biology-dictionary_11-06-2009

Recombination The formation of new gene combinations; in eukaryotes, may be accomplished by new associations of chromosomes prod ...

Releaser A signal stimulus that functions as a communication signal between individuals of the same species. Releasing hormone A ...

Reptile Any of various cold-blooded, usually egg-laying vertebrates of the class Reptilia, such as a snake, lizard, crocodile, t ...

Reticular formation A brain circuit involved with alertness and direction of attention to selected events; consists of a loose n ...

Ribosomal RNA (rRNA) The most abundant type of RNA. Together with proteins, it forms the structure of ribosomes that coordinate ...

Rotifers A class of the phylum Aschelminthes distinguished by the corona, a retractile trochal disk provided with several groups ...

SA (sinoatrial) node The pacemaker of the heart, located in the wall of the right atrium. At the base of the wall separating the ...

Schwann cells A chain of supporting cells enclosing the axons of many neurons and forming an insulating layer called the myelin ...

Seconday meristem In flowering plants, meristems develop from cells that suspend their ability to divide, and resume this activi ...

Secondary succession A type of succession that occurs where an existing community has been severely cleared by some disturbance. ...

Selection coefficient The difference between two fitness values, representing a relative measure of selection against an inferio ...

Sensory neuron A nerve cell that receives information from the internal and external environments and transmits the signals to t ...

Sexual selection Selection based on variation in secondary sex characteristics, leading to the enhancement of sexual dimorphism. ...

iphoning A pipe or tube fashioned or deployed in an inverted U shape and filled until atmospheric pressure is sufficient to forc ...

Social dominance A hierarchical pattern of social organization involving domination of some members of a group by other members ...

Somatic nervous system The branch of the motor division of the vertebrate peripheral nervous system composed of motor neurons th ...

Species-specific Characteristic of a particular species. Specific Unique; for example, the proteins in a given organism, the enz ...

Sphingosine A basic, long chain, unsaturated amino alcohol, C 18 H 37 NO 2 , found combined with lipids in the brain and in tiss ...

Spliceosome A complex assembly that interacts with the ends of an RNA intron in splicing RNA; releases an intron and joins two a ...

Sporopollenin A secondary product, a polymer synthesized by a side branch of a major metabolic pathway of plants that is resista ...