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]).
The serous pericardium, in turn, is divided into two layers, the parietal pericardium, which is fused to and inseparable from the fibrous pericardium, and the visceral pericardium, which is part of the epicardium. Both of these layers function in lubricating the heart to prevent friction during heart activity.The visceral layer extends to the beginning of the great vessels (the large blood vessels serving the heart) becoming one with the parietal layer of the serous pericardium.oth of these layers function in lubricating the heart to prevent friction during heart activity. The visceral layer extends to the beginning of the great vessels (the large blood vessels serving the heart) becoming one with the parietal layer of the serous pericardium.