Genetic variation is stored in a populationâs gene poolâthe combined. alleles of all of the individuals in a population. Different combinations of. alleles in a gene pool can be formed when organisms mate and have offspring. Each allele exists at a certain rate, or frequency.
Also found in: Wikipedia. cosÂ·tal surÂ·face. the surface of certain structures that face the ribs; they are the costal surfaces of the lungs (facies costalis pulmonis [TA]) and the scapula (facies costalis scapulae [TA]).
1. pertaining to the ribs or the upper sides of the body: costal nerves. 2. pertaining to, involving, or situated near a costa. [1625â35; < Medieval Latin costÄlis of the ribs = Latin cost(a) rib, side + -Älis -al1] cosâ²talâ¢ly, adv.