Marine plankton.

Plankton (from the Greek word planktos, which means "wandering") are communities of mostly microscopic organisms that inhabit watery environments, from oceans to muddy regions. Some plankton drift passively or swim weakly near the surfaces of oceans, ponds, and lakes, while others exist as bottom-dwellers, attaching to rocks or creeping on the ground through sand and silt.

Plankton are classified under the kingdom Protista. During the genesis of protists, a true nucleus, as well as the other components of eukaryotic cells (mitochondria, chloroplasts, endoplasmic reticulum, Golgi bodies, 9 2 flagella and cilia, the functions mitosis and meiosis) arose. Thus these organisms are considered to be ancestral to plants, fungi and animals. While the majority of plankton are unicellular and therefore considered to be simple eukaryotic organisms, at the cellular level they are extremely complex. Plankton should be considered an organism in itself and not be compared to a single...