How is kingdom protista helpful

A few protist species live on dead organisms or their wastes, and contribute to their decay. The cells of protists are among the most elaborate of all cells. Most protists are microscopic and unicellular, but some true multicellular forms exist.

A few protists live as colonies that behave in some ways as a group of free-living cells and in other ways as a multicellular organism. Still other protists are composed of enormous, multinucleate, single cells that look like amorphous blobs of slime or, in other cases, like ferns. In fact, many protist cells are multinucleated; in some species, the nuclei are different sizes and have distinct roles in protist cell function.

Single protist cells range in size from less than a micrometer to the 3-meter lengths of the multinucleate cells of the seaweed Caulerpa. Protist cells may be enveloped by animal-like cell membranes or plant-like cell walls. Others are encased in glassy silica-based shells or wound with pellicles of interlocking protein strips. The pellicle functions like a flexible coat of armor, preventing the protist from being torn or pierced without compromising its range of motion.

The majority of protists are motile, but different types of protists have evolved varied modes of movement. Some protists have one or more flagella, which they rotate or whip. Others are covered in rows or tufts of tiny cilia that they beat in coordination to swim. Still others send out lobe-like pseudopodia from anywhere on the cell, anchor the pseudopodium to a substrate, and pull the rest of the cell toward the anchor point.

Some protists can move toward light by coupling their locomotion strategy with a light-sensing organ. Protists exhibit many forms of nutrition and may be aerobic or anaerobic. Photosynthetic protists photoautotrophs are characterized by the presence of chloroplasts. Other protists are heterotrophs and consume organic materials such as other organisms to obtain nutrition. Amoebas and some other heterotrophic protist species ingest particles by a process called phagocytosis, in which the cell membrane engulfs a food particle and brings it inward, pinching off an intracellular membranous sac, or vesicle, called a food vacuole [Figure 2].

This vesicle then fuses with a lysosome, and the food particle is broken down into small molecules that can diffuse into the cytoplasm and be used in cellular metabolism. Undigested remains ultimately are expelled from the cell through exocytosis.

Some heterotrophs absorb nutrients from dead organisms or their organic wastes, and others are able to use photosynthesis or feed on organic matter, depending on conditions. Protists reproduce by a variety of mechanisms. Most are capable some form of asexual reproduction, such as binary fission to produce two daughter cells, or multiple fission to divide simultaneously into many daughter cells. Others produce tiny buds that go on to divide and grow to the size of the parental protist.

Sexual reproduction, involving meiosis and fertilization, is common among protists, and many protist species can switch from asexual to sexual reproduction when necessary. Sexual reproduction is often associated with periods when nutrients are depleted or environmental changes occur.

Sexual reproduction may allow the protist to recombine genes and produce new variations of progeny that may be better suited to surviving in the new environment. However, sexual reproduction is also often associated with cysts that are a protective, resting stage. Eukaryotic organisms are distinguished from prokaryotes in that they have a nucleus that is surrounded by a membrane.

In addition to a nucleus, protists have additional organelles in their cytoplasm. The endoplasmic reticulum and Golgi complexes are important for the synthesis of proteins and exocytosis of cellular molecules. Many protists also have lysosomes , which aid in the digestion of ingested organic material. Certain organelles may be found in some protist cells and not in others. Protists that have characteristics in common with animal cells also have mitochondria , which provide energy for the cell.

Protists that are similar to plant cells have a cell wall and chloroplasts. Chloroplasts make photosynthesis possible in these cells. Protists exhibit different methods of acquiring nutrition. Some are photosynthetic autotrophs, meaning that they are self-feeders and capable of using sunlight to generate carbohydrates for nutrition. Other protists are heterotrophs, which acquire nutrition through feeding on other organisms.

This is accomplished by phagocytosis, the process in which particles are engulfed and digested internally. Still, other protists acquire nutrition predominately by absorbing nutrients from their environment. Some protists may exhibit both photosynthetic and heterotrophic forms of nutrient acquisition. While some protists are non-motile, others exhibit locomotion through different methods. Some protists have flagella or cilia. These organelles are protrusions formed from specialized groupings of microtubules that move to propel protists through their moist environment.

