When a snake flicks its tongue, it is gathering odor particles for transfer to two fluid-filled sacs at the roof of the mouth -- Jacobson's organs -- that lead to a second, smaller olfactory chamber. The tongue is used only to assist in this process; snakes do not have a sense of taste.
A eukaryote is a type of cell (or unicellular organism) that possesses a nucleus and membrane-bound organelles, in contrast to prokaryotes (bacteria and archaea) which don't. Eukaryote means good/true nut/kernel in Greek, referring to the nucleus, while prokaryote means before nut/kernel.
A eukaryote is an organism with complex cells, or a single cell with a complex structure. In these cells the genetic material is organized into chromosomes in the cell nucleus. Animals, plants, algae and fungi are all eukaryotes. There are also eukaryotes amongst single-celled protists. In contrast, simpler organisms, such as bacteria and archaea, do not have nuclei and other complex cell structures. Such organisms are called prokaryotes. The eukaryotes are often treated as a superkingdom, or domain. Eukaryotes evolved in the Proterozoic eon.