Zoology Glossary ~ D

Zoology Glossary Index:
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Dabble
A behavior in birds that involves reaching the bill into shallow water to forage for food. This behavior does not involve diving or leaving the surface of the water.

Death Rate
The percentage of newborn dying during a specified interval.

Definitive Plumage
The mature plumage of a bird attained after the molting of all immature plumages. Definitive plumage does not change as the bird ages and is renewed after each molt with identically marked
plumage.

Delayed Plumage Maturation
The delayed development of a bird's definitive plumage such that the bird reaches sexual maturity before its replaces its immature plumage has been relaced. Occurs more frequently in the males of a species.

Delist
To remove an animal or plant species from the list of endangered and threatened wildlife and plants.

Delphinidae
A taxonomic group of marine mammals that includes dolphins and their relatives. The delphinidae, or Family Delphinidae, belong to the Order Cetacea and is the most diverse of all groups of cetaceans.

Deme
A breeding population or local population that occurs in nature and which consists of similar organisms that interbreed more or less at random.

Demographic
A characteristic used to describe some aspect of a population and that can be measured for that population, such as growth rate, age structure, birth rate, and gross reproduction rate.

Density Compensation
Increase in population size in response to reduction in the nubmer of competing populations; often observed on islands.

Density Dependent
Having influence on individuals in a population that varies with the degree of crowding within the population.

Density Independent
Having influence on individuals in a population that does not vary with the degree of crowding.

Density
Referring to a population, the number of individuals per unit area or volume; referring to a substance, the weight per unit volume.

Deoxyribonucleic Acid (DNA)
A nucleic acid found in most viruses, all bacteria, chloroplasts, mitochondria, and the nuclei of eucaryotic cells, characterized by the presence of a deoyribose sugar in each nucleotide; the genetic material of all organisms except the RNA viruses.

Destruction or Adverse Modification of Critical Habitat
A direct or indirect alteration that appreciably diminishes the value of critical habitat for both the survival and recovery of a listed species.

Deterministic
Referring to the outcome of a process that is not subject to stochastic (random) variation.

Detritivore
An organism that feeds on freshly dead or partially decomposed organic matter.

Detritus
Freshly dead or partially decomposed organic matter.

Developmental Response
Physiological and morphological characteristics an organism develops in response to prolonged exposure to environmental conditions.

Diapause
Temporary interruption in the development of insect eggs or larvae, usually associated iwth a dormant period.

Differentiation
The process of developmental change from an immature to a mature form, especially in a cell.

Diffuse Coevolution
The evolution of traits influencing species interactions, subject to selection from a wide variety of species interacting with different intensities.

Diffuse Competition
The sum of weak competitive interactions with species that are ecologically disstantly allied.

Diffusion
Movement of particles of gas or liquid from regions of high to low concentration by means of their own spontaneous motion.

Digestion
Hydrolysis of complex nutrient compounds into their building-block units.

Dimorphism
Occurrence of two forms of individuals within a population.

Dioecious
Possessing either male or female organs. Describes a group of organisms in which male and femal organs are in different individuals.

Diploblastic
Having body parts derived from two layers during embryologic development.

Distal
An anatomical directional term that means further from the mid-point of the body or further from the point where a limb attaches to the body.

Distinct Population Segment (DPS)
A subdivision of a vertebrate species that is treated as a species for purposes of listing under the Endangered Species Act.

Diving Reflex
A set of complex physiological adaptations some marine mammals have evolved that enables them to dive to great depths for extended periods of time.

Dominant
Occupying a high position in the social hierarchy.

Dormancy
The state of being inactive, quiescent. In plants, particularly seeds and buds, a period in which growth is arrested until environmental conditions become more favorable.

Dummy Nest
Pertaining to the back.

Drag
A force that works in opposition to the direction of movement.

Dummy Nest
A decoy nest that is built in order to attract females, reduce predation, or reduce nest parasitization. If eggs are disturbed in the primary nest, they can be moved to the alternate nest if needed.