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mass extinction
(Encyclopedia)mass extinction, the extinction of a large percentage of the earth's species, opening ecological niches for other species to fill. There have been at least ten such events. The five greatest were thos...ecology
(Encyclopedia)ecology, study of the relationships of organisms to their physical environment and to one another. The study of an individual organism or a single species is termed autecology; the study of groups of ...Echinodermata
(Encyclopedia) CE5 Internal anatomy of a sea star, representative of the phylum Echinodermata Echinodermata əkīˌnōdûrˈmətə [key] [Gr.,=spiny skin], phylum of exclusively marine bottom-dwelling invertebra...salmon, in zoology
(Encyclopedia)salmon sămˈən [key], member of the Salmonidae, a family of marine fish that spawn in freshwater, including the salmons, the trouts, and the chars (subfamily Salmoninae), the whitefish and the cisco...forest
(Encyclopedia)forest, a dense growth of trees, together with other plants, covering a large area of land. The science concerned with the study, preservation, and management of forests is forestry. A forest is an ec...turtle
(Encyclopedia)turtle, a reptile of the order Chelonia, with strong, beaked, toothless jaws and, usually, an armorlike shell. The shell normally consists of bony plates overlaid with horny shields. The upper portion...atmosphere
(Encyclopedia) CE5 Atmosphere atmosphere [Gr.,=sphere of air], the mixture of gases surrounding a celestial body with sufficient gravity to maintain it. Although some details about the atmospheres of other plane...deafness
(Encyclopedia)deafness, partial or total lack of hearing. It may be present at birth (congenital) or may be acquired at any age thereafter. A person who cannot detect sound at an amplitude of 20 decibels in a frequ...protein
(Encyclopedia)protein, any of the group of highly complex organic compounds found in all living cells and comprising the most abundant class of all biological molecules. Protein comprises approximately 50% of cellu...carbon
(Encyclopedia) CE5 The three solid forms of pure carbon: In the diamond crystal each carbon atom is surrounded symmetrically by four other carbons (at each of the four corners of a tetrahedron). In the graphite c...Browse by Subject
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