8H Science Units and Worksheets
A
Abdomen -- the portion of a tetrapod's body between the thorax and pelvic girdle that contains the visceral organs.
Abductor -- a muscle that performs the action.
Abiotic -- a non-living component of the environment.
Aboral -- the part of the body farthest from the mouth.
Abscess -- dead cells and tissue fluid confined in a localized area, causing swelling.
Absorptive feeding -- a means of taking up dissolved food material through specialized organs or across the body wall.
Acclimation -- the change in tolerance of an animal for a condition in its environment.
Accretion -- an object grown by the process of externally layering material one layer on top of another (pearls).
Acronomic -- describes an animal that dwells in high places (treetops, cliffs, etc.).
Adam's Apple -- the popular name for the thyroid cartilage that is seen in the front of a man's throat.
Adaptation -- an anatomical structure, physiological process, or behavioral trait that evolved by natural selection and improves an organism's ability to survive and leave descendants.
Adenoids -- the pathological enlargement of the lymphoid
Adrenal Glands -- a pair of glands on the kidneys which secrete adrenalin and other hormones.
Adrenaline -- a hormone produced by the adrenal gland.
Aerate -- to supply with oxygen.
Aerial -- pertaining to being in the air, such as a root projecting from an aboveground stem.
Aerobic -- an oxygen-dependent form of respiration.
Afterbirth -- the placental and fetal membranes expelled from the uterus after childbirth.
Aggressive mimicry -- a technique for capturing prey in which the predator uses lures or other means to misinform the prey.
Agnatha -- a superclass of vertebrates whose members lack jaws and paired appendages and possess a cartilaginous skeleton and a persistent notochord. Lampreys and hagfishes.
Alate -- describes an organism with wings.
Alga -- a photosynthetic protist containing plastids. Any of several groups of autotrophs that lack the structural features (true leaves, roots, and stems) of the higher plants.
Alien species (exotic species) -- a species introduced by humans.
Alimentary -- having to do with nutrition or nourishment.
Alimentary canal -- the channel in an animal through which food passes.
Alkaloid -- a group of nitrogen-containing compounds having diverse structures; many alkaloids have medicinal, hallucinogenic, or toxic properties.
Allele -- alternative forms of genes coding for the same trait.
Allergens -- substances that activate the immune system and cause an allergic response; may not be directly antigenic themselves but may make other materials antigenic.
Allopatric -- found in separate and mutually exclusive geographical regions.
Allopatric speciation -- the formation of new species by a process involving geographic barriers.
Alpine -- the high, treeless biome of mountains that consists of grasses algae and/or lichens.
Alternate -- leaf arrangement in which there is only one leaf.
Altricial -- an animal that is helpless at hatching or birth.
Altruism -- the principle or practice of unselfish concern for, or devotion to, the welfare of others.
Alveolus -- a lung air sac where gas exchange with the blood occurs.
Amino acid -- an organic molecule including one or more amino (NH 2 ) and acid (COOH) groups; one of the 20 nitrogen-containing molecules that make up proteins.
Amitosis -- the anatomical term given to cell reproduction by direct division.
Amniocentesis -- a procedure for withdrawing a sample of fluid around the developing embryo for examination of chromosomes in the embryonic cells and other tests.
Amnion -- a membranous sac which surrounds the embryo; it is developed in reptiles, birds and mammals, but not in amphibians or fishes.
Amniotic egg -- the egg of reptiles, birds, and mammals.
Amphibia -- the class of vertebrates whose members are characterized by skin with mucoid secretions, which serves as a respiratory organ. Developmental stages are aquatic and are usually followed by metamorphosis to an amphibious adult. Frogs, toads, and salamanders.
Amplexus -- the positioning of a male amphibian dorsal to female amphibian, his forelimbs around her waist. During amplexus, the male releases sperm as the female releases eggs.
Ampulla (Pl. Ampullae) of Lorenzini -- one of several sensory structures in the head of sharks that detect weak electric fields.
Anabolic -- chemical reactions that synthesize and require energy.
Anadromous -- refers to fishes that migrate up streams from the sea to spawn.
Anaerobic -- not dependent on oxygen for respiration.
Anal fin -- each of the last pair of ventral fins of fishes.
Analgesic -- a pain-relieving remedy.
Anatomy -- the structure and organization of living creatures.
Androgen -- any substance that contributes to masculinization, such as the hormone testosterone.
Androsterone -- an animal hormone not synthesized by plants.
Anemia -- low levels of hemoglobin due to iron deficiency or lack of red blood cells.
Angiosperm -- the group of plants characterized by having flowers as their sexual reproductive structures.
Animalia -- the kingdom of organisms whose members are multicellular, eukaryotic, and heterotrophic. Fish, amphibians, reptiles and mammals are examples.
Ankle -- the joint connecting the foot with the leg.
Annelida -- the phylum of animals whose members are segmented and wormlike. Annelids have a complete digestive tract and a ventral nerve cord.
Annual -- a plant that lives for a single growing season.
Annual ring -- the ring of a tree that corresponds in temperate regions to a chronological year.
Ante -- a prefix meaning before.
Antenna -- a sensory appendage on the head of arthropods, or the second pair of the two such pairs of structures in crustaceans.
Anterior -- the head end of an organism, or (as an adjective) toward that end.
Anther -- the male reproductive organ enclosing and containing the pollen grains.
Anthozoa -- the class of cnidarians whose members are solitary or colonial polyps. Sea anemones and corals.
Antibiotic -- a substance that inhibits the growth of microorganisms.
Antibody -- immunoglobulin protein, produced by B cells (or plasma cells derived from B cells), that binds with a specific antigen.
Anticoagulant -- a substance that prevents blood clotting.
Antigen -- a foreign substance to which lymphocytes respond; also known as an immunogen because it induces the immune response.
Aorta -- the largest artery in the human body. It carries blood from the heart to the arms, legs and head.
Apex predator -- the consumer at the end of a food chain or web; a carnivore that ordinarily has no predator under normal conditions.
Aquaculture -- the farming of marine and freshwater organisms.
Arachnida -- the class of arthropods whose members are mostly terrestrial, possess book lungs, or tracheae, and usually have four pairs of walking legs as adults. Spiders, scorpions, ticks, mites, and harvestmen.
Arbor -- a Latin word meaning tree.
Arboreal -- a term describing an organism living in trees.
Archaea -- the early prokaryotes, differing from bacteria in having unusual types of metabolism, membrane lipids, and amino acid and DNA and RNA base sequences. Today these organisms inhabit extreme environments.
Archosauria ("ruling lizards") -- the Crocodylia, Pterosauria, Dinosauria, and several other closely related groups of animals.
Artery -- the vessel that carries blood away from the heart.
Arthropoda -- the phylum of animals whose members possess a jointed exoskeleton and a ventral nervous system. Insects, crustaceans, spiders, and related animals.
Artiodactyl -- one of an order of mammals with two or four digits on each foot.
Asexual -- lacking sexual reproduction.
Asthma -- a distressing disease characterized by shortness of breath, wheezing, and bronchial muscle spasms.
Asymmetry -- without a balanced arrangement of similar parts on either side of a point or axis.
Atherosclerosis -- a disease characterized by fatty plaques forming in the inner lining of arteries.
Athlete's Foot -- a disease caused by fungi that flourish under warm, wet conditions.
Atrium -- one of the chambers of the heart; also, the tympanic cavity of the ear.
Auricle -- (1) reservoirs within the heart which receive blood from the veins, (2) the portion of the external ear not connected within the head.
Autoimmunity -- an immune response to ones' own proteins or other antigens.
Autonomy -- the self amputation of an appendage. For example, the casting off of a section of a lizard's tail caught in the grasp of a predator. The autotomized appendage is usually regenerated.
Autotroph -- an organism that makes its organic nutrients from inorganic raw materials by using an external energy source, such as light energy. Plants.
Autotrophic -- having the ability to synthesize food from inorganic compounds.
Aves -- a class of vertebrates whose members are characterized by scales modified into feathers for flight, endothermy, and amniotic eggs. The birds.
Axial skeleton -- the portion of the skeleton that supports and protects the organs of the head, neck, and trunk.
Axis -- the 2nd cervical vertebrae. It provides the pivot for the atlas and the head.
B
Bacillus -- a rod-shaped bacterium.
Bacteria -- the prokaryotic and unicellular microorganisms included in the kingdom Monera.
Baleen -- the filtering plates that hang from the upper jaws of baleen whales.
Baleen whales -- the filter-feeding whales.
Bark -- those portions of a woody plant stem or trunk exterior to the vascular cambium.
Barnacles -- crustaceans that live attached to surfaces and are typically enclosed by heavy calcareous plates.
Batesian mimicry -- evolution by one species to resemble the coloration, body shape, or behavior of a related species that is protected from predators by a venomous stinger, bad taste, or some other adaptation.
Benthic -- pertaining to the bottom region of an ocean, lake, or pond.
Berry -- a fleshy, two- or multiple-carpeled ovary, each carpel having many seeds.
Beta-carotene -- the yellow to red pigment in plants that converts to vitamin A in animals.
Biceps -- a long fusiform muscle on the front of the arm used to flex the elbows.
Bicuspid -- either of the two double-pointed teeth that in humans are situated between the canines and the molars on each side of each jaw.
Biennial -- a plant that completes its life cycle within two growing seasons. A carrot.
Bilateral symmetry -- an animal body plan with mirror image left and right sides.
Bile -- a fat emulsifying fluid secreted by the liver, stored in the gall bladder and poured into the small intestine via the bile duct.
Bimodal breathing -- the ability of an organism to exchange respiratory gases simultaneously with both air and water; usually using gills for water breathing and lungs for air breathing.
Binary fission -- asexual reproduction in protists in which mitosis is followed by cytoplasmic division, producing two new organisms.
Binomial -- the two names, genus and species, comprising the scientific name.
Binomial nomenclature -- a system of naming species using two names, the first of which refers to the genus.
Biocentrism -- the belief that all creatures have rights and values; being centered on nature rather than humans.
Biochemistry -- the chemistry of living organisms and of vital processes.
Biocide -- a broad-spectrum poison that kills a wide range of organisms.
Biodegradable -- a chemical that can be broken down by bacteria or other organisms.
Biodiversity -- the genetic, species, and ecological diversity of the organisms in a given area.
Biogeography -- the study of the distribution of life on earth.
Biological clock -- an internal timing mechanism that involves both an internal self-sustaining pacemaker and cyclic environmental synchronizers.
Biology -- the study of all living organisms.
Bioluminescence -- a method of light production by living organisms in which usually certain proteins, oxygen and enzymes are present.
Biomass -- the weight of total living organisms or of a species population per unit of area.
Biomes -- distinctive associations of plant and animal populations; characterized by certain geographical boundaries and specific climatic and geographical features.
Biosphere -- Earth and all of its ecological interactions considered as a single system.
Biotechnology -- the use of living organisms to provide products for humanity; using genetic engineering to create organisms with useful traits.
Biotic factor -- the living components in the environment.
Bipeds -- animals that walk upright on two legs.
Birds (class aves) -- vertebrates that have feathers and lay eggs with calcified shells on land.
Bivalves (class bivalvia) -- the clams, mussels, and other molluscs that possess a two-valved shell, filtering gills, and a shovel-like foot.
Bivalvia -- the class of molluscs whose members are enclosed in a shell consisting of two dorsally hinged valves, lack a radula, and possess a wedge-shaped foot. Clams, mussels, oysters.
Black lung disease -- inflammation and fibrosis caused by accumulation of coal dust in the lungs or airways.
Black smoker -- a chimney-like accumulation of mineral deposits that is found at hydrothermal vents.
Bladder -- a sack in the abdomen that collects urine produced by the kidneys.
Blade -- the flat, green part of a leaf or the expanded or flattened portion of a brown alga.
Blood -- a body fluid that carries food and oxygen to the cells.
Blood plasma -- the liquid, noncellular fraction of blood, including dissolved substances.
Blood pressure -- the force with which blood is pushed against the walls of blood vessels and circulated throughout the body when the heart contracts.
Blood type -- a genetically determined characteristic of human blood; the common blood types are designated a, b, o, ab, rh negative and rh positive.
Bloom -- a dense concentration of phytoplankton that occurs in response to optimum growth conditions.
Blowhole -- the nostrils, or nasal openings, of cetaceans.
Blubber -- the fat found between the skin and muscle of whales and other cetaceans, from which oil is made.
Blue-green algae -- prokaryote organisms with photosynthetic pigments.
B-lymphocytes -- the cells that manufacture antibodies involved in immunity.
Bog -- an area of waterlogged soil that tends to be peaty; fed mainly by precipitation; low productivity; some bogs are acidic.
Bone -- the hard skeletal part of an animal that provides protection and support.
Bony fishes -- fishes with a skeleton made mostly of bone; they also have gill covers.
Boreal -- relating to a northern biotic area characterized by a predominance of coniferous forests and tundra.
Boreal forest -- a broad band of mixed coniferous and deciduous trees that stretches across northern North America (and also Europe and Asia ); its northernmost edge, the taiga, intergrades with the arctic tundra.
Botany -- the study of plants.
Bowels -- the division of the alimentary canal below the stomach.
Brachiopoda -- a phylum of marine animals whose members possess a bivalved calcareous and/or chitinous shell that is secreted by a mantle and encloses nearly all of the body. Unlike the molluscs, the valves are dorsal and ventral. Lampshells.
Brain -- the central organ of the nervous system.
Branchial -- referring to gills.
Breaching -- the process of leaping into the air by whales.
Broadcast spawners -- marine animals that reproduce by releasing eggs and sperm into the water.
Bronchi -- the paired ventilatory tubes of a vertebrate that branch into each lung at the lower end of the trachea.
Bronchitis -- an inflammation of bronchial linings that causes persistent cough, copious production of sputum, and involuntary muscle spasms that constrict airways.
Brood patch -- the patch of feathers used by birds to incubate eggs.
Brooding -- the parental care of developing young.
Brown algae -- seaweeds with a predominance of yellow and brown pigments.
Budding -- a form of asexual reproduction in which new individuals develop from a portion of the parent.
By-catch -- the less valuable catch that is captured while fishing for a more valuable catch.
C
Calcium carbonate -- a mineral that is the major component of the shell, skeleton, and other parts of many organisms.
Calorie -- the amount of heat energy required to raise the temperature of 1g of water 1 degree C.
Cambrian -- a geological period of the Paleozoic beginning about 590 million years ago and lasting about 85 million years, during which time many divisions of protists occurred in the oceans.
Campestral -- a characteristic of rural locations, especially open country and grasslands.
Cancer -- invasive, out-of-control cell growth that results in malignant tumors.
Canine -- relating to, affecting, resembling or derived from a dog .
Canopy -- the upper portion of a population of plants; the term is usually associated with forests and agricultural crops.
Capillary -- a fine blood vessel which carries blood to cells.
Captive breeding -- raising plants or animals in zoos or other controlled conditions to produce stock for subsequent release into the wild.
Carbohydrate -- compounds of carbon, hydrogen, and oxygen that provide a structural component of living cells and a source of energy for animals in the form of sugars.
Carbon -- an element that is an essential constituent of all organic compounds.
Carbon dating -- a procedure used to determine the age of fossils.
Carbon dioxide -- a colorless gas that is required in the process of photosynthesis.
Carbonic acid -- atmospheric co 2 dissolved in water to yield h 2 co 3 , a weak acid.
Carboniferous -- a geological period of the Paleozoic beginning approximately 360 million years ago and lasting about 85 million years. During this time forests appeared and became dominant, composed of arborescent club mosses, horsetails, and ferns. Their extinction resulted in the formation of coal deposits.
Carcinogens -- substances that cause cancer.
Cardiac -- belonging or relating to the heart.
Carnivore -- any organism that eats animals.
Carpal -- the wrist.
Carrying capacity -- the maximum number of a population that can be supported by the environment over a given period of time.
Cartilage -- a spongy tissue that covers the ends of the bones where they come together making a joint.
Cartilaginous fishes (class Chondrichthyes) -- fishes with a skeleton made of cartilage: sharks, rays, skates, and ratfishes (or chimaeras).
Cash crops -- crops that are sold rather than consumed or bartered.
Caste -- one of the polymorphic forms within an insect society, each caste having its specific duties, as queen, worker, soldier, and so on.
Catabolic -- chemical reactions that release energy by degrading complex compounds into simpler ones.
Catadromous -- refers to fishes that migrate from fresh water to the ocean to spawn.
Caudal -- constituting, belonging to, or relating to a tail.
Caudal (posterior) -- toward the south wall or butt.
Cell -- minute biological compartments within which the processes of life are carried out.
Cellular respiration -- the process in which a cell breaks down sugar or other organic compounds to release energy used for cellular work; may be anaerobic or aerobic, depending on the availability of oxygen.
Cellulose -- the chief polysaccharide constituent of the cell wall of green plants and some fungi; an insoluble carbohydrate that is converted into glucose.
Cenozoic -- a geological era beginning 65 million years ago and extending to the present, characterized by major adaptive radiation of specialized life forms and formation of biomes.
Central vacuole -- a membrane-enclosed sac that takes up most of the volume of a mature plant cell.
Cephalaspidomorphi -- the class of vertebrates characterized by the absence of paired appendages and the presence of sucking mouthparts with teeth and a rasping tongue. Lampreys.
Cephalochordata -- the subphylum of chordates whose members possess a laterally compressed, transparent body. They are fishlike and possess all four chordate characteristics throughout life. Amphioxus.
Cephalopods (class Cephalopoda) -- octopuses, squids, and other molluscs that possess a foot modified into arms that surround the head.
Cephalothorax -- a body division found in many Arachnida and higher crustacea, in which the head is fused with some or all of the thoracic segments.
Cereals -- members of the grass family that yield a large amount of grain rich in carbohydrates, fats, proteins, and vitamins.
Cerebellum -- the lower part of the brain that coordinates and control skeletal muscle movement.
Cerebrum -- the largest part of the mammalian brain that occupies the dome of the cranium.
Cervical -- relating to a neck.
Cervical vertebrae -- the seven vertebrae closest to the skull.
Cestoidea -- the class of platyhelminthes that has members that are all parasitic with no digestive tract; have great reproductive potentials. Tapeworms.
Cetaceans (order Cetacea) -- marine mammals with anterior flippers, no posterior limbs, and a dorsal fin. Whales, dolphins, and porpoises.
Chaparral -- a relatively dry biome that occurs in the southwestern United States .
Character -- any well-defined feature, whether anatomical, behavioral, biochemical, or genomic, of an organism.
Chelicerata -- the subphylum of arthropods whose members have a body that is divided into prosoma and opisthoma. The first pair of appendages are feeding appendages called chelicerae. Spiders, scorpions, mites, and ticks.
Chemoreceptor -- a receptor that is stimulated by the presence of certain chemical substances.
Chemosynthesis -- autotrophic synthesis of organic compounds by certain bacteria; uses energy from inorganic compounds.
Chemotroph -- an organism that derives nourishment from inorganic substances without using chlorophyll.
Chigger -- a parasitic mite of the family Trombiculidae.
Chinampas -- long, narrow strips of land bordered on three sides by irrigation canals which can produce several crops per year.
Chlorofluorocarbons (cfcs) -- chemicals used in sprays and other products that affect the ozone layer.
Chlorophyll -- the green pigment found in plants and in some animals; necessary for photosynthesis.
Chloroplast -- a plastid containing chlorophyll and usually other pigments, found in cytoplasm of plant cells.
Cholesterol -- a steroid that is an integral part of cell membranes and a precursor to other steroidal compounds in animals.
Chondrichthyes -- the class of vertebrates whose members are fishlike, possess paired appendages and a cartilaginous skeleton, and lack a swim bladder. Skates, rays, and sharks.
Chordata -- a phylum of animals whose members are characterized by a notochord, pharyngeal gill slits, a dorsal tubular nerve cord, and a postanal tail.
Chromoplast -- membrane-bound organelle containing pigments other than chlorophyll; the pigments may be yellow, orange, or red.
Chromosome -- a rod-like structure that appears in the nucleus of a cell during mitosis; contains the genes responsible for heredity.
Chrysalis -- the pupal case of a butterfly that forms from the exoskeleton of the larva.
Ciguatera -- a type of poisoning found in tropical fishes. It may result from a toxin produced by a dinoflagellate.
Cilium (pl. Cilia) --a short, hair-like flagellum that is found in large numbers and used in movement, for pushing food particles, and in other functions.
Circadian -- occurring at a period of approximately 24 hours.
Circadian rhythms -- daily cycles of activity.
Circulatory system -- pertaining to the circulation. Also cardiovascular system.
City -- a differentiated community with a sufficient population and resource base to allow residents to specialize in arts, crafts, services, and professional occupations.
Clade -- a taxon or other group consisting of an ancestral species and all of its descendants, forming a distinct branch on a phylogenetic tree.
Cladistics -- a system of arranging taxa by analysis of evolutionarily derived characteristics so that the arrangement will reflect phylogenetic relationships.
Clasper -- a copulatory organ along the inner edge of each pelvic fin in male sharks and other cartilaginous fishes.
Class -- taxonomic rank consisting of related orders.
Clavicle (collarbone) -- a long bone which lies almost horizontally at the root of the neck.
Claw -- the sharp, usually curved, nail on the foot of an animal or insect. The pincer-like extremity of specific limbs of certain arthropods (e.g., lobster claws).
Clear-cut -- cutting every tree in a given area, regardless of species or size; an appropriate harvest method for some species; can be destructive if not carefully controlled.
Climate -- a description of the long-term pattern of weather in a particular area.
Climatology -- the study of climates and the factors influencing them.
Cloaca -- the posterior chamber of digestive tract in many vertebrates, receiving feces and urogenital products. In certain invertebrates, a terminal portion of digestive tract that serves also as respiratory, excretory, or reproductive tract.
Clone -- a series of identical cells or individuals that have developed from a single cell or individual.
Closed canopy -- a forest where tree crowns spread over 20 percent of the ground.
Cloud forests -- high mountain forests where temperatures are uniformly cool and fog or mist keeps vegetation wet all the time.
Cnidaria -- the phylum of animals whose members are characterized by radial or biradial symmetry, diploblastic organization, a gastrovascular cavity, and nematocysts. Jellyfish, sea anemones, and their relatives.
Coagulation -- a process in which a series of enzymes are activated, resulting in clotting of blood.
Coal washing -- coal technology that involves crushing coal and washing out soluble sulfur compounds with water or other solvents.
Coccus -- any of various spherical-shaped bacteria.
Coccyx (tailbone) -- the bone at the apex of the sacrum of anthropoids. It is usually comprised of 4 vertebrae fused together.
Cochlea -- a tubular cavity of the inner ear containing the essential organs of hearing; occurs in crocodiles, birds, and mammals; spirally coiled in mammals.
Cocoon -- a protective covering of a resting or developmental stage, sometimes used to refer to both the covering and its contents; for example, the cocoon of a moth or the protective covering for the developing embryos in some annelids.
Coelacanths -- a group of lobed-fin fossil fishes. Latimeria was discovered alive in 1952.
Coenose -- an assemblage of fossils.
Cognition -- the processes in the minds of animals or their general mental functions, including perception, representation, and memory.
Colon -- the large intestine.
Colonization -- the pioneer establishment of vegetation on a previously unvegetated area.
Commensalism -- a relationship in which one individual lives close to or on another and benefits, and the host is unaffected.
Common ancestor -- the hypothetical single species of organisms that two or more different species of organisms evolved from.
Communal nesting -- more than one female in a nest raising the young of more than one female.
Communication -- an act on the part of one organism (or cell) that alters the probability of patterns of behavior in another organism (or cell) in an adaptive fashion.
Community -- the combined populations of organisms in a given area.
Comparative anatomy -- the study of animal structure in an attempt to deduce evolutionary pathways in particular animal groups.
Competition -- an overlap of ecological niches where two populations in the same community depend on the same food source, shelter, or other resources.
Compost -- partially decayed organic matter used in gardening and farming to enrich the soil and increase water holding capacity.
Composting -- the biological degradation of organic material under aerobic (oxygen-rich) conditions to produce compost, a nutrient-rich soil amendment and conditioner.
Compound eye -- an eye consisting of many individual lens systems. Present in many members of the phylum Arthropoda.
Compound fruit -- a fruit consisting of several individual fruits held together (pineapple) or in which separate carpels of a flower stay together (blackberry).
Compound leaf -- a leaf composed of two or more completely independent blade units called leaflets.
Compression -- a fossil formed when carbonized plant material is still present in the original shape but is greatly compressed and reduced in size by pressure.
Conditioning -- a form of learning in which a behavior is associated with a reward such as food.
Coniferous forest -- a community type dominated by cone-bearing gymnosperms mostly in the northern hemisphere.
Conifers -- needle-bearing trees that produce seeds in cones.
Connective tissue -- a basic type of tissue that includes bone, cartilage, and various fibrous tissues.
Conservation -- to protect, conserve the natural world and all its components.
Consumer -- a heterotroph.
Contagious -- capable of being transmitted through direct contact.
Continuous feeder -- usually slow-moving sessile animals that feed all of the time.
Contour feathers -- feathers that cover the body, wings, and tail of a bird. Contour feathers provide flight surfaces and are responsible for plumage colors.
Contour plowing -- plowing along hill contours to reduce erosion.
Control group -- an observed, unmanipulated set of test subjects.
Control -- that part of a scientific experiment to which the experimental variable is not applied but which is similar to the experimental group in all other respects.
Convergent -- describes characters that are similar in structure and function but have arisen separately rather than from a common ancestor. Convergence is common in groups that become adapted to a similar habitat or way of life; the similar body shapes of the North American gray wolf and the Tasmanian wolf, each evolving from different ancestors (the former is a placental mammal, the latter is a marsupial mammal), resulted from secondary adaptation to similar habitats.
Cool deserts -- deserts such as the American great basin characterized by cold winters and sagebrush.
Cooperative breeding -- a breeding system in which non-parents share in rearing the young.
Copepods -- small, mostly planktonic crustaceans.
Coprolite -- fossilized fecal material.
Copulation -- sexual union to facilitate the reception of sperm by the female.
Coral reefs -- prominent oceanic features composed of hard, limy skeletons produced by coral animals.
Core area -- the area of heaviest use within the home range.
Coriolis Effect -- the apparent change in direction of a moving object (to the left in the southern hemisphere and to the right in the northern hemisphere) due to the rotation of the earth.
Cornea -- the outer transparent coat of the eye.
Corolla -- the collective term for the petals of a flower.
Corona -- a crown or encircling structure.
Coronary -- encircling as a crown. 1. Vessels encircling the heart. 2. A condition caused by a decreased blood flow to the heart muscle.
Corridor -- a strip of natural habitat that connects two adjacent nature preserves to allow migration of organisms from one place to another.
Cortisone -- an animal hormone not synthesized by plants.
Cosmopolitan -- worldwide in distribution.
Costal cartilages -- bars of hyaline cartilage which extend forwards from the anterior ends of the ribs and contribute to the elasticity of the thorax.
Cotyledon -- a seed leaf; the first leaf formed in a seed.
Counterillumination -- the emission of light by mid-water animals to match the background light.
Countershading -- contrasting coloration that helps conceal the animal (e.g., the darkly pigmented top and lightly pigmented bottom of frogs).
Coursers -- predators that chase their prey over long distances.
Courtship behavior -- a behavior related to the attraction of the opposite sex and mating.
Cover crops -- plants, such as rye, alfalfa, or clover that can be planted immediately after harvest to hold and protect the soil.
Cranial, or anterior -- toward the north wall or head.
Crepuscular -- daily cycles with peak activity around dusk and/or dawn.
Crinoidea -- the class of echinoderms whose members are attached by a stalk of ossicles or are free living. Sea lilies and feather stars.
Croplands -- lands used to grow crops.
Cross-pollination -- the transfer of pollen from the stamen to the stigma of a flower of another plant.
Crown -- the topmost portion of a plant.
Crustacea -- the subphylum of mandibulate arthropods whose members are characterized by having two pairs of antennae, one pair of mandibles, two pairs of maxillae, and biramous appendages. Crabs, crayfish, lobsters.
Cursorial -- describes an animal built for rapid terrestrial locomotion.
Cuticle -- a protective layer secreted by the hypodermis of many invertebrates, the outside layer of skinin higher animals, or the waterproof layer of cutin on leaves and non-woody stems.
Cycads -- members of the Cycadophyta, which have unbranched stems and a terminal grouping of leathery, compound leaves.
Cycle -- repeating units that make up the pattern of biological rhythms.
Cyst -- a secreted covering that protects many small invertebrates, including some protozoans, rotifers, and nematodes, from environmental stresses, such as desiccation and overcrowding. In diatoms, a resistant and photosynthetically inactive cell.
D
Dactylozooid -- a polyp of a colonial hydroid specialized for defense or killing food.
Decapods -- crustaceans with five pairs of walking legs and a well-developed carapace. The group includes the shrimps, lobsters, hermit crabs, and crabs.
Deciduous -- referring to plants that lose all their leaves during the cool season.
Deciduous forest -- a forest biome in which the dominant trees are deciduous.
Decomposer -- bacteria and fungi that obtain organic nutrients by breaking down the remains or products of other organic compounds.
Decongestant -- an agent that relieves nasal or respiratory congestion.
Delta -- a fan-shaped sediment deposit found at the mouth of a river.
Deltoid -- a triangular muscle in the shoulder used to lift the upper arm.
Demand -- the amount of a product that consumers are willing and able to buy at various possible prices.
Demersal fish -- a bottom-dwelling fish.
Demography -- the 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 conditions.
Dendrochronology -- the science of studying growth rings of trees to determine past conditions.
Dendroclimatology -- the s tudy of the annual rings of trees in order to interpret climatic changes in the past.
Dengue -- a virus or disease transmitted by mosquitoes.
Denticles -- small, tooth-like projections.
Dependent variable -- what may change (e.g., aggression) in response to manipulation of an independent variable (e.g., food supply) by the experimenter.
Depressant -- a psychoactive drug that has a sedative effect on the central nervous system.
Derived -- describes a character or group of characters that has changed from its primitive state; advanced.
Dermal -- pertaining to the skin.
Dermal tissue -- the tissue that covers surfaces in plants.
Dermatitis -- an infection or inflammation of the skin.
Dermatophytes -- certain imperfect fungi that cause skin diseases in humans; includes the organisms causing ringworm and athlete's foot.
Dermis -- the layer of the skin deep to the epidermis, consisting of a dense bed of vascular connective tissue.
Desalinization (desalination) -- the removal of salt from water by distillation, freezing, or ultrafiltration.
Descendant -- describes a species or taxon that has evolved from another species or from within a taxon.
Desert -- a type of biome characterized by low moisture levels (below 25 cm per year), and infrequent and unpredictable precipitation.
Desertification -- a process by which semiarid ecosystems lose productivity because of loss of plant cover, soil erosion, salinization, or waterlogging.
Despot -- a dominant individual that controls resources.
Detritivore -- organisms that consume organic litter, debris, and dung.
Detritus -- dead organic matter and the decomposers that live on it.
Devonian -- a geological period of the Paleozoic era beginning about 400 million years ago. During this period major diversification of the early land plants occurred.
Diabetes -- a condition 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.
Diaphragm -- a large transvers muscle at the base of the thorax used in respiration to draw air into the lungs of mammals.
Diastolic pressure -- the blood pressure measurement during the interval between heartbeats; it is the second number shown in a blood pressure reading.
Diatoms -- unicellular and eukaryotic autotrophs; mostly planktonic.
Dichotomous -- pertaining to the division or forking of a single axis into two branches.
Dicotyledon (dicot) -- a class of angiosperms in which the seedlings typically possess two cotyledons.
Dieback -- a sudden population decline; also called a population crash.
Digestion -- the process by which larger molecules of food substances are broken down into smaller molecules that can be taken up by the digestive system.
Dimorphic -- having more than one form, size, or appearance; usually referring to the difference between males and females of a species.
Dimorphism -- the existence within a species of two distinct forms according to color, sex, size, organ structure, and so on.
Dinoflagellates -- unicellular, eukaryotic, mostly autotrophic organisms with two unequal flagella.
Dinosauria ("fearfully great lizards") -- animals, partly distinguished by a largely to fully open acetabulum, that first evolved in the latter third of the Triassic and was the dominant land animal from the early Jurassic to the end of the cretaceous.
Diplopoda -- 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.
Discontinuous feeder -- 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.
Disease -- a deleterious change in the body's condition in response to destabilizing factors, such as nutrition, chemicals, or biological agents.
Dispersal -- a more or less permanent movement of an individual from an area, such as movement of a juvenile away from its place of birth.
Display -- any behavior pattern especially adapted in physical form or frequency to function as a social signal in communication.
Distal -- away from the body.
Diurnal -- an animal with an activity period during the light portion of the daily cycle.
Diurnal tide -- a tidal pattern with a high and a low tide each day.
Diversity -- the number of species present in a community, as well as the relative abundance of each species.
Diving reflex -- the reflex certain animals have to stay underwater for prolonged periods of time.
Division -- a taxonomic rank that includes related classes.
DNA (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.
Dominance hierarchy -- 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.
Dominant -- (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.
Dormant -- having reduced metabolic and respiratory activity.
Dorsal -- the back of an animal; usually the upper surface; synonymous with posterior for animals that walk upright.
Down feathers -- the insulating f eathers of adult and immature birds.
Down syndrome -- a congenital syndrome including mental retardation, caused by the cells in a person's body having an extra chromosome 21; also called trisomy 21.
Drift net -- a very long fishing net that is allowed to drift for a long time before it is pulled on board.
Drip irrigation -- a method of irrigation that u ses pipe or tubing perforated with very small holes to deliver water one drop at a time directly to the soil around each plant.
Drives -- the specific motivations corresponding to specific needs.
Drought -- an environmental condition in which precipitation is not sufficient to maximize biological productivity.
Duodenum -- the first and shortest portion of the small intestine lying between the pyloric end of the stomach and the jejunum.
Dura Mater -- the membrane that covers the brain.
E
Echinodermata -- the phylum of coelomate animals whose members are pentaradially symmetrical as adults and possess an endoskeleton covered by epithelium and a water-vascular system. Sea stars, sea urchins, sea cucumbers, sea lilies.
Echinoderms -- invertebrates with radial symmetry and a water vascular system.
Echinoidea -- the class of echinoderms whose members are globular or disk shaped, possess moveable spines, and a skeleton of closely fitting plates. Sea urchins and sand dollars.
Echolocation -- a method of locating objects by determining the time it takes for an echo to return and the direction from which it returns. As in bat echolocation.
Ecological development -- a gradual process of environmental modification by organisms.
Ecological niche -- the functional role and position of a species (population) within a community or ecosystem, including what resources it uses, how and when it uses the resources, and how it interacts with other populations.
Ecological succession -- the sequential replacement of one vegetative community by another through a series of stages; succession ends when the climax community is established.
Ecology -- the scientific study of relationships between organisms and their environment. It is concerned with the life histories, distribution, and behavior of individual species as well as the structure and function of natural systems at the level of populations, communities, and ecosystems.
Economic development -- a rise in real income per person; usually associated with new technology that increases productivity or resources.
Economic growth -- an increase in the total wealth of a nation; if population grows faster than the economy, there may be real economic growth, but the share per person may decline.
Economic sanctions -- using the threat or action of withholding food, medical care, or other critical societal needs to force compliance with one's policies.
Ecosystem -- an ecological unit consisting of both the biotic communities and the nonliving (abiotic) environment, which interact to produce a stable system.
Ecotourism -- a combination of adventure travel, cultural exploration, and nature appreciation in wild settings.
Ectoparasite -- parasite that lives on the outer surface of its host.
Ectopic -- an infection in a location other than normal or expected.
Ectoplasm -- the cortex of a cell or that part of cytoplasm just under the cell surface; contrasts with endoplasm.
Ectotherm -- an organism whose internal temperature varies with that of the environment; cold-blooded.
Edema -- the escape of fluid from blood into interstitial space, causing swelling.
Edge effects -- a change in species composition, physical conditions, or other ecological factors at the boundary between two ecosystems. Some organisms flourish at this boundary and benefit from processes such as habitat fragmentation that increase edge area. Other organisms are harmed by increasing edge effects.
Effluent sewerage -- a low-cost alternative sewage treatment for cities in poor countries that combines some features of septic systems and centralized municipal treatment systems. A septic tank near each residence collects and processes solid wastes and must be pumped periodically just like a septic tank while liquid effluent is collected and piped to a central treatment plant. This avoids drainfields in urban areas and yet allows sewer pipes and treatment plants to be downsized, saving money.
Egg -- the middle of three haploid cells at the micropylar end of the embryo sac; when fertilized, it will form the zygote.
El Nino -- a climatic change marked by shifting of a large warm water pool from the western pacific ocean towards the east. Nutrient-rich upwelling currents along the coast of South America are blocked by this sea change and fisheries fail catastrophically. An El Nino event normally is accompanied by droughts in Australia and Southeast Asia together with heavy rain and snow in western North America .
El Nino southern oscillation (ENSO) -- large-scale changes in the normal weather patterns of the pacific basin and adjacent regions. El Nino is a warming of the surface currents in the eastern pacific, only one of the many consequences of ENSO.
Electrical synapse -- a synapse at which local currents resulting from electrical activity flow between the two neurons through gap junctions joining them.
Electrolyte -- a substance that dissociates into ions when fused or in solution and thus becomes capable of conducting electricity; an ionic solute.
Electroreception -- the ability to detect weak electrical fields in the environment.
Electroreceptor -- a receptor that senses changes in an electrical current usually in the surrounding water; also called an ampullary organ.
Elephantiasis -- a disfiguring condition caused by chronic infection with filarial worms W uchereria bancrofti and B rugia malayi .
Elver -- a juvenile eel.
Embryo -- the early developmental stage that, through embryological development, ultimately becomes an adult individual. In plants, that portion of a seed that will form the growing seedling following germination.
Emergent plant community -- a marine plant community in which most leafy growth occurs above sea level.
Emigrate -- to move from one area to another to take up residence.
Emission standards -- regulations for restricting the amounts of air pollutants that can be released from specific point sources.
Emphysema -- an irreversible, obstructive lung disease in which airways become permanently constricted and alveoli are damaged or destroyed.
Encephalitis -- an infection of the brain, especially by viruses or amoebas.
Endangered species -- a living species that is in danger of becoming extinct because of small population sizes, poor reproduction, reduced available habitat, or a combination of these factors.
Endemic -- native to a certain region or country.
Endocrine -- a system of ductless glands secreting hormones into the bloodstream and targeting another organ to produce a response.
Endocrinology -- the study of the endocrine system and its role in the physiology of an animal.
Endometrium -- the lining of the uterus; during the reproductive years, this layer is sloughed each month during menstruation.
Endoparasite -- a parasite that lives inside its host.
Endophyte -- a plant that lives within the tissues of another plant.
Endoplasm -- the portion of cytoplasm that immediately surrounds the nucleus.
Endotherm -- an organism that can regulate its internal temperature; warm-blooded.
Energy pyramid -- a representation of the loss of useful energy at each step in a food chain.
Enteron -- the digestive cavity.
Entomology -- the study of insects.
Entozoic -- living within another animal; internally parasitic.
Environment -- the circumstances or conditions that surround an organism or group of organisms as well as the complex of social or cultural conditions that affect an individual or community.
Environmental ethics -- a search for moral values and ethical principles in human relations with the natural world.
Environmental impact statement (EIS) -- an analysis, required by provisions in the national environmental policy act of 1970, of the effects of any major program a federal agency plans to undertake.
Environmental resistance -- all of the limiting factors that tend to reduce population growth rates and set the maximum allowable population size or carrying capacity of an ecosystem.
Environmental resources -- anything an organism needs that can be taken from the environment.
Environmental science -- the systematic, scientific study of our environment and our role in it.
Environmental terrorism -- conducting acts of terrorism through the destruction or pollution of the environment.
Environmentalism -- active participation in attempts to solve environmental pollution and resource problems.
Enzymes -- molecules, usually proteins or nucleic acids, which act as catalysts in biochemical reactions.
Epi -- a prefix meaning on, upon, or over.
Epidemic -- a sharp rise in the incidence of an infection or disease.
Epidemiology -- the study of the distribution and causes of disease and injuries in human populations.
Epidermis -- the outer, nonvascular layer of skin.
Epiphyte -- a plant that grows on top of another plant for support and position, but derives no nutrition from the host.
Epizootic -- a massive infection rate among animals other than humans; identical to an epidemic in humans.
Equatorial currents -- major ocean currents that move parallel to the equator.
Erythrocyte -- a red blood cell; has hemoglobin to carry oxygen from lungs or gills to tissues; during formation in mammals, erythrocytes lose their nuclei, those of other vertebrates retain the nuclei.
Esophagus -- the passage extending from the pharynx to the stomach.