Eukaryotes
Eukaryote, organism whose cells contain a nucleus , a saclike structure that encloses the cell’s hereditary materials. The presence of a nucleus distinguishes eukaryotes from prokaryotes , those simple, one-celled organisms in which the hereditary material floats free within the cell. Unlike prokaryotes, eukaryotes display a tremendous diversity of form, from complex, single-celled amoebas, diatoms, and dinoflagellates to multicellular plants , animals, and fungi. Only the eukaryotic cell is capable of a high degree of specialization, and specialization is what makes multicellular organisms possible. Just as banks, post offices, and other specialized workplaces are intrinsic to a city, cells tailored for certain jobs are intrinsic to more-complex organisms. Working in concert, specialized cells can create a higher level of organization known as tissues, such as the growing shoot of a plant or the spiny skin of a sea star. Coordinated tissues form organs and, in animals, these organs c...