Zoology Glossary ~ B

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Balanced Polymorphisim
The maintenance of more than one allele in a population due to the superiority (in selection terms) of the heterozygote over both homozygotes.

Baleen
A fibrous structure in the mouths of some whales (baleen whales or Mysticetes) that enables the whale to filter food from the water for ingestion.

Banding
The practice of attaching metal or plastic bands around the legs of birds (or other animals) to mark individuals for identification on recapture.

Barbel
A long tubercle (projection) that serves as a sensory appendage and is attached to an animal's lips or mouthparts.

Barbicels
Small hook-like structures on barbules that link adjoining barbules to form the rigid, interlocked structure of the feather vane.

Barbs
The structures that branch from the main shaft of a feather and form the feather's vanes.

Barbules
Small structures that grow from the barbs of a bird's feather. Barbules overlap and interlock to give a feather rigidity.

Barren
Characterized by sparse vegetation due to limitations in the physical environment (such as a harsh climate or the chemical properties of the soil).

Basal
Relating to, located at, or forming the base.

Basic Plumage
If a bird species only molts once a year, their basic plummge is the set of feathers they have throughout the year. If a bird species experiences two molts per year, the basic plumage is (in most cases) the plumage grown after a complete molt and is present during the bird's nonbreeding season.

Batesian Mimicry
The resemblance between a mimic species (which is not harmful or unpaletable if ingested) and a model species (which is harmful or unpaletable if ingested).

Beak
Narrow, protruding jaws that usually do not contain teeth. Present in various groups of vertebrates including some cetaceans.

Benthic
Associated with the bottoms of rivers, lakes, and oceans. Bottom-dwelling.

Beta Diversity
A measure of the variety of organisms in a region. Beta diversity is influenced by the turnover of species among habitats.

Bilateral Symmetry
A type of symmetry in which an organism's body possesses two equal halves that are symmetrical when compared on either side of a midline. Most animals exhibit bilateral symmetry.

Bill
A bird's jaws which consist of bone and a hornlike outer layer of keratin.

Binocular Vision
A type of vision in which an animals two eyes face forward providing overlapping fields of view that enable the animal to judge depth.

Biodiversity
A measure of the variety of organisms in a habitat or ecosystem. Can be measured by the number of species or genetic variation in an area or ecosystem.

Biogeography
The study of the geographic distribution of organisms throughout the landscape. Examines the how geographical variation in the physical environment manifests variation in the biotic components that inhabit the area.

Biomass
The weight of living material (expressed as a dry weight) in some unit such as an organism, population, or community. Biomass is often cited as weight per unit area (biomass density).

Biome
A distinct group lifeforms and the environment in which they are found.

Biota
The living components (fauna and flora) of an ecosystem or habitat.

Birth Rate
The average number of offspring produced per individual per unit of time. Birth rate is often expressed as a function of age.

Blowhole
A hole on top of a cetacean's head through which air is inhaled and exhaled. The blowhole is found on top of the head so as to prevent water from flowing into the lungs.

Boreal
Referring to the coniferous forest regions that extend throughout areas of North America (Canada), Europe and Asia.

Boundary Layer
A layer of slow-moving water or air that lies just above the surface of an object.

Bow Riding
The behavior of cetaceans (commonly dolphins) in which they swim or 'ride' the crests of ocean waves.

Breeding System
The type of breeding behaviors characteristic of a population (polygyny, outcrossing, or selective mating) and the ways in which members of the population adapt to these breeding behaviors.

Brilles
Transparent layers that cover the eyes of all snakes and some lizards. Brilles cannot be moved (in contrast to lids).

Bristles
Long, stiff feathers that are often found near a bird's mouth or eyes. The function of bristles is not well-understood and it is thought they may serve to funnel food into a bird's mouth or provide protection to the bird's eyes.

Broken Stick Model
A model that describes the relative abundance of species by random segmentization of a line representing the resources of the environment.

Brood Parasite
A bird that lays its eggs in the nest of another bird (either another species or another individual of the same species) so that the young will be raised by the host parents.

Brood Parasitism
A method of reproduction seen in birds that involves the laying of eggs in the nests of other birds. The eggs are left under the parantal care of the host parents.

Brood Patch
An area that develops on the lower abdomen of birds in which the feathers drop off and the skin thickens and becomes densely populated with blood vessels. Used in incubation to keep eggs and young warm.

Brood Reduction
A reproductive strategy in which a female bird produces more eggs than she would normally be capable of raising.

Brooding
A behavior in birds in which the parents continue to warm nestlings or young that are unable to maintain their own body temperatures.