Protein

A large molecule composed of one or more chains of amino acids in a specific order; the order is determined by the base sequence of nucleotides in the gene that codes for the protein. Proteins are required for the structure, function, and regulation of the body's cells, tissues, and organs; and each protein has unique functions. Examples are hormones, enzymes, and antibodies.

Clinal Selection

Selection that changes gradually along a geographic gradient.

Shelter

A place where an animal can rest and be safe. An animal stores food and raises its young in a shelter.