incubation -- n. In birds and reptiles, the maintaining of a constant temperature during the development of the embryo. Birds incubate their eggs by sitting on them (also called brooding),while other animals, like crocodiles, bury their eggs in organic matter. If eggs are not incubated, the embryos within those eggs generally die. Some dinosaurs may have incubated their eggs by burial in sediment, in organic matter, or by brooding like birds.
ingestion -- The intake of water or food particles by "swallowing" them, taking them into the body cavity or into a vacuole. Contrast with absorption.
integrin -- adhesive protein of the extracellular matrix in animals.
island arc -- n. A curved chain of islands that rise from the sea floor, usually near a continent. The convex side usually faces the open ocean, while the concave side usually faces the continent, e.g., the Aleutian Islands in Alaska; volcanic arc- syn.
isotopic analysis -- n. The study of the geochemistry of stable isotopes in naturally occurring sediments and biological structures. Stable isotopes are atomic variations of elements that are stable over long periods of time, meaning they do not radioactively decay. Several elements, like oxygen and carbon, have several stable forms. Oxygen, for example, occurs in nature as 16O and 18O ó these two forms are isotopes. They have different numbers of neutrons (16O has two more neutrons than 18O), and and is therefore heavier. Because the two isotopes have different masses, chemical and physical reactions like bonding, evaporation, and precipitation occur at different frequencies. The ratio of stable isotopes is preserved in chemical compounds like water, ice, and calcium carbonate and provides information on the environmental conditions at the time the compound formed. For example, the ratio of 18O/16O in an ice sample is linked to the water temperature of ancient oceans, which in turn reflects ancient climates.