Other protists move by using temporary extensions of their cytoplasm known as pseudopodia. These extensions are also valuable in allowing the protist to capture other organisms that they feed on. The most common method of reproduction displayed in protists is asexual reproduction. Sexual reproduction is possible, but typically only occurs during times of stress.

Some protists reproduce asexually by binary fission or multiple fission. Others reproduce asexually by budding or through spore formation. In sexual reproduction, gametes are produced by meiosis and unite at fertilization to produce new individuals.

Other protists, such as algae , exhibit a type of alternation of generations in which they alternate between haploid and diploid stages in their life cycles. Protists can be grouped according to similarities in a number of different categories including nutrition acquisition, mobility, and reproduction.

Examples of protists include algae, amoebas, euglena, plasmodium, and slime molds. Protists that are capable of photosynthesis include various types of algae, diatoms, dinoflagellates, and euglena. These organisms are often unicellular but can form colonies. They also contain chlorophyll , a pigment which absorbs light energy for photosynthesis.

However, the emergence of better genetic information has since led to a clearer understanding of evolutionary relationships among different groups of protists, and this classification system was rendered defunct.

Understanding protists and their evolutionary history continues to be a matter of scientific discovery and discussion. All living organisms can be broadly divided into two groups — prokaryotes and eukaryotes — which are distinguished by the relative complexity of their cells.

In contrast to prokaryotic cells, eukaryotic cells are highly organized. Bacteria and archaea are prokaryotes, while all other living organisms — protists, plants, animals and fungi — are eukaryotes. Many diverse organisms including algae, amoebas, ciliates such as paramecium fit the general moniker of protist. The vast majority of protists are unicellular or form colonies consisting of one or a couple of distinct kinds of cells, according to Simpson.

He further explained that there are examples of multicellular protists among brown algae and certain red algae. Like all eukaryotic cells, those of protists have a characteristic central compartment called the nucleus, which houses their genetic material. They also have specialized cellular machinery called organelles that execute defined functions within the cell.

Photosynthetic protists such as the various types of algae contain plastids. These organelles serve as the site of photosynthesis the process of harvesting sunlight to produce nutrients in the form of carbohydrates. The plastids of some protists are similar to those of plants. According to Simpson, others protists have plastids that differ in the color, the repertoire of photosynthetic pigments and even the number of membranes that enclose the organelle, as in the case of diatoms and dinoflagellates , which constitute phytoplankton in the ocean.

Most protists have mitochondria , the organelle which generates energy for cells to use. The exceptions are some protists that live in anoxic conditions, or environments lacking in oxygen, according to an online resource published by University of California, Los Angeles. They use an organelle called the hydrogenosome which is a greatly modified version of mitochondria for some of their energy production.

For example, the sexually transmitted parasite Trichomonas vaginalis , which infects the human vagina and causes trichomoniasis , contains hydrogenosomes. Protists gain nutrition in a number of ways. According to Simpson, protists can be photosynthetic or heterotrophs organisms that seek outside sources of food in the form of organic material. Protists, such as aphanizomenon flos-aquae and spirulina, are types of blue-green algae that also produce oxygen as a by-product of their respiration cycle.

If not for these little cyanobacteria, Earth would not be the oxygen rich planet it is today. Algae, such as seaweed, also serve as mini-ecosystems for other marine life, especially the juvenile and larval forms that need to hide for safety. Blue-green and brown algae is currently being grown for biofuel, which could eventually replace traditional fossil fuels. Living algae is 50 percent oil, and can be harvested and processed into usable oil, diesel and gas fuel. Plus, the algae grows very fast, allowing producers to keep up with an ever increasing demand.

Modern fossil fuels also originated from the remains of prehistoric animals and brown algae. Other types of protists offer more direct benefits for animals in the form of symbiotic relationships.

Trichonymphs live in the intestines of termites, feeding on the wood cellulose that termites eat and breaking it down into digestible components.