Biota: The spectrum of different living organisms inhabiting a particular region, habitat, or biotope.Biodiversity: The variety of all native living organisms and their various forms and interrelationships.Ecosystem: A functional system which includes the organisms of a natural community together with their environment. (McGraw Hill Dictionary of Scientific and Technical Terms, 4th ed)Thuja: A plant genus of the family CUPRESSACEAE.Fossils: Remains, impressions, or traces of animals or plants of past geological times which have been preserved in the earth's crust.Geology: The science of the earth and other celestial bodies and their history as recorded in the rocks. It includes the study of geologic processes of an area such as rock formations, weathering and erosion, and sedimentation. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Invertebrates: Animals that have no spinal column.Soil: The unconsolidated mineral or organic matter on the surface of the earth that serves as a natural medium for the growth of land plants.Oceans and Seas: A great expanse of continuous bodies of salt water which together cover more than 70 percent of the earth's surface. Seas may be partially or entirely enclosed by land, and are smaller than the five oceans (Atlantic, Pacific, Indian, Arctic, and Antarctic).Paleontology: The study of early forms of life through fossil remains.Geological Processes: Events and activities of the Earth and its structures.Geological Phenomena: The inanimate matter of Earth, the structures and properties of this matter, and the processes that affect it.Geography: The science dealing with the earth and its life, especially the description of land, sea, and air and the distribution of plant and animal life, including humanity and human industries with reference to the mutual relations of these elements. (From Webster, 3d ed)Zooplankton: Minute free-floating animal organisms which live in practically all natural waters.Rivers: Large natural streams of FRESH WATER formed by converging tributaries and which empty into a body of water (lake or ocean).Marine Biology: The study of the origin, structure, development, growth, function, genetics, and reproduction of organisms which inhabit the OCEANS AND SEAS.Ageratina: A plant genus of the family ASTERACEAE. The common name of snakeroot is also used for POLYGALA; SANICULA; ARISTOLOCHIA and others.Fagus: A plant genus of the family FAGACEAE.Water Pollutants, Chemical: Chemical compounds which pollute the water of rivers, streams, lakes, the sea, reservoirs, or other bodies of water.Biological Evolution: The process of cumulative change over successive generations through which organisms acquire their distinguishing morphological and physiological characteristics.Aquatic Organisms: Organisms that live in water.Introduced Species: Non-native organisms brought into a region, habitat, or ECOSYSTEM by human activity.Fresh Water: Water containing no significant amounts of salts, such as water from RIVERS and LAKES.Population Dynamics: The pattern of any process, or the interrelationship of phenomena, which affects growth or change within a population.Ice Cover: A thick mass of ICE formed over large regions of land; RIVERS; LAKES; ponds; or SEAWATER.Food Chain: The sequence of transfers of matter and energy from organism to organism in the form of FOOD. Food chains intertwine locally into a food web because most organisms consume more than one type of animal or plant. PLANTS, which convert SOLAR ENERGY to food by PHOTOSYNTHESIS, are the primary food source. In a predator chain, a plant-eating animal is eaten by a larger animal. In a parasite chain, a smaller organism consumes part of a larger host and may itself be parasitized by smaller organisms. In a saprophytic chain, microorganisms live on dead organic matter.Oligochaeta: A class of annelid worms with few setae per segment. It includes the earthworms such as Lumbricus and Eisenia.Animal Shells: The hard rigid covering of animals including MOLLUSCS; TURTLES; INSECTS; and crustaceans.Geologic Sediments: A mass of organic or inorganic solid fragmented material, or the solid fragment itself, that comes from the weathering of rock and is carried by, suspended in, or dropped by air, water, or ice. It refers also to a mass that is accumulated by any other natural agent and that forms in layers on the earth's surface, such as sand, gravel, silt, mud, fill, or loess. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed, p1689)Seawater: The salinated water of OCEANS AND SEAS that provides habitat for marine organisms.Environmental Monitoring: The monitoring of the level of toxins, chemical pollutants, microbial contaminants, or other harmful substances in the environment (soil, air, and water), workplace, or in the bodies of people and animals present in that environment.Bryozoa: A phylum of small sessile aquatic animals living as small tufted colonies. Some appear like hydroids or corals, but their internal structure is more advanced. Most bryozoans are matlike, forming thin encrustations on rocks, shells, or kelp. (Storer & Stebbins, General Zoology, 6th ed, p443)Phylogeny: The relationships of groups of organisms as reflected by their genetic makeup.Soil Microbiology: The presence of bacteria, viruses, and fungi in the soil. This term is not restricted to pathogenic organisms.Water Pollution, Chemical: Adverse effect upon bodies of water (LAKES; RIVERS; seas; groundwater etc.) caused by CHEMICAL WATER POLLUTANTS.Phylogeography: A field of study concerned with the principles and processes governing the geographic distributions of genealogical lineages, especially those within and among closely related species. (Avise, J.C., Phylogeography: The History and Formation of Species. Harvard University Press, 2000)Trees: Woody, usually tall, perennial higher plants (Angiosperms, Gymnosperms, and some Pterophyta) having usually a main stem and numerous branches.Desert Climate: A type of climate characterized by insufficient moisture to support appreciable plant life. It is a climate of extreme aridity, usually of extreme heat, and of negligible rainfall. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Plants: Multicellular, eukaryotic life forms of kingdom Plantae (sensu lato), comprising the VIRIDIPLANTAE; RHODOPHYTA; and GLAUCOPHYTA; all of which acquired chloroplasts by direct endosymbiosis of CYANOBACTERIA. They are characterized by a mainly photosynthetic mode of nutrition; essentially unlimited growth at localized regions of cell divisions (MERISTEMS); cellulose within cells providing rigidity; the absence of organs of locomotion; absence of nervous and sensory systems; and an alternation of haploid and diploid generations.Antarctic Regions: The continent lying around the South Pole and the southern waters of the Atlantic, Pacific, and Indian Oceans. It includes the Falkland Islands Dependencies. (From Webster's New Geographical Dictionary, 1988, p55)Wetlands: Environments or habitats at the interface between truly terrestrial ecosystems and truly aquatic systems making them different from each yet highly dependent on both. Adaptations to low soil oxygen characterize many wetland species.Bivalvia: A class in the phylum MOLLUSCA comprised of mussels; clams; OYSTERS; COCKLES; and SCALLOPS. They are characterized by a bilaterally symmetrical hinged shell and a muscular foot used for burrowing and anchoring.Conservation of Natural Resources: The protection, preservation, restoration, and rational use of all resources in the total environment.Climate: The longterm manifestations of WEATHER. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Extinction, Biological: The ceasing of existence of a species or taxonomic groups of organisms.Hydrothermal Vents: Hot springs on the ocean floor. They are commonly found near volcanically active places such as mid-oceanic ridges.Biomass: Total mass of all the organisms of a given type and/or in a given area. (From Concise Dictionary of Biology, 1990) It includes the yield of vegetative mass produced from any given crop.Arthropods: Members of the phylum Arthropoda, composed of organisms having a hard, jointed exoskeleton and paired jointed legs. It includes the class INSECTS and the subclass ARACHNIDA, many species of which are important medically as parasites or as vectors of organisms capable of causing disease in man.Phytoplankton: Free-floating minute organisms that are photosynthetic. The term is non-taxonomic and refers to a lifestyle (energy utilization and motility), rather than a particular type of organism. Most, but not all, are unicellular algae. Important groups include DIATOMS; DINOFLAGELLATES; CYANOBACTERIA; CHLOROPHYTA; HAPTOPHYTA; CRYPTOMONADS; and silicoflagellates.Ecology: The branch of science concerned with the interrelationship of organisms and their ENVIRONMENT, especially as manifested by natural cycles and rhythms, community development and structure, interactions between different kinds of organisms, geographic distributions, and population alterations. (Webster's, 3d ed)Fishes: A group of cold-blooded, aquatic vertebrates having gills, fins, a cartilaginous or bony endoskeleton, and elongated bodies covered with scales.Global Warming: Increase in the temperature of the atmosphere near the Earth's surface and in the troposphere, which can contribute to changes in global climate patterns.Mercury: A silver metallic element that exists as a liquid at room temperature. It has the atomic symbol Hg (from hydrargyrum, liquid silver), atomic number 80, and atomic weight 200.59. Mercury is used in many industrial applications and its salts have been employed therapeutically as purgatives, antisyphilitics, disinfectants, and astringents. It can be absorbed through the skin and mucous membranes which leads to MERCURY POISONING. Because of its toxicity, the clinical use of mercury and mercurials is diminishing.History, Ancient: The period of history before 500 of the common era.Tropical Climate: A climate which is typical of equatorial and tropical regions, i.e., one with continually high temperatures with considerable precipitation, at least during part of the year. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Water Pollutants: Substances or organisms which pollute the water or bodies of water. Use for water pollutants in general or those for which there is no specific heading.Climate Change: Any significant change in measures of climate (such as temperature, precipitation, or wind) lasting for an extended period (decades or longer). It may result from natural factors such as changes in the sun's intensity, natural processes within the climate system such as changes in ocean circulation, or human activities.Poaceae: A large family of narrow-leaved herbaceous grasses of the order Cyperales, subclass Commelinidae, class Liliopsida (monocotyledons). Food grains (EDIBLE GRAIN) come from members of this family. RHINITIS, ALLERGIC, SEASONAL can be induced by POLLEN of many of the grasses.Atlantic OceanSpecies Specificity: The restriction of a characteristic behavior, anatomical structure or physical system, such as immune response; metabolic response, or gene or gene variant to the members of one species. It refers to that property which differentiates one species from another but it is also used for phylogenetic levels higher or lower than the species.Arctic Regions: The Arctic Ocean and the lands in it and adjacent to it. It includes Point Barrow, Alaska, most of the Franklin District in Canada, two thirds of Greenland, Svalbard, Franz Josef Land, Lapland, Novaya Zemlya, and Northern Siberia. (Webster's New Geographical Dictionary, 1988, p66)Atmosphere: The gaseous envelope surrounding a planet or similar body. (From Random House Unabridged Dictionary, 2d ed)Greenhouse Effect: The effect of GLOBAL WARMING and the resulting increase in world temperatures. The predicted health effects of such long-term climatic change include increased incidence of respiratory, water-borne, and vector-borne diseases.Endangered Species: An animal or plant species in danger of extinction. Causes can include human activity, changing climate, or change in predator/prey ratios.Methylmercury Compounds: Organic compounds in which mercury is attached to a methyl group.Flame Retardants: Materials applied to fabrics, bedding, furniture, plastics, etc. to retard their burning; many may leach out and cause allergies or other harm.Bacteria: One of the three domains of life (the others being Eukarya and ARCHAEA), also called Eubacteria. They are unicellular prokaryotic microorganisms which generally possess rigid cell walls, multiply by cell division, and exhibit three principal forms: round or coccal, rodlike or bacillary, and spiral or spirochetal. Bacteria can be classified by their response to OXYGEN: aerobic, anaerobic, or facultatively anaerobic; by the mode by which they obtain their energy: chemotrophy (via chemical reaction) or PHOTOTROPHY (via light reaction); for chemotrophs by their source of chemical energy: CHEMOLITHOTROPHY (from inorganic compounds) or chemoorganotrophy (from organic compounds); and by their source for CARBON; NITROGEN; etc.; HETEROTROPHY (from organic sources) or AUTOTROPHY (from CARBON DIOXIDE). They can also be classified by whether or not they stain (based on the structure of their CELL WALLS) with CRYSTAL VIOLET dye: gram-negative or gram-positive.Eukaryota: One of the three domains of life (the others being BACTERIA and ARCHAEA), also called Eukarya. These are organisms whose cells are enclosed in membranes and possess a nucleus. They comprise almost all multicellular and many unicellular organisms, and are traditionally divided into groups (sometimes called kingdoms) including ANIMALS; PLANTS; FUNGI; and various algae and other taxa that were previously part of the old kingdom Protista.LizardsGenetic Speciation: The splitting of an ancestral species into daughter species that coexist in time (King, Dictionary of Genetics, 6th ed). Causal factors may include geographic isolation, HABITAT geometry, migration, REPRODUCTIVE ISOLATION, random GENETIC DRIFT and MUTATION.Environment: The external elements and conditions which surround, influence, and affect the life and development of an organism or population.Snails: Marine, freshwater, or terrestrial mollusks of the class Gastropoda. Most have an enclosing spiral shell, and several genera harbor parasites pathogenic to man.Environmental Pollutants: Substances or energies, for example heat or light, which when introduced into the air, water, or land threaten life or health of individuals or ECOSYSTEMS.North AmericaBirds: Warm-blooded VERTEBRATES possessing FEATHERS and belonging to the class Aves.DNA, Mitochondrial: Double-stranded DNA of MITOCHONDRIA. In eukaryotes, the mitochondrial GENOME is circular and codes for ribosomal RNAs, transfer RNAs, and about 10 proteins.Population Density: Number of individuals in a population relative to space.Fungi: A kingdom of eukaryotic, heterotrophic organisms that live parasitically as saprobes, including MUSHROOMS; YEASTS; smuts, molds, etc. They reproduce either sexually or asexually, and have life cycles that range from simple to complex. Filamentous fungi, commonly known as molds, refer to those that grow as multicellular colonies.Animal Migration: Periodic movements of animals in response to seasonal changes or reproductive instinct. Hormonal changes are the trigger in at least some animals. Most migrations are made for reasons of climatic change, feeding, or breeding.DNA, Ribosomal: DNA sequences encoding RIBOSOMAL RNA and the segments of DNA separating the individual ribosomal RNA genes, referred to as RIBOSOMAL SPACER DNA.Vertebrates: Animals having a vertebral column, members of the phylum Chordata, subphylum Craniata comprising mammals, birds, reptiles, amphibians, and fishes.Seasons: Divisions of the year according to some regularly recurrent phenomena usually astronomical or climatic. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Asia: The largest of the continents. It was known to the Romans more specifically as what we know today as Asia Minor. The name comes from at least two possible sources: from the Assyrian asu (to rise) or from the Sanskrit usa (dawn), both with reference to its being the land of the rising sun, i.e., eastern as opposed to Europe, to the west. (From Webster's New Geographical Dictionary, 1988, p82 & Room, Brewer's Dictionary of Names, 1992, p34)RNA, Ribosomal, 16S: Constituent of 30S subunit prokaryotic ribosomes containing 1600 nucleotides and 21 proteins. 16S rRNA is involved in initiation of polypeptide synthesis.Temperature: The property of objects that determines the direction of heat flow when they are placed in direct thermal contact. The temperature is the energy of microscopic motions (vibrational and translational) of the particles of atoms.EuropeModels, Biological: Theoretical representations that simulate the behavior or activity of biological processes or diseases. For disease models in living animals, DISEASE MODELS, ANIMAL is available. Biological models include the use of mathematical equations, computers, and other electronic equipment.Sequence Analysis, DNA: A multistage process that includes cloning, physical mapping, subcloning, determination of the DNA SEQUENCE, and information analysis.Nitrogen: An element with the atomic symbol N, atomic number 7, and atomic weight [14.00643; 14.00728]. Nitrogen exists as a diatomic gas and makes up about 78% of the earth's atmosphere by volume. It is a constituent of proteins and nucleic acids and found in all living cells.Water: A clear, odorless, tasteless liquid that is essential for most animal and plant life and is an excellent solvent for many substances. The chemical formula is hydrogen oxide (H2O). (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)China: A country spanning from central Asia to the Pacific Ocean.Evolution, Molecular: The process of cumulative change at the level of DNA; RNA; and PROTEINS, over successive generations.Molecular Sequence Data: Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.Carbon Dioxide: A colorless, odorless gas that can be formed by the body and is necessary for the respiration cycle of plants and animals.BrazilModels, Theoretical: Theoretical representations that simulate the behavior or activity of systems, processes, or phenomena. They include the use of mathematical equations, computers, and other electronic equipment.Adaptation, Physiological: The non-genetic biological changes of an organism in response to challenges in its ENVIRONMENT.