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An ongoing current event in which a large number of living species are threatened with extinction or are going extinct because of environmentally destructive human activities. The Earth is presently in the midst of a mass extinction event. In the…

Any of several leguminous plants, or their seeds, long utilized as food by humans or livestock. There are more than 40,000 varieties of beans, with only a small number of these being mass-produced for human or animal consumption. In particular,…

The response of corals to environmental stress in which they eject the single-cell algae that live within the transparent coral tissue, making the white coral skeleton visible. Corals (Fig. 1) are animals that live in a partnership (symbiosis) with…

Marine animal life inhabiting the portion of the oceans below the upper limit of the continental slopes. The marine animals that make up the deep-sea fauna live below the photic zone of the oceans. In general, the deep sea may be regarded as that…

A species translocated from one region or continent to another outside its normal range, particularly when the translocation is the result of human activity (intentional or otherwise). Many thousands of species, including animals, plants, fungi,…

A natural process in which harmful or beneficial effects are caused by secondary metabolites that spread from a donor organism to a recipient and are produced by plants, algae, bacteria, and fungi. Allelopathy is a key ecological process and has…

A discipline within the field of animal behavior that focuses on the reception and use of signals. Animal communication could well include all of animal behavior because a liberal definition of the term signal could encompass all stimuli perceived…

The scientific study of past material culture. The initial objective of archeology (often spelled archaeology) is to construct cultural chronologies that order past material culture into meaningful temporal segments. The intermediate objective is to…

The study of behavior change in response to drugs, chemicals, or other environmental conditions or agents. Behavioral toxicology investigates the effect of toxic exposure on organismal behavior. The toxic exposure can involve various chemicals,…

The destruction of organic compounds by microorganisms. Biodegradation is a process (carried out by microorganisms) that decomposes organic material into its constituent elements or new compounds. Microorganisms, particularly bacteria (and fungi to…

A microbial (often bacterial) community that is enveloped by an adhesive substance (the glycocalyx) at the interface of a liquid and a surface. Biofilms (see illustration) are defined as highly structured communities of microorganisms that are…

The study of the cycling of chemicals between organisms and the surface environment of the Earth. The chemicals either can be taken up by organisms and used for growth and synthesis of living matter or can be processed to obtain energy. The chemical…

The use of parasitoids, predators, and pathogens to reduce injurious pest insect populations and consequently the damage that they cause. Biological insect control (or insect biocontrol) is the regulation of insect populations by biological means.…

Management of the human use of natural resources to provide the maximum benefit to current generations while maintaining capacity to meet the needs of future generations. Conservation includes both the protection and rational use of natural…

Pathological conditions affecting the health of coral and causing its physiological dysfunction. Broadly defined, coral disease (Fig. 1) is any impairment to coral health resulting in physiological disturbance and breakdown. It usually involves…

A measure of the three-dimensional structure of live coral communities on reefs. Coral reef structural complexity is an intrinsic element of coral reef ecosystems and quantitates the surface area of coral in relation to its linear area. The…

A large, tawny brown wild cat, Puma concolor (family Felidae), once widespread over most of the Americas; also known as catamount, mountain lion, painter, and puma. The cougar (Puma concolor; see illustration) is a carnivorous member of the family…

The adaptation of an animal or plant through breeding in captivity to a life intimately associated with and advantageous to humans. Domesticated plants and animals differ genetically and morphologically from their wild counterparts, often in ways…

Plants occupying sand dunes and the slacks, or swales, and flats between them. The density and diversity of dune vegetation are greater on coastal dunes than on desert dunes. Dune Plant geography Sand Zonation A zonation pattern is evident in the…

The earliest representatives of people anatomically similar to living humans that evolved from more archaic humans approximately 150,000–300,000 years ago. The general process by which early modern humans (Homo sapiens) emerged from late archaic…

The biological sonar that bats, toothed whales, and certain other animals use to navigate without the visual system. Echolocation, or biosonar, is the physiological process that certain animals use to locate objects by reflected sound, primarily in…

The interaction of at least two organisms or species such that, for each, the birth or growth rates are depressed and the death rate increased by the presence of the other organisms or species. Ecological competition is the conflict that arises…

The study of the flow of energy within an ecological system from the time the energy enters the living system until it is ultimately degraded to heat and irretrievably lost from the system. It is also referred to as production ecology, because…

The methods required for the measurement of features of plant and animal populations or for quantifying energy flow or other aspects of ecological communities. Ecologists are concerned with such a wide range of variables that they may use many other…

The use of computer simulations or mathematical equations to address questions that cannot be answered solely by experiments or observations. Ecological models have two major aims: to provide general insight into how ecological systems or ecological…

A directional change in an ecological community. Populations of animals and plants are in a dynamic state. Through the continual turnover of individuals, a population may expand or decline depending on the success of its members in survival and…

The study of insects that have a direct influence on humanity. Though this includes beneficial as well as harmful species, most attention is devoted to the latter and how they become pests and are controlled. The emphasis on managing harmful insects…

An obligate association formed between the roots of many plant species, especially trees, and a diverse range of soil fungi. The fungi and the finest, terminal root tips interact to form joint organs called ectomycorrhizas (Fig. 1). In…

A peculiar order of silk-spinning, orthopteroid insects, commonly called the embiids or web spinners, which are related to termites. The order Embioptera (also known as Embiidina or Embiodea) comprises about 300–400 described species, which are…

The sum of all external factors, both biotic (living) and abiotic (nonliving), to which an organism is exposed. All of the outside factors to which an organism is exposed comprise its environment (Fig. 1). The environment has a tremendous influence…

The name given to any of three carnivorous mammals in the genus Mustela (family Mustelidae); also known as the polecat. There are three species of ferrets, also termed polecats, belonging to the genus Mustela in the family Mustelidae of the order…

A group of grasses belonging to the genus Festuca used for both hay and pasture. There are approximately 100 species of fescue, and more than 30 are represented in the United States. Tall fescue (F. arundinacea; alternatively Lolium arundinaceum),…

A method of dating geological and archeological specimens by counting the radiation-damage tracks produced by spontaneous fission of uranium impurities in minerals and glasses. During fission two fragments of the uranium nucleus fly apart with high…

The trees, shrubs, herbs, bacteria, fungi, and animals, together with the surrounding air, soil, water, organic debris, and rocks (environmental substrate), interacting inside a defined boundary. Forests and woodlands occupy about 38% of the Earth's…

Fossil members of the group of primates constituting the apes. Apes and humans are closely related primates in the superfamily Hominoidea. The living hominoids are subdivided into the families Hylobatidae and Hominidae. The hylobatids, or lesser…

Extinct members of the order of mammals to which humans belong. All current classifications divide the living primates (order Primates) into two major groups (suborders) [Fig. 1]: the Strepsirhini (Strepsirrhini) or "lower" primates (lemurs,…

A physiologically interactive system within which growth, adaptation, species composition, nutrient cycling, biological productivity, and energy flows among inland aquatic microbial, plant, and animal communities are integrated with the environment.…

A large and diverse order of conspicuous brown algae (class Phaeophyceae), including such well-known seaweeds as Fucus and Sargassum. Definitive features of members of the Fucales include apical growth, production of sex organs in cavities, and a…

The subdiscipline in mycology and ecology that examines community composition and structure; responses, activities, and interactions of single species; and the functions of fungi in ecosystems. The fungi, as they have been historically classified,…

A group within the cnidarian subclass Octocorallia (class Anthozoa), comprising organisms known as gorgonians. Common names for members of the Gorgonacea (Figs. 1–5) include sea rods (Fig. 4a), sea fans (Fig. 4b), sea feathers (Fig. 4c), bamboo…

A biological community that contains few trees or shrubs, is characterized by mixed herbaceous (nonwoody) vegetation cover, and is dominated by grasses or grasslike plants. Grasslands are areas of herbaceous terrestrial vegetation dominated by…

A desert plant, Parthenium argentatum, cultivated as a source of rubber. Guayule belongs to the aster family (Asteraceae). It is a native perennial shrub that grows in the Chihuahuan Desert of north-central Mexico and southwestern Texas. The plant…

A group of species that utilize the same kinds of resources, such as food, nesting sites, or places to live, in a similar manner. Emphasis is on ecologically associated groups that are most likely to compete because of similarity in ecological…

The requirement of high salt (NaCl) concentrations for growth of microorganisms. Microorganisms (mainly bacteria) can be classified by their physiological tolerance to salt (Fig. 1). Most normal bacteria, such as Escherichia coli, and most…

The consumption of living plant tissue by animals. Plants and the animals that consume them constitute roughly one-half of the scientifically described species. Herbivorous species occur in most of the major taxonomic groups of animals, including…

The largest subclass in the class Bivalvia, phylum Mollusca. The subclass Heterodonta contains some of the most ecologically important bivalves (Fig. 1). For example, marine clams, cockles, and shipworms are heterodonts. Formerly, the class Bivalvia…

A species of fossil human from the Pleistocene representing a specialized side branch in human evolution in Africa and Eurasia. Homo erectus (Fig. 1) was a common, widespread, and long-surviving ancestor of modern humans (H. sapiens). Fossil remains…

The diversity of biological and genetic differences observed in the human population. Anthropologists study human biology to better understand the extent of human biological variability, to explain the mechanisms that create and pattern this…

The branch of ecology that considers the relations of individual persons and human communities with their particular environment. Human ecology is concerned with learning how the distributions and numbers of humans are determined by interactions…

The study of the establishment, spread, and ecological impact of species translocated from one region or continent to another outside their normal range, particularly when the translocation is the result of human activity (intentional or otherwise).…