Karyotype: A picture of all the chromosome pairs in a nucleus lined up by size. This picture is used to determine the sex of the organism and to determine if the organism has the correct number of chromosomes for its species.
Keratin: A protective protein found in skin cells.
Kidney: An organ that removes (filters) waste from the blood. Humans have two kidneys located on the right and left side of the lower back.
Kingdom: A taxonomic ranking group composed of similar phyla. There are six kingdoms of life: Animalia, Plantae, Fungi, Protista, Archaebacteria, and Eubacteria.