Paramecia is a form of protist.
Organisms can be divided into prokaryotes – unicellular primitive life forms without a cell nucleus – and eukaryotes – which have a cell nucleus and include animals and plants. Protists belong to eukaryotes, but they form an extremely diverse group that includes everything except animals, plants, and fungi. Some are unicellular, while others are multicellular, but they are distinguished from non-protists by not having organs or different types of tissue. While they appear to provide no direct proven benefits to humans, they play a crucial ecological role, and without them more advanced life forms could not have evolved. They also have several important uses.
Most protists are microscopic, but some are only visible to the naked eye and others can form large colonies and structures. They include protozoa – mobile single-celled organisms – and various types of algae, such as diatoms – tiny photosynthetic life forms with silica shells – and marine algae that can grow up to 30.5 meters in length. While some protozoa are responsible for serious human illness, most are harmless and protists in general are crucial to the world’s ecosystems.
Algae, which are made from protists, play an important role in maintaining the planet’s oxygen levels.
Algae and diatoms use photosynthesis to make food, absorbing carbon dioxide from the atmosphere and releasing oxygen. These protists are extremely numerous in the oceans and fresh water and therefore play an important role in maintaining the planet’s oxygen levels and storing carbon. In fact, algae produce about half of the oxygen generated by photosynthesis on the planet. Along with other protists, they form a large part of the marine plankton which is the lowest level of the ocean food chain and thus a crucial part of marine ecology. On land, soil protozoa help plants grow by consuming bacteria and releasing their nutrients in a form that can be easily absorbed by the roots.
Polluted water treatment
Certain protists such as seaweed can be used as a food source in dishes like sushi and are very rich in nutrients like iodine.
Sewage and other forms of sewage can pose a serious threat to human health and cause great damage to ecosystems if they can simply run into rivers or be dumped into the ocean. Hence, it is sent to treatment plants to remove harmful bacteria, unpleasant odors and suspended organic matter. Protozoa play an important role in this process, preying on bacteria and consuming large amounts of organic matter, helping to clarify the water and make it safe for disposal.
Protists as a food source
Protists help control bacterial populations in the human gut.
Many types of seaweed are edible and are an important food source in some coastal regions. Seaweeds are cultivated in some countries, such as Indonesia and the Philippines, both for food and because of the useful substances that can be extracted from them. Some of them are used as food additives, for example as gelling agents and to improve water retention. Seaweed is also a good source of the essential element iodine.
Sewage travels through sewer lines to a treatment facility, where it is usually broken down by anaerobic means.
It may be that protozoa help control bacterial populations in the human gut. There is a wide variety of bacteria normally present in the human intestine and most of the time they are either beneficial, helping to break down food, or harmless. However, it is believed that the protozoa that feed on these organisms can help keep their numbers under control and prevent imbalances between the different types.
Scientific Research and Other Uses
Algae for biofuels can be grown on land unsuitable for most other uses.
Protists have been the subject of a great deal of research, not only to improve knowledge of the organisms themselves, but also to help understand more general biological processes. Slime molds, for example, are large colonies of amoeba-like organisms that creep in unison over soil, tree bark, and other damp surfaces, consuming various microorganisms as they go along. They are unusual in that instead of consisting of clearly defined cells, they simply have large numbers of nuclei floating within cellular fluid, rather like one huge cell with many nuclei. At a certain point, this mobile, animal-like, phase comes to an end and the slime mold ceases moving to form structures that release spores. Biologists study slime molds to learn more about the ways cells behave and differentiate.
The protists are a group of life forms that are neither plant nor animal.
The remains of diatoms are also useful to scientists. When these organisms die, their tiny silica shells fall to the ocean or lake floor, forming sediments known as diatomaceous earth. Different species, which can be identified by their shells, have different preferences regarding water temperature, and so, by studying ancient samples of diatomaceous earth, scientists can learn a lot about past climates.
There are a number of other practical uses for diatomaceous earth. It is porous, but the spaces between the particles of which it is made up are very small, making it useful for filtering water, and other liquids. It is used in many filtration systems, and has the advantage of being chemically very inert, and so can be used to filter liquids that would react with filter paper. Since diatom shell fragments are hard and often sharp-edged, diatomaceous earth can be used as an abrasive in cleaning powders and pastes. It is also added to animal feed to rid livestock of intestinal worms; the abrasive effect damages worm tissue, eventually killing them.