Glossary: R

radial
  1. Arranged like rays. 2. Radiating from or converging to a common center. 3. Moving or directed along a radius. 4. Near the radius (a bone) of the forearm. 5. Developing symmetrically around a central point.
radial symmetry

a form of body symmetry in which the parts of an animal are arranged concentrically around a central oral/aboral axis and more than one imaginary plane through this axis results in halves that are mirror-images of each other. Examples are cnidarians (Phylum Cnidaria, jellyfish, anemones, and corals).

a kind of body symmetry where the animal is arranged around a central axis, examples are jellyfish and anemones.

radius

In anatomy: a long, slightly curved bone of the forearm of tetrapods. It is one of two bones found in tetrapod forearms and is located alongside the ulna, which is the other forearm bone.

In anatomy: a long, slightly curved bone of the forearm of tetrapods. It is one of two bones found in tetrapod forearms and is located alongside the ulna, which is the other forearm bone. Synapomorphy of the Tetrapoda+Eusthenopteron.

radula

the rasping tongue found in most molluscs (Phylum Mollusca, snails, bivalves, and cephalopods).

Tongue-like structure covered with tiny teeth which is protruded from the mouth, and used to scrape food items back into the pharynx. Synapomorphy of Mollusca.

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Climbing plants are also abundant. There is plenty of moisture and rain, but may be somewhat seasonal.

range

The geographical area over which an animal is distributed.

reef

structure produced by the piled-up skeletons of corals (animals in the Class Anthozoa). Coral reefs are found in warm, shallow oceans with few nutrients in the water. They form the basis for rich communities of other invertebrates, plants, and fish.

structure produced by the calcium carbonate skeletons of coral polyps (Class Anthozoa). Coral reefs are found in warm, shallow oceans with low nutrient availability. They form the basis for rich communities of other invertebrates, plants, fish, and protists. The polyps live only on the reef surface. Because they depend on symbiotic photosynthetic algae, zooxanthellae, they cannot live where light does not penetrate.

regenerate

to replace a lost or damaged organ or part through formation of new tissues.

relict

A persistent remnant of an otherwise extinct flora or fauna.

reproduction

the process of producing offspring.

repugnatorial glands

Glands containing noxious fluids which can be released to discourage predators. Synapomorphy of the Myriapoda, also independently evolved in other invertebrate lineages.

resource defense polygyny

a form of polygyny in which males defend critical resources, thereby gaining access to mating opportunities with females who visit those resources.

restinga

An area containing scrubby vegetation typical of sand marine barrier islands .

rhabdite

rodlike structures of certain turbellarians (Phylum Platyhelminthes, Class Turbellaria). These are found in the cells of the epidermis or underlying parenchyma and are discharged in mucous secretions.

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

river

a large, natural body of running water

rivers and streams

a small to large flow of water that flows toward another stream, river, lake, or ocean.

roe

the eggs or egg mass of fish or crustaceans.

ruminant

An animal with a specialized digestive system which includes chewing the cud.