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]).
costa (plural costas or costae) ( 1 anatomy) A rib. ( 2 biology) A riblike part of a plant or animal, such as a middle rib of a leaf or a thickened vein or the margin of an insect wing. (entomology) The vein forming the leading edge of most insect wings.