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]).
Fig 1.0 â Overview of the ribs and costal cartilage. The ribs are a set of twelve bones which form the protective âcageâ of the thorax. They articulate with the vertebral column posteriorly, and terminate anteriorly as cartilage (known as costal cartilage).As part of the bony thorax, the ribs protect the internal thoracic organs.They also have a role in breathing â during chest expansion the ribcage moves to permit lung inflation.hey articulate with the vertebral column posteriorly, and terminate anteriorly as cartilage (known as costal cartilage). As part of the bony thorax, the ribs protect the internal thoracic organs. They also have a role in breathing â during chest expansion the ribcage moves to permit lung inflation.