Diploid Normal amount of DNA in somatic cells, in the form of paired (homologous) chromosomes, in contrast to germline cells (sperm and eggs) which have a single set of chromosomes, and are haploid.
Endosymbiosis The mutually advantageous relationship of previously free-living precursors of mitochondria and chloroplasts with the larger cells they came to live in early in the evolution of eukaryotic cells.
Epithelium Cells that line surfaces in the body. One of the four basic types of tissue that make up the body, along with nervous tissue, muscle tissue, and connective tissue.