abundance: number of individuals in a sample area.

adapted, adaptation: the process of making adjustments to the environment. For example, desert plants have made adjustments so as to be able to live under intense sunlight, on poor quality soils, and with much reduced water supply.

adsorb: adhesion of an extremely thin layer of liquid molecules to the surface of a solid with which they are in contact.

aerial photography: photography of a land surface taken from an aircraft.

algae: simple one-celled or many-celled plants, capable of photosynthesis; usually aquatic.

annuals: plants which complete their full life cycle in one year.

apron: a modified abdomen on the underside of the blue crab which shields the sex organs and, in the female, the fertilized eggs.

aquifer: a permeable body of rock capable of yielding quantities of ground water to wells and springs.

autotomize: to self-amputate an appendage under stress.

biodegradable: a substance that can be broken down by microorganisms into simple, stable compounds such as carbon dioxide and water.

biological clock: any physiological factor that functions in regulating body rhythms.

biomass: the dry weight of living matter, including stored food, present in a species population and expressed in terms of a given area or volume of the habitat.

biota: the animal and plant life of a region or period.

bloom: an overpopulation of algae in a body of water.

bog: wetlands in which water is retained by an accumulation of partially decayed organic matter and which are dominated by sphagnum mosses.

buffer zones: strips of natural plant growth along river and stream banks which help to prevent soil erosion from plowed fields or developed land.

camouflage: an animal's technique of concealing itself by seeming to be part of the natural background.

canopy: layer formed by the leaves and branches of the forest''s tallest trees.

carapace: a shield-like covering (or upper shell) on many crustaceans or turtles.

carnivore: a meat eater.

cast: forms when dirt or mud fill or harden in a mold, creating a raised impression (similar to the jello in a jello mold).

castor glands: a scent gland in the beaver.

climax: the final stage of plant or animal succession; when environmental conditions have been stable long enough for an area to develop a semi-permanent community. For example, rock crumbles, and pioneering plants begin to grow in the sandy soil. As they add mulch and humus, other plants follow - for example, from grasses to shrubs to pine forest to hardwood. Animal types also follow this pattern of succession.

climax forest: a final stage of plant succession, with tree species that change very little over time.

coastal plain: broad low-level plain between a mountain range and a seashore.

community: a group of plant and animal species living together in a habitat.

continental shelf: the relatively shallow flat portion of the sea floor extending from the shoreline to the shelf break, where the sea floor abruptly slopes downward.

crepuscular: animals active in the twilight (dawn or dusk).

crest: the highest point of a wave.

critical habitat: habitat crucial to the survival of the species.

crustacean: an arthropod animal, with jointed feet and mandibles, two pairs of antennae, and a jointed, chitin-encased body.

currents: a part of a body of water moving in one direction; the swiftest part of any stream.

cypress swamp: a wooded wetland dominated by cypress trees.

data base: a complete collection of information on a given topic.

debris: an accumulation of discarded items; trash.

decomposer: those organisms (bacteria, fungi) which convert dead organic materials into inorganic materials; a plant or animal that feeds on dead materials and causes its mechanical or chemical breakdown.

deposition: the laying down of any material.

detritus: fragments of decaying plant, animal, or other organic material.

diatoms: minute planktonic unicellular or colonial algae with skeletons containing silica.

dichotomous key: a guide to identification of plants or animals consisting of a series of pairs of questions or descriptions.

dinoflagellates: minute phytoplankton which move by means of flagellae (long whip like appendages). Some dinoflagellates are responsible for red tides.

diversity: the number of distinct species in a community or ecosystem.

dredging: deepening a waterway using a machine to remove bottom sediment.

ecologist: a scientist who studies the interrelations of living things to one another and their environment.

ecology: the study of the relation of organisms or groups of organisms to each other and to their environment.

ecosystem: all living things and their environment in an area of any size, with all linked together by energy and nutrient flow.

ecotone: a transitional area between two communities.

emigration: the movement of individuals out of a population.

endangered species: a species which is in danger of extinction throughout all or a significant portion of its range.

erosion: the removal or wearing away of soil or rock by water, wind, or other fores or processes.

estuary: a partially enclosed body of water where fresh water and salt water meet.

extinct: no longer existing. An animal or plant facing extinction is one in danger of vanishing from our world.

extirpated: to remove or destroy all of a species from a given part of its range.

eyries: the nests of eagles, usually in the tops of tall (80 ft - 100 ft) trees.

fall line: the boundary between the piedmont and the coastal plain where water falls often occur and where cities (Baltimore, Washington, Fredericksburg, Richmond) are sometimes located.

fetch: the distance which the wind blows over open water.

filter feeder: an animal that filters or screens water flowing through or around its body to capture suspended food.

fledged: young birds which have developed the feathers necessary for flight.

food chain: the transfer of food energy from the source in plants through a series of animals, with repeated eating and being eaten. For example, a green plant, a leaf-eating insect, and an insect-eating bird would form a simple food chain.

food pyramid: a pyramid representing trends in food consumption, with the lowest level (primary producers) having the greatest total biomass, and the higher consumer levels having successively less total biomass.

food web: an interlocking pattern of food chains.

fossil: a remnant or impression of a plant or animal of a past geologic age preserved in the earth's crust.

freshwater marsh: an area which is dominated by herbaceous plants with roots in soil covered part or all the time by fresh water and leaves held above water.

girdle: to remove the bark of a tree in a ring around the trunk.

groundwater: water within the earth which supplies wells and springs.

habitat: the place where a plant or animal lives.

herbaceous: a plant which does not develop woody material and dies back at the end of a growing season.

hydroids: the sessile, polypoid stage of Hydrozoans.

immigration: movement into a population.

indicator species: an organism so closely associated with an ecosystem that its presence or absence is indicative of the health of the ecosystem.

inorganic: mater not originating from living things.

intertidall: the shore zone located between the low-water mark and the high-water mark.

invertebrate: an animal lacking a backbone and internal skeleton.

larvae: a young form of an animal which is unlike the adult and must metamorphosize before taking on adult characteristics.

limnology: the area of science dealing with the study of freshwater aquatic ecology.

literature search: a thorough exploration of all information published about a given topic.

MARPOL: an international treaty prohibiting the dumping of plastic in the oceans.

macroinvertebrate: a large invertebrate such as a crab, clam, or oyster.

maritime forest: a forest community within range of salt spray.

megalops: the last larval stage of a crab before metamorphosis into a juvenile.

mold: an impression of an organism left in mud or other material (similar to a jello mold).

molt: to shed the old carapace before forming a new one.

moving tide: a flooding or ebbing tide.

nictitating membrane: in many vertebrates, a membrane of the eye capable of extending over the eyeball.

nocturnal: animals active at night.

nondegradable: incapable of being broken down into simple compounds.

nonpoint source: a source of water pollution which is not readily identifiable; for example, runoff from farms or dumping from boats.

nutrients: compounds or elements required by organisms for growth and reproduction.

nymph: an immature larval stage of some insects.

omnivore: an animal which eats both plant and animal materials.

organic: matter originating from living things.

orientation: determination of direction (east, south, west, north).

outbuildings: buildings separate from but accessory to a main house; for example, a stable, smokehouse, or kitchen.

pellet: a mass of undigested material regurgitated by a carnivorous bird.

percolate: the flow of ground water due to gravity through the pores in rock or soil.

perennial: a plant that lives for several years, typically supported by underground rhizomes, tubers, or bulbs.

permineralization: a fossilization process whereby minerals are deposited in the pore spaces of originally hard animal parts.

persistent pesticide: a pesticide which does not break down but remains in the environment in a toxic state.

petrifaction: a fossilization process whereby inorganic matter dissolved in water completely replaces original organic mater, converting it to a stony substance.

photodegradable: capable of decomposing when exposed to light.

phytoplankton: plants (usually microscopic) that float at or near the surface of open water.

piedmont: lying or formed at the base of a mountain range.

point source: a source of pollution which is easily identified; for example, a factory or a sewage treatment plant.

predator: an animal that kills and eats other animals.

prey: animals that are killed and eaten by other animals.

primary consumers: herbivores which eat primary producers.

primary dune: the dune closest to the ocean.

primary producers: green plants which are able to manufacture food from simple inorganic substances.

primary succession: the ecological succession of vegetation that occurs in passing from barren earth or water to a climax community.

quadrat: a sampling plot used for ecological or population studies.

qualitative: relating to quality or kind.

quantitative: relating to number or amount.

raptor: bird of prey; for example, eagle, hawk, and owl.

regression: retreat of the sea from land areas.

runoff: water that drains or flows off the surface of the land.

salt-water intrusion: displacement of fresh surface water or groundwater by salt water due to its greater density.

salt water marsh: an area dominated by vegetation which is periodically flooded with salt water, due to tidal action.

salt wedge: a wedge-shaped intrusion of salty ocean water into an estuary or tidal river; it slopes downward in the upstream direction, and salinity increases with depth.

satellite photography: photography taken from a satellite.

scat: an animal fecal dropping.

sebaceous gland: a glad associated with a hair follicle which produces sebum (a mixture of fat, cellular debris, and keratin).

secondary consumers: carnivores which prey upon primary consumers.

secondary dune: a dune on the landward side of the primary dune.

secondary succession: succession that begins with a state in which other organisms were already present; for example, abandoned cropland.

sharecroppers: tenant farmers who work the land of another in exchange for an agreed share of the value of the crop.

slack tide: the period of reversal between ebb and flood currents; the speed of the current is very weak or zero.

sponge: any of a phylum (Porifera) of aquatic lower invertebrate animals that are essentially double-walled cell colonies and are permanently attached as adults.

subcutaneous: under the skin.

submerged aquatic vegetation (SAV): underwater aquatic rooted plants.

succession: the orderly, gradual, and continuous change in species composition and community structure over time.

succulent: having fleshy tissues designed to conserve moisture.

swamp: a wetland dominated by trees such as cypress or tupelo.

talons: sharply hooked claws on the foot of a bird of prey.

territoriality: the instinctive compulsion to gain and defend a fixed and exclusive area maintained by an individual or group.

tertiary consumers: carnivores which prey upon secondary consumers.

threatened species: a species which is likely to become endangered.

tides: the periodic rising and falling of the oceans resulting from lunar and solar forces acting upon the rotating earth.

toxins: poisons.

transect: a cross section of an area used as a sample for recording, mapping, or studying vegetation.

transgression: extension of the sea over land areas.

triangulation: a method for finding a position by means of bearings from two fixed point a known distance apart.

tributary: a stream feeding a larger stream or river.

trough: the lowest point of a wave.

turbidity: cloudiness in water derived from algae, suspended silt, or other impurities.

water cycle: the cycle of water from groundwater, to stream, to river, to ocean, to clouds (by evaporation), to rain, and back to groundwater.

watershed: the drainage area of a stream, river, or estuary.

wave frequency: the number of waves to pass a point in a unit of time.

wave height: the vertical distance between the wave trough and the preceding crest.

wetlands: any land area that tends to be regularly wet or flooded.

wetland buffer: a wetland which acts to reduce wave force and lessen shoreline erosion.

woody plants: plants which contain wood fibers and have persistent living parts above ground year round.

zoea: an early larval stage of crabs and shrimp.

zooplankton: aquatic animals that drift passively with the currents.