Polypeptide
A protein or part of a protein made of a chain of amino acids joined by a peptide bond. 2. A molecule made of two or more amino acids joined by peptide bonds.

Polyphyletic group
A set of species descended from more than one common ancestor. The ultimate common ancestor of all species in the group is not a member of the polyphyletic group.

Population
A group of individuals of the same species that are potentially or actually interbreeding. 2. A group of organisms, usually a group of sexual organisms that interbreed and share a gene pool. 3. A geographically defined group of specific organisms sharing a common gene pool.

Population Genetics
The study of variation in genes among a group of individuals. 2. The study of processes influencing gene frequencies.

Population Risk
The risk of a condition or trait to occur in the general population.