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Marine Science Dictionary (DE)

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D

Decapoda: (order) This group includes the crabs, true shrimp, crayfish, and lobsters, among others. Theey include most of the commercially important crustaceans.  They are very diverse and are linked in that all have five pair of walking legs, with the first usually modified into chelae or pinchers.

deep scattering layer: concentration of pelagic animals at the mesopelagic border that migrate upward nightly- so called because it disrupts sonar signals.

demersal: Similar to benthic. Animals associated with the ocean floor or structure. This is more often used to refer to fish.

density: in physics or chemistry the unit mass per unit volume.  In ecology frequently the number of individuals within a given area (population density.)

detritus: broken up parts of dead, decaying  organic material

detritovore: animals that eat detritus,  detritovores allow for the rapid recycling of organic material that would otherwise be lost to an ecosystem

diadromous:  A lifestyle of where fishes live in two areas with different salinities within there life cycle.   See also catadromous and diadromous

diatoms: (fam. Diatomacea) single celled (often colonial)aquatic algae.  Diatoms are characterized by having a two part siliceous cell wall or "frustule." They are an important component of the phytoplankton in many environments, especially higher latitudes.

digestion: The break town of materials for utilization as energy or building blocks.

dinoflagellate: (order Dinoflagellata) single celled aquatic algae with a cellulose cell wall and two locomotor flagella.  The are an important component of the phytoplankton in many areas.  Dinoflagellates may bloom and cause toxic red tides, some are endosymbiotic with animals and many are bioluminescent.

directional selection: type of natural selection, when one extreme of a trait is selected.  Accounts for rapid evolution of a single species.

disphotic zone: The depths of the ocean without plentiful light penetration, and very little photo synthesis. The actual depths of the disphotic zone depend on the turbidity of the water.

disruptive selection: type of natural selection, when two extremes of a trait are selected.  Accounts for rapid speciation.

diurnal: During the day, within the day.  Animals which are active during the daylight.  Contrast with crepuscular and nocturnal.

diurnal tide: the condition where there are two tidal events, one high and one low per tidal day.

divergent evolution:  When traits with a similar form or purpose become dissimilar,  filling different roles.  Animals that are similar become less similar.  An example of this would be the walking limbs of land turtles and the flipper limbs of sea turtles.  At one time these animals had a common ancestor, but evolved to exploit very different resources.  Contrast with convergent evolution.  See also homologous

diversity: see biodiversity

dissolved oxygen (DO): the amount of oxygen dissolved in a sample (of water) usually between 0-10 parts per million (milligrams per liter) or in percent saturation.  Colder water can hold more dissolved oxygen.

-dont:  Refers to teeth or tooth structure,  as in heterodont, meaning "different teeth."

dormancy: a period of inactivity, usually in plants

dorsal: refers to the upper side of bilatteraly symmeterical organisms, especially the fishes

E

ebb tide: the tide condition/ state when the water is falling, when the next tide event is a low tide

ecdysis: The act of shedding and exoskeleton, as arthropods must do periodicaly during growth.

Echinodermata: (phyla) These are marine animals characterized primarily by a spiny endoskeleton and a water vascular system. Echinoderms are, oddly enough an very advanced group of animals. They are scizocoelus meaning that there body cavity is formed by a split in the mesoderm. This is characteristic of the higher animals including the vertebrates. This group exhibits much diversity. There are four major classes separated mainly by body form.  The Asteroidea are the sea stars.  The Ophiuroidea are the brittle stars.  The Echinoidea are the sea urchins and sand dollars.  The Holoththuroidea are the sea cucumbers

ecosystem: The sum of all biotic (living) and abiotic (non living) factors in a given area.

ectotherm:  Any animal that does not contain the heat (energy) produced by its metabolic processes.  This is generally a trait of lower animals.  See also heterotherm, contrast with endotherm.

egestion: The removal of the unusable materials

Ekman spiral, Ekman transport- when the deeper layers of a body of water tend to veer to the right or left (Coriolis effect) and the net movement of a current is at a right angle to the surface movement.

emigration: when animals leave a population. Contrast to immigration.

endemic: When an animal is native to an area it is said to be endemic to that area. This may also be used to refer to a species that is unique to a given area.

endoderm: (endodermis) inner tissue layer, synonymous with gastroderm

endogenous: originating internally, as in an internal mechanism

endoskeleton: Generally the internal cartilaginous and or calcified skeleton of the vertebrates

endotherm: Any animal which contains (turns inward) some of the heat form its metabolic processes.  This is generally a trait of higher animals.  See also homeotherm, contrast with ectotherm

epi- (pelagic/benthic):  Epipelagic and epibenthic refer to the upper reaches of the ocean. The epi zone generally extends from the ocean surface to a depth of 200m. An animal that is benthic and lives in the epi zone would be epibenthic when a pelagic animal in the epi zone would be epipelagic
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epiphyte: A plant or algae which grows on something,  usualy another organism-plant or animal

epidermis: the outer developmental tissue layer, forms nerves, skin and exoskeleton

eutrophic: large amounts of available nutrients, this usually causes an overabundance of simple algaes that choke ecosystems.

eukaryote: organisms that have membrane bound organelles in their cells, includes all plants, animals, fungi and protists

Euphausiacea: (order) Shrimp like crustaceans which occur in large numbers in the higher latitudes. These are the "krill" which are a very important link in the Arctic and Antarctic food webs

eury- (prefix):  This prefix denotes the ability of an organism to live within a wide range of environmental factors, for example a eutyhaline organism can survive within a wide range of salinities. See also steno-.

evolution- (biological): A change in allelic frequencies in successive generations.  Alos used to refer to the theory that all organisms have evolved from common ancestors with modification, leading to the diversity of life on earth

excretion: Ridding the body (on an organismal level) or the cells (on a cellular level) of wastes from biological process

exoskeleton: The hard jointed covering of arthropods, made of chiton.  The exoskeleton does not grow, and as the animal grows it must molt, or undergo ecdysis in order to have an exoskeleton of the correct size

exotic species: a species introduced to an area that (usually) displaces natural species.

endemic: Organisms that are native to an area, animals that evolved within an area or habitat

endo:  Inside of, the inner layer

epiphyta: algae that grow on top of other things, especially other organisms

eury- gr. prefix meaning broad, adapted to withstand a wide range of some parameter.  IE an euryhaline animal can withstand a wide variation in salinity.  Contrast with steno-

Eubacteria: (kingdom)  the "modern" bacteria, characterized by distinct cell walls that contain peptidoglycan

evolution: A change in the allelic frequency of a population over time.  Also refers to the theory that all organisms are descended from previously living organism through descent with modification

evolutionary stable strategy (ESS): A behavioral or morphologic strategy that offers the optimal cost-benefit ratio.  Can not be bettered if widely adapted by most individuals in a population

extant: Any species or group of organisms which have living representatives today

extinct: Any species or group of organisms which do not have living representatives today