Emerald Robinson: Hi! I am Emerald Robinson and in this What Is Video we are going to discuss a group of organisms called protist. Protists are organisms that have a nucleus and other membrane-bound organelles. Most are one-celled and they are classified as plant, animal, or fungus like; meaning they have things in common with these organisms, but they are not quite the same thing. This is because they are relatively simple and don't have tissues and organs. If you think this definition sounds a little confusing, that's with good reason. Biologists use the protist group as sort of a garbage can. If a form of life doesn't meet the criteria for being a plant, animal, or fungus and it has a nucleus, it's classified as a protist. Still there is a few characteristics than those protists share. Because protists have a defined nucleus, they belong to the domain Eukarya and are called eukaryotes. Protists were probably the first eukaryotes according to what's called Endosymbiotic Theory. The first protist formed when cells that did not have a nucleus engulfed smaller cells.
Over many years these smaller cells evolved into the larger cells, nucleus, and other organelles. Most protists live in water or very wet environments and most are able to move. Some swim via whiplike projections called flagella. Some glide using hair-like extensions called cilia, and some pull themselves along using pseudopods, false feet made of cytoplasm. Some protists are free-living and some are parasites; some make their own food and some get nutrition by hunting food or by simply absorbing it from their environment.
Protists can reproduce via sperm and egg or by binary fission, splitting into two genetically identical cells. Protists may be simple forms of life, but they are certainly one of the most diverse.