Daily sluggishness that some animals experience. A period of
inactivity that is normally induced by cold; observed in numerous
ectotherms and also endotherms; often used to describe the specific
physiological state of endotherms with a circadian cycle of lowered
body temperature and depressed metabolic rate.
dalton Atomic Weight Unit ;
the mass of one proton or one neutron.
that part of the photosynthetic process that, in the absence
of light, utilizes the preformed high-energy molecules ATP
and NADPH2 to synthesize complex organic molecules; the Calvin
Darwinism Theory of evolution emphasizing common descent of all living
organisms, gradual change, multiplication of species and natural
in a scientific experiment, or descriptive observations, upon
which a conclusion is based.
Nematode juvenile in which development is arrested during unsuitable
conditions and resumed when conditions improve.
In digenetic trematodes the embryonic cells that develop from
sporocysts and give rise to rediae.
The number of hours that sunlight illuminates a given area on
earth; dependent on the angle of the earth relative to the rays
of the sun.
A plant whose flowering is not controlled by the length of day.
A reaction in which an amino group, _NH2, is enzymatically removed
from a compound.
debt-for-nature swap Forgiveness
of international debt in exchange for nature protection in developing
countries. Environmental groups and nongovernmental organizations
often pay banks to write off uncollectable debts of developing
countries at a steep discount in exchange for a promise by the
debtor country to establish nature preserves.
Ten-hooked larva that hatches from the egg of a cestodarian
tapeworm. Also called a lycophora.
Crustaceans with five pairs of walking legs and a well-developed
carapace. The group includes the shrimps, lobsters, hermit crabs,
The removal of a single carbon atom as CO2
from an organic molecule.
Referring to plants that lose all their leaves during the cool
season; as opposed to evergreen plants.
Forest biome in which the dominant trees are deciduous.
A catastrophic deterioration of a species, community, or whole
ecosystem; accelerates as functions are disrupted or lost in a
heterotrophic bacteria and fungi that obtain organic nutrients
by breaking down the remains or products of other organic compounds;
their activities help cycle the simple compounds back to the autotrophs.
An agent that relieves nasal or respiratory congestion.
Reasoning from the
general to the particular, that is, from given premises to their
deep (bottom) layer
The deepest and coldest of the three layers of the ocean.
A philosophy that calls for a profound shift in our attitudes
and behavior based on voluntary simplicity; rejection of anthropocentric
attitudes; intimate contact with nature; decentralization of power;
support for cultural and biological diversity; a belief in the
sacredness of nature; and direct personal action to protect nature,
improve the environment, and bring about fundamental societal
deep scattering layer (DSL)
A sound-reflecting layer of many types of organisms that
migrates daily from the mesopelagic zone to the epipelagic zone.
The dark waters below the mesopelagic zone.
A fan-like accumulation of sediment at the base of a submarine
deep-sea hot spring
See hydrothermal vent.
de = away from; ferens = carry.
The concept of low levels of irrigation to achieve a moderate
level of productivity; even though yields are not maximized, limited
water supplies are conserved.
Host in which a parasite achieves sexual maturity. If there is
no sexual reproduction in the life of the parasite, the host most
important to humans is the definitive host.
The genetic code is said to be degenerate because more than one
three-base sequence in DNA can code for one amino acid.
The death or functional impairment of cells connected to destroyed
or severely damaged neurons.
Deterioration in water quality due to contamination
or pollution; makes water unsuitable for other desirable purposes.
degree of genetic determination
See heritability in the broad sense.
Mature fruit that splits open to release the seed.
Fruit that splits open at maturity, facilitating seed dispersal.
Sensory papilla on each side near the anterior end of some nematodes.
A controversial amendment to the Federal Food, Drug, and Cosmetic
Act, added in 1958, prohibiting the addition of any known cancer-causing
agent to processed foods, drugs, or cosmetics.
Occurs when fertilization of an egg does not occur immediately
following coitus, but may be delayed for weeks or months.
delayed implantation A
pattern in the reproductive cycle of some mammals causing the
blastocyst to remain dormant in the female's uterus for some time
before implantation on the uterine wall.
delayed response problem
An operant conditioning procedure in which the test animal sees
the experimenter set up the test situation, including what will
be the correct response, and then must wait until the experimenter
provides the animal with an opportunity to respond.
delayed type hypersensitivity (DTH)
Manifestation of cell-mediated immunity, distinguished from
immediate hypersensitivity in that maximal response is reached
about 24 hours or more after intradermal injection of the antigen.
The lesion site is infiltrated primarily by monocytes and macrophages.
A mutation resulting from the loss of a small segment of DNA.
A mutation in which a base pair is deleted
Fan-shaped sediment deposit found at the mouth of a river.
delta [shaped like the Greek letter], triangular.
The amount of a product that consumers are willing and able to
buy at various possible prices, assuming they are free to express
A small, local subpopulation. Isolated subpopulations sometimes
display genetic changes that may contribute to evolutionary change
in the subpopulation.
A bottom-dwelling fish.
demographic transition A
pattern of falling death and birth rates in response to improved
living conditions; could be reversed in deteriorating conditions.
Vital statistics about people: births,
marriages, deaths, etc.; the statistical study of human populations
relating to growth rate, age structure, geographic distribution,
etc., and their effects on social, economic, and environmental
The class of poriferans whose members have monaxon or tetraaxon
siliceous spicules or spongin. Leuconoid body forms are present
and vary in size from a few centimeters to 1 m in height.
Disruption of bonds holding a protein in its three-dimensional
form, such that its polypeptide chain(s) unfolds partially or
completely. Denaturation can be caused by changes in pH, salt
concentration, or environmental temperature.
To change the configuration of a protein molecule such that it
loses specificity and no longer functions as an enzyme.
Any of nerve cell processes that conduct
impulses toward the cell body.
science of studying growth rings of trees to determine past conditions.
Study of the annual rings of trees in order to interpret climatic
changes in the past.
Virus disease transmitted by mosquitoes.
Free-living soil bacteria that convert nitrates to gaseous
nitrogen and nitrous oxide.
The weight (or more correctly the mass) of a given volume of a
A notation that indicates the number of incisors, canines, premolars,
and molars in the upper and lower jaw of a mammal.
A small toothlike process.
(denticulate) Small, toothlike projections.
deoxyribonucleic acid A polymer of deoxyribonucleotides that is in the form of a double helix; DNA is the genetic molecule of life in that it codes for the sequence of amino acids in proteins; contains nucleotide monomers with deoxyribose sugar and nitrogenous bases adenine (A), cytosine (C), guanine (G), and thymine (T).
sugar having 1 oxygen atom less than ribose; a component of deoxyribonucleic
dependency ratio The
number of nonworking members compared to working members for a
What may change (e.g., aggression) in response to manipulation
of an independent variable (e.g., food supply) by the experimenter.
Water flowing into a plasmolized cell to correct the process
that would cause cellular death from dehydration.
The loss of an electrical charge on the surface of a membrane.
The reduction in the difference in charge (potential) between
the outside and inside of a membrane.
An animal that feeds on organic matter that settles on the bottom.
Compare suspension feeder.
deposit feeding The
type of feeding whereby an animal obtains its nutrients from the
sediments of soft-bottom habitats (mud or sands) or terrestrial
depressant Psychoactive drug that has a sedative effect on the central nervous system; actions include dulling mental awareness and inducing sleep.
Experimental manipulations involving removal of particular types
of stimuli (e.g., social, sensory, motor) to ascertain the effects
later in development.
dermal branchiae Thin folds of the body wall of a sea star that extend between ossicles and function in gas exchange and other exchange processes.
Pertaining to the skin; cutaneous.
Tissue that covers surfaces in plants.
Infection or inflammation of the skin.
Certain imperfect fungi that cause skin diseases in humans; includes
the organisms causing ringworm and athlete's foot.
layer of the skin deep to the epidermis, consisting of a dense
bed of vascular connective tissue.
desalination)Removal of salt from water by distillation, freezing,
A type of biome characterized by low moisture levels (below 25
cm per year), and infrequent and unpredictable precipitation.
Daily and seasonal temperatures fluctuate widely. Deserts are
characterized by cacti and desert shrubs or sagebrush. Animals
include birds, rodents, reptiles, and numerous species of arthropods.
A process by which fragile, semiarid ecosystems lose productivity
because of loss of plant cover, soil erosion, salinization, or
waterlogging. Usually associated with human misuse.
Dehydration. The process of drying.
Buttonlike plaque serving as
an intercellular connection.
A dominant individual that controls resources.
determinate cleavage The type of cleavage, usually spiral, in which the fate of the
blastomeres is determined very early in development; mosaic cleavage.
Pertaining to a leaf or stem that stops growing after differentiating
into a terminal reproductive unit.
Organisms that consume organic litter, debris, and dung.
Dead organic matter and
the decomposers that live on it.
A miscellaneous assemblage of fungi also termed the imperfect
fungi because the sexual reproductive features are either not
known, not used, or have been reduced
Animals in which the anus forms from, or in the region of, the
blastopore; often characterized by enterocoelous coelom formation,
radial cleavage, and the presence of a dipleurulalike larval stage.
A group of
higher phyla in which cleavage is indeterminate (regulative) and
primitively radial. The endomesoderm is enterocoelous, and the
mouth is derived away from the blastopore. Includes Echinodermata,
Chordata, and a number of minor phyla. Compare with Protostomia.
Type of parthenogenesis in which all individuals are uniparental
but in which both males and females occur.
Posterior half of a cephaline gregarine protozoan.
In the life cycle of some mesostigmatid mites, a nonfeeding stage
that molts into the adult.
Incompletely developed larva that hatches from the egg of a chigger
The summation of all activities leading to changes in cells,
tissues, organs, or organisms; a genetically controlled sequence.
The study of how organisms, their
A geological period of the Paleozoic era beginning about 400
million years ago. During this period major diversification of
the early land plants occurred.
The temperature at which condensation occurs for a given concentration
of water vapor in the air.
dextral Pertaining to the right; in gastropods,
shell is dextral if opening is to right of columella when held
with spire up and facing observer.
characterized by a high blood glucose level and the appearance
of glucose in the urine due to a deficiency of insulin or the
inability of body cells to respond to insulin; diabetes mellitus.
A period of arrested development in the
life cycle of insects and certain other animals in which physiological
activity is very low and the animal is highly resistant to unfavorable
A period of dormancy, common in insect species, which occurs during
the more rigorous portions of the annual climatic cycle.
The domed respiratory muscle between thoracic and abdominal compartments
Ciliated somatodermal cells located between the parapolar and
uropolar cells of a mesozoan.
Amniotes in which the skull bears
two pairs of temporal openings; includes reptiles (except turtles)
A space, gap.
Phase of the cardiac cycle during which
a heart chamber wall is relaxed; also diastolic pressure.
The blood pressure measurement during the interval between heartbeats;
it is the second number shown in a blood pressure reading.
A powdery, soil-like material formed by the glass cell walls
of dead diatoms deposited on the marine floor.
A biogenous sediment that consists mostly of the siliceous frustules
of diatoms. It is known as diatomaceous earth when found inland.
Unicellular and eukaryotic autotrophs with a siliceous frustule;
Pertaining to the division or forking of a single axis into two
A class of angiosperms in which the seedlings typically possess
two cotyledons; commonly abbreviated to dicot.
A sudden population decline; also called a population crash.
Condition in which ecdysis processes are going on continuously
and one ecdysis cycle grades rapidly into another.
differentially permeable membrane
A membrane that permits the passage of certain types of particles
and inhibits the passage of others; also termed selectively permeable
chemical and physical changes associated with the developmental
process of an organism or cell.
Secondary xylem characterized by the same-sized vessels
and tracheids throughout the growing season so that growth rings
are difficult or impossible to detect.
The random movement of molecules from one location to another
because of random thermal molecular motion; net diffusion always
occurs from a region of higher concentration to a region of lower
di = two; gaster = stomach or belly.
The process by which larger molecules of food substances are
broken down into smaller molecules that can be taken up by the
digestive system; hydrolysis.
An enzyme-producing gland in several groups of invertebrates
where digestion and absorption take place.
the digits with the posterior part of the foot raised; compare
A hybrid whose
parents differ in two distinct characters; an offspring having
two different alleles at two different loci, for example, A/a
A genetic cross between parents that differ for two traits.
Mycelium of some fungi that have two separate haploid nuclei in
A condition in which unrestrained population growth causes the
standard of living to decrease to a subsistence level where poverty,
misery, vice, and starvation makes life permanently drab and miserable.
This dreary prophecy has led economics to be called "the
Having more than one form, size, or appearance; usually referring
to the difference between males and females of a species.
Existence within a species of two
distinct forms according to color, sex, size, organ structure,
and so on. Occurrence of two kinds of zooids in a colonial organism.
Unicellular, eukaryotic, mostly autotrophic organisms with two
Characterized by having separate sexes; that is, an individual
is either male or female, but never both. "Gonochoristic"
means the same thing.
A tail that tapers
to a point, as in lungfishes; vertebral column extends to tip
and permanent sets of teeth successively.
diploblastic Animals whose body parts are organized into layers that are derived embryologically from two tissue layers: ectoderm and endoderm. Animals in the phyla Cnidaria and Ctenophora are diploblastic.
Having the somatic (double,
or 2N) number of chromosomes or twice the number characteristic
of a gamete of a given species.
diploid (2n) cell
A cell, such as a body cell, that contains two similar sets of
chromosomes, one from each parent. Compare haploid.
The class of arthropods whose members are characterized by having
two pairs of legs per apparent segment and a body that is round
in cross section. Millipedes.
Strigeoid metacercaria in the family Diplostomatidae.
Larval stage in the life cycle of the monogenean Diplozoon.
Civil disobedience, guerrilla street theater, picketing, protest
marches, road blockades, demonstrations, and other techniques
borrowed from the civil rights movement and applied to environmental
In arthropods refers to development in which a juvenile hatches
from the egg, and the juvenile is not distinctly different from
adult except in size and maturity.
A measure of an individual's potential to contribute genes to
future generations via personal reproduction.
Insect flight that is accomplished by flight muscles acting on
wing bases and in which a single nerve impulse results in a single
wing cycle; also called synchronous flight. See indirect (asynchronous)
directional selection Natural
selection that occurs when individuals at one phenotypic extreme
have an advantage over individuals with more common phenotypes.
Sugar consisting of two
monosaccharides; example: sucrose is composed of glucose and fructose.
The amount of water that passes a fixed point in a given amount
of time; usually expressed as liters or cubic feet of water per
See equilibrium community.
An animal that does not feed all the time; instead it generally
eats large meals sporadically and does not spend time in the continuous
pursuit of prey.
The amount we discount or reduce the value of a future payment.
When you borrow money from the bank at 10 percent annual interest,
you are in effect saying that having the money now is worth 10
percent more to you than having the same amount one year from
A form of communication that is digital, or all or none; usually
given at the same intensity each time, such as an alarm call.
A variable that can take on only certain values (usually integers),
as opposed to a continuous variable.
The ability to detect differences between two or more stimuli
and make choices based on those differences in a learning situation.
A deleterious change in the body's condition in response to destabilizing
factors, such as nutrition, chemicals, or biological agents.
A more or less permanent movement of an individual from an area,
such as movement of a juvenile away from its place of birth.
An innate or stereotypic response to a stimulus that seems inappropriate
or irrelevant to the situation.
Any behavior pattern especially adapted in physical form or frequency
to function as a social signal in communication.
A color pattern that helps break the outline of an organism.
Natural selection that occurs when individuals of the most common
phenotypes are at a disadvantage; produces contrasting subpopulations.
The breaking up of a molecule into ions when placed in water or
dissolved organic matter (DOM)
Organic matter that is dissolved in water rather than being in
dissolved oxygen (DO)
contentAmount of oxygen dissolved in a given volume of water
at a given temperature and atmospheric pressure; usually expressed
in parts per million (ppm).
distal Away from the point of attachment of a structure on the body (e.g., the toes are distal to the knee).
distal cytoplasm Distal
cytoplasmic layer in the tegument of Monogenea, Digenea, and Cestoidea.
Boiling of a liquid to evaporation and subsequent condensation
of the vapors for the purposes of purification and concentration.
Alcoholic beverage with an alcoholic content between 80-100 proof,
obtained by distillation of a beer or wine.
Fluke with two suckers, oral and ventral.
A linkage between the sulfur atoms of two different amino acids
in a protein.
Pertaining to daily cycles or events.An animal with an activity
period during the light portion of the daily cycle.
A tidal pattern with a high and a low tide each day.
the suite of internal responses, including bradycardia and peripheral
circulation shutdown, that occurs during dives by an air-breathing
(species diversity, biological diversity)The number of species
present in a community (species richness), as well as the relative
abundance of each species.
The reflex certain animals have to stay underwater for prolonged
periods of time.
Taxonomic rank that includes related classes; synonymous to phylum
used in animal systematics.
Twins that arise from two different zygotes, hence, individuals
no more closely related than two different-aged siblings.
Deoxyribonucleic acid; the long, double-helix molecule in
the nucleus of cells that contains the genetic code and directs
the development and functioning of all cells.
doctrine of signatures
Early concept that the Creator placed certain items on earth for
humans and identified their intended use by their shape.
domestic sewage Wastewater
from homes and non-industrial buildings. Compare industrial
A plant that has been genetically changed from the wild type
due to artificial selection.
A social ranking, formed through agonistic behavior, in which
individuals are associated with each other so that some have greater
access to resources than do others.
A gene that masks one or more of its alleles. See recessive.
Those plant species in a community that provide a food base for
most of the community; they usually take up the most space and
have the largest biomass.
A species that exerts an overriding influence in determining the
characteristics of a community.
(1) The most prevalent species in a plant community. (2) The
allele that has its trait expressed. (3) A gene that has its phenotypic
expression appear in the offspring, regardless of the nature of
its allelic partner.
A trait whose phenotype is determined by a single allele at a
Having reduced metabolic and respiratory activity.
The back of an animal; usually the upper surface; synonymous with
posterior for animals that walk upright.
Dorsal plate on the body of a mesostigmatid mite.
A covalent bond sharing two pairs of electrons.
The fusion of egg and sperm resulting in a zygote, and the simultaneous
fusion of sperm with two polar nuclei resulting in the formation
of endosperm that characterizes all angiosperms.
A helix composed of two molecules winding around each other, as
Disease of horses and other equids caused by Trypanosoma equiperdum.
down feathers Feathers
that provide insulation for adult and immature birds.
A congenital syndrome including mental retardation, caused by
the cells in a person's body having an extra chromosome 21; also
called trisomy 21.
Resistance to movement through water or any other medium.
A very long fishing net that is allowed to drift for a long time
before it is pulled on board.
Uses pipe or tubing perforated with very small holes to deliver
water one drop at a time directly to the soil around each plant.
This conserves water and reduces soil waterlogging and salinization.
Manifestations of specific motivations corresponding to specific
An old term for congestive heart failure which produces edema
and resulting decrease in manual dexterity, causing one to drop
An environmental condition in which precipitation is not sufficient
to maximize biological productivity.
drowned river valley
(or coastal plain) estuaryAn estuary that is formed when sea
level rose at the end of the last glacial age.
A fleshy fruit with a one-carpeled ovary and only one seed.
The endocarp is hard and stony, tightly enclosing the seed; the
mesocarp is fleshy, and the exocarp is soft and thin; example:
dry alkali injection
Spraying dry sodium bicarbonate into flue gas to absorb and neutralize
acidic sulfur compounds.
Fruit in which the cells of the pericarp are dry (dead) at maturity.
dual-gland adhesive organ
Organs in the epidermis of most turbellarians, with three cell
types; viscid and releasing gland cells and anchor cells.
ductus = leading.
Platyhelminth tegument gland with two types of cells, one producing
an adhesive substance and the other a releasing substance.
The first and shortest portion of the small intestine lying between
the pyloric end of the stomach and the jejunum.
duplications The presence of two copies of one or more loci in a chromosome.
The outermost meninx.
One of the groups of two chromosomes formed
by the division of a tetrad during the first meiotic division.
Difficult or labored breathing.