristics that can be traced to a group's most recent common ancestor and are not present in more distant ancestors.

In evolutionary ecology, an ecotype, sometimes called ecospecies, describes a genetically distinct geographic variety, population or race within a species, which is adapted to specific environmental conditions.

In biology, moulting (British English), or molting (American English), also known as sloughing, shedding, or in many invertebrates, ecdysis, is the manner in which an animal routinely casts off a part of its body (often, but not always, an outer layer or covering), either at specific times of the year, or at specific points in its life cycle.

Bioacoustics is a cross-disciplinary science that combines biology and acoustics.

Menstruation in mammals is the shedding of the uterine lining (endometrium).

The development of the gonads is part of the prenatal development of the reproductive system and ultimately forms the testes in males and the ovaries in females.

In biology, dactyly is the arrangement of digits (fingers and toes) on the hands, feet, or sometimes wings of a tetrapod animal.

Swarm behaviour, or swarming, is a collective behaviour exhibited by entities, particularly animals, of similar size which aggregate together, perhaps milling about the same spot or perhaps moving en masse or migrating in some direction.

In animals, infanticide involves the killing of young offspring by a mature animal of its own species, and is studied in zoology, specifically in the field of ethology.

Hearing range describes the range of frequencies that can be heard by humans or other animals, though it can also refer to the range of levels.

Organisms can live at high altitude, either on land, or while flying.

In biology, sessility (in the sense of positional movement or motility) refers to organisms that do not possess a means of self-locomotion and are normally immobile.

Overpopulation occurs when a species' population exceeds the carrying capacity of its ecological niche.

Captive breeding is the process of breeding animals in controlled environments within well-defined settings, such as wildlife reserves, zoos and other commercial and noncommercial conservation facilities.