endangered species A species that is in danger of extinction. See CITES; Endangered Species Act; Red Data Book.
Endangered Species Act A federal act passed in 1973 to protect the United States' endangered and threatened species, endangered species being those in imminent danger of extinction throughout their range, e.g. the black-footed ferret, the blue whale, and the California condor, and threatened species being likely to become endangered in the foreseeable future, e.g. the northern spotted owl. Many states also recognize rare species, with low or declining numbers, shrinking habitats, and so on. Endangered species and their habitats are protected by law, and states are required to set up recovery plans.
endemic Describing a population or species that is restricted geographically. Some endemics have evolved in geographical isolation on islands or mountaintops; others may be relics of once widespread species that have become restricted owing to climate change, geological change, or human activity.
endobiont (endosymbiont) A symbiotic organism that lives within the body of its host. See also endosymbiont theory.
endocrine disrupter See endocrine tox-icity.
endocrine toxicity Toxicity that affects the endocrine systems of animals - their hormones - often by blocking receptors for certain hormones. Such endocrine-disrupting chemicals are thought to be involved in fertility problems in humans as well as other animals, and especially in fish and other aquatic organisms. They are also implicated in some cancers, such as breast and testicular cancer. Natural estrogens and synthetic estrogens used in hormone treatments and contraceptives are found in sewage effluent. Other endocrine disrupters include tributyl tin oxide, which causes female dog whelks to become masculinized, and certain industrial detergents, which cause male trout to produce vitel-logenin, an egg yolk protein normally produced only by females.
end-of-the-pipe Pollution or waste treatment processes or devices located immediately at the outlet of a collecting system, e.g. at a sewage outfall. The pollutants are treated before they are discharged to the environment.
endogenous rhythm Cyclical, physical, and biochemical processes that occur in an organism in response to internal stimuli, e.g. the opening and closing of stomata, which usually coincides with dawn and dusk respectively, but which continues even if kept in continuous darkness. See circadian rhythm.
endomycorrhiza See mycorrhiza.
endoparasite See parasitism.
endoparasitoid See parasitoid.
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