Cell structure of a multicellular animal.

Multicellular animals are characterized by the fact that they consist of various cells that have different origins, structures and, accordingly, functions. Some animal cells lack nuclei. For example, the red blood cells of humans and other mammals lack nuclei. Amphibians have nuclei in erythrocytes. Also, animal cells are characterized by the absence of various plastids. These organelles are characteristic of plants and only some representatives of protozoa and bacteria. Animals that have chloroplasts include sea slugs and some aphids.