Radiometric Dating

Also called radiocarbon dating, the process used to determine the age of an object by measuring its radiocarbon content.

Recessive

An inherited trait only expressed by an organism in its physical appearance when the gene controlling it is in the homozygous condition; the recessive allele of that gene.

Regeneration

In plants and animals, the capacity to replace lost or damaged parts by growing new ones; also, asexual reproduction in which an entire organism may be generated from a part of its parent.

Reproduction

The process by which human beings, animals, and plants create more of their own kind.

Reproductive Isolating Mechanism (RIM)

Biological properties of organisms that prevent one species from breeding with another and, thus, distinguish the various species from each other.

Reverse Mutation

Situation in which a mutant allele mutates back into the original allele.

Ribonucleic Acid (RNA)

A substance similar to DNA that carries out DNA's instructions for making specific proteins.