Kingdom Protista: Definition, Characteristics, Classification, Examples

sinaumedia Literacy – Protists are eukaryotic microorganisms that are not animals, plants, or fungi. Although protists cannot be categorized in groups of animals, plants, or fungi, they have characteristics that are similar to the three groups. Therefore, the classification of protists is divided into 3 types, namely animal-like protists, plant-like protists, and mushroom-like protists. Check out a more complete explanation of the following protistas, Sinaumed’s!


Protista is a kingdom that consists of one cell or many cells and has a nuclear membrane (eukaryotic organisms) and is single-celled. Protists can be grouped into three parts, namely animal-like (protozoa), plant-like (algae) and mushroom-like. Most of the Protists live in water, because they do not have a protective body to protect them from dry weather.

So, Kingdom Protista is a simple kingdom because it is only composed of one cell so that it can be grouped in its own kingdom. But there are also those that are multicellular but are still very simple compared to other organisms.

Indonesia as a mega-biodiversity country has a wealth of microorganisms which until now have not been completely recorded and utilized optimally. The book Knowing Indonesian Microorganism Biodiversity for the Welfare of the Nation, written by Indrawati Gandjar Roosheroe, will discuss various microorganisms including protists.



Protists generally have microscopic and macroscopic sizes: Microscopic organisms are organisms that are about 5 µm – 3 mm in size. besides that there are also those that are macroscopic in size with a length of up to 60 meters or more. The following are other characteristics of Kingdom Protista Sinaumed’s:

  • Generally Unicellular: Kingdom Protista is composed of a single cell or unicellular. But there are also multi cellular or many cells. In research of the kingdom Protista, which have many cells or multicellular will live in groups (form colonies).
  • Eukaryotic Cell Type: Protists have a nucleus membrane so they are called as eukaryotic cells. Cells that have a nuclear membrane, but Protists are the simplest prokaryotic living things but are far more complex in terms of structure, function, behavior and ecology when compared to Archaebacteria and Eubacteria.
  • Free Living or Symbiosis: Kingdom Protista can live freely by benefiting each other. But it can also be parasitic to other organisms. If it is parasitic, it will cause many diseases around it.
  • Habitat Generally in Humid Places: As explained above that these Protists live in water or damp places. Not only in fresh water but also in the sea where there is a lot of salt, protists can also live. Protists that live in the sea mostly act as phytoplankton which are the main contributors in the energy supply of food webs.
  • Aerobic and Anaerobic: Aerobic in nature because it requires oxygen for the respiration process which takes place in the mitochondria. It is anaerobic because it does not require oxygen for respiration by symbiotic with aerobic bacteria.
  • Heterotrophic and heterotrophic because they obtain food by absorbing organic molecules and some are photoautotrophic because they have chloroplasts as a place to capture solar energy.
  • Are Motile: There are some Protists that have locomotion tools such as flagella or whip hairs, cilia or vibrating hairs, and pseudopodia or pseudo feet. Thus Protista can be called motile which moves freely.



Characteristics of Protozoa

Protists that are similar to animals have certain characteristics, including:

  • Protozoa are single-celled animals known as unicellular with a body size of only 10-200 µm.
  • Does not have a cell wall.
  • In general, they are heterotrophs, only a small number are autotrophs.
  • Free-living or as a parasite for other organisms.
  • Reproduction sexually or asexually.
  • In general, have a means of movement.

Classification of Animal-Like Protists (Protozoa)

Protozoa are then classified based on their locomotion into four groups, namely:


The movement of Rhizopoda is carried out using pseudopods (pseudopods). Rhizopods do not have a fixed shape because they always change according to their movements. Besides functioning to move, pseudo feet also function to catch food. After the food is digested, the waste products of digestion will condense and pull over to the end of the body and then leave the body. Because they cannot produce their own food, rhizopods are heterotrophic organisms. Rhizopods reproduce by direct division (binary fission). An example of a member of the rhizopoda phylum is Amoeba.

CILIATA phylum

Phylum Ciliata (Ciliophora or Infusiora): As the name implies, ciliates move using cilia (tibbling hairs). Apart from functioning as a means of locomotion, the cilia found in all parts of the body also function to move food so that it can enter through the mouth. Because they cannot produce their own food, ciliates are heterotrophic organisms. Ciliates usually have two cell nuclei called macronucleus (larger size) and micronucleus (smaller size). Asexual reproduction is done by dividing, and sexual is done by conjugation (attaching bodies to each other and exchanging nuclei). An example of a member of this phylum is paramecium sp.


Phylum Flagellata (Mastigophora): Flagella comes from the Latin word which means whip. Mastifophora comes from the Greek “mastig” which means whip, and “phora” which means movement. Most flagellates have two whips on the back of their body, so that when moving it looks as if they are being pushed from behind. Flagellates can be found in sea, water, freshwater, also in symbiosis with other living things, or live as a host or parasite.

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Sporozoa (Apicomplexa): Sporozoa (Sporo = seeds, zoa = animals) are unicellular organisms that do not have locomotion. These organisms move by contracting all the cells. All Sporozoa live as parasites, and food is absorbed directly from the host. Sporozoan reproduction can take place sexually or asexually. Sexually occurs by the meeting of microgametes and macrogametes in the host’s body. While asexual is done by cell division. Examples of sporozoa are plasmodium vivax, malaria, and ovale which are the causes of malaria in humans.


Fungus-like protists are protists with the following characteristics: are eukaryotic, do not have chlorophyll, can produce spores, are heterotrophic. Fungi-like protists are not part of the kingdom Fungi because their body structure and way of reproduction are different from the Fungi group. Fungus-like protists are classified into three phyla, namely:


Myxomycota are also called plasmodial slime molds. All Myxoycota members are heterotrophs because they cannot carry out photosynthesis so they are unable to produce their own food. Usually, plasmodium slime molds have bright colored pigments, which can be yellow or orange.

Plasmodium can grow up to a centimeter (cm) in diameter, however they are unicellular organisms, their body size is large because this group can have many nuclei. Myxomycota habitat can be found in wet forests, weathered wood, and moist soil. In its life cycle there is a collection of amoeboid cells called plasmodium.

Amoeboid cells are free-living cells produced by slime molds. Plasmodium can eat bacteria, pests, spores and other organic components, the food is then digested by the mechanism of phagocytosis. When food is lacking, these cells will combine to form something like mucus. Then this slime-like mass will seek a new environment that better supports its needs.

The mass movement is carried out by contraction of each of the cells that joined earlier. When the habitat is dry and unable to provide food, the plasmodium will stop growing and developing, and will differentiate into a life cycle stage that functions for sexual reproduction.


Acrasiomycota is a cellular slime mold. Unlike the myxomycota which is a plasmodium slime mold. The basic difference between the two is that Acrasiomycota is a haploid organism (only has one set of chromosomes), only the zygote is diploid (has two sets of chromosomes). Meanwhile, Myxomycota lived a more dominant life as a diploid organism. In addition, Acrasiomycota or cellular slime molds have bodies that function to produce spores during asexual reproduction. Acrasiomycota does not have a flagellated life cycle.


OOMYCOTA (water mushroom): Actually the name for water fungus for Oomycota is not quite right, because it is one of the species of this phylum. “Oomycota” comes from the word “Oo” which means egg and “Mycota” which means mushroom. Most oomycota live as decomposers and play an important role in aquatic habitats. Some of its members also live as parasites. Oomycota reproduction can occur asexually or sexually. Asexually they will form zoospores which, if they fall into a suitable environment, will become new organisms. Meanwhile, sexually with the meeting of male gametes and female gametes.


Algae Characteristics

Algae characteristics include:

  • Are unicellular or multicellular.
  • Body size varies, ranging from microscopic algae with a size of 8 µm to macroscopic algae with a size of 60 µm.
  • The shape of the body is fixed due to the presence of a cell wall.
  • Unicellular algae can live solitary or form colonies.
  • Has several types of chlorophyll (chlorophyll a, chlorophyll b, chlorophyll c, and chlorophyll d) stored in chloroplasts.
  • Have photosynthetic pigments besides chlorophyll (xanthophyll [yellow], phycocyanin [blue], fucoxanthin [brown], phycoerythrin [red], and carotenoids).
  • Have a variety of chloroplast shapes (spiral, disc, mesh, bowl, round, and others).
  • Can live like plankton, neuston, or benthos.
  • Reproduce asexually (by binary fission, fragmentation and vegetative spore formation) or sexually (by conjugation, singami and anisogamy).

Classification of Plant-like Protists (Algae)

Plant-like protists are classified into seven phyla, namely:


Phylum Euglenophyta are unicellular organisms that have flagella (whip hairs), eye-catching spots (called stigmas), and chloroplasts. Some members of the phylum Euglenophyta can live as autotrophs (produce their own food) or heterotrophs (hunt for food). When there is enough light, they will live as autotrophs, whereas when the light is weak, they will live as heterotrophs. Usually found in waters and reproduce by dividing. Euglenophyta is a plant-like protist (capable of photosynthesis) and animal-like (capable of active movement).


Chrysophyta (Golden Algae): Phylum Chrysophyta are organisms whose members have a variety of shapes and structures. Algae are usually golden brown in color. Many habitats in fