ZOOLOGY STUDY GUIDE - Ye. O. Nevedomska - 2013

LECTURE 2. ZOOLOGY AS A SCIENCE

4. Distribution of Animals in the Biosphere

Animals inhabit all PARTS OF THE biosphere: the hydrosphere, atmosphere, and lithosphere. The World Ocean is populated by animals from its surface to its deepest trenches. For instance, worms, Mollusks, and crustaceans have been found at depths of around 11,000 m.

Aquatic animals (hydrobionts) are divided into several groups:

✵ plankton (from Greek plankton — wandering) is a collection of organisms that inhabit the Water Column and are passively carried by currents; zooplankton includes Protozoa, jellyfish, worms, crustaceans, and invertebrate larvae;

✵ nekton (from Greek nektos — swimming) is a collection of organisms capable of actively swimming in water over significant distances; nektonic organisms include, for example, cephalopods;

✵ benthos (from Greek benthos — depth) is a collection of organisms that lead a bottom-dwelling lifestyle; zoobenthos includes protozoa, Sponges, Coelenterates, worms, mollusks, and crustaceans.

Animals that inhabit the atmosphere — aviabionts — are concentrated mainly in its lower layers near the Earth's surface, though some can ascend to significant heights. Arachnids are found at altitudes of about 9,000 m, and insects (butterflies, hymenopterans) at 600 m.

Animals that inhabit the lithosphere — lithobionts — are unevenly distributed. Most soil dwellers — edaphobionts (from Greek edaphos — soil, earth, bios — life) inhabit the surface layers, rarely going deeper than 50 cm. Earthworms, termites, and leafcutter ants sometimes burrow to depths of 5-6 m in search of moist layers. Among lithobionts inhabiting the Earth's surface, a distinction is made between dendrobionts (from Greek dendron — tree, bios — life), which live on woody vegetation, and chortobionts (from Greek chortos — grass, bios — life), which inhabit grasses.

Each landscape zone is characterized by its own fauna (from Greek Fauna — the goddess of forests, fields, and animals) — a historically established community of animals inhabiting a specific territory.