Glossary

Glossary: I

IUCN categories

International Union for Conservation of Nature (IUCN) maintains a Redlist of species that are threatened internationally. For more information, see: http://www.redlist.org/. We have modified some of the IUCN categories for simplicilumped some of their categories together for simplicity: critically endangered and endangered together are considered "endangered." We consider vulnerable and least concern/conservation dependent and least concern/near threatened to be "threatened."

ice cap

a large body of land ice that forms when large snowfalls and low temperatures encourage the transformation of snow into ice, often persisting throughout many years. Ice caps are typically less than 50,000 km2 in area but are large enough to submerge the underlying topography.

ichthyology

ichthyologist

The study of fishes, which includes bony fishes (Osteichthyes), cartilaginous fishes (Chondrichthyes) and jawless fishes (Agnatha). It is a branch of zoology and, with the extraordinary geographic and taxonomic diversity of fishes, covers a broad range of disciplines.

imbricate

with parts that overlap each other, such as scales.

indeterminate growth

Animals with indeterminate growth continue to grow throughout their lives.

indigenous

Native to a particular country or area.

indirect development

development from egg to adult form occurs through intermediate phases in which the animals are very different, morphologically, ecologically, and etc. from the adult. Any development which involves a larval stage, as in insects and many amphibians, is a form of indirect development.

infrared/heat

(as keyword in perception channel section) This animal has a special ability to detect heat from other organisms in its environment.

insectivore

An animal that eats mainly insects or spiders.

interambulacral

those areas of an echinoderms body that lie between the ambulacra (areas with tube feet)

internal fertilization

fertilization takes place within the female's body

interstitial

referring to the space between cells, atoms or molecules, or soil particles. Interstitial cells are those cells that exist in the connective tissues between other tissues and structures. This term is most often used to refer to the insterstitial cells of the testes that lie between the seminiferous tubules.

intertidal or littoral

the area of shoreline influenced mainly by the tides, between the highest and lowest reaches of the tide. An aquatic habitat.

introduced

referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.

introduced range

any areas in which an animal now occurs outside of its native range.

invertebrate

An animal which lacks a backbone (such as insects, spiders and crustaceans).

island endemic

animals that live only on an island or set of islands.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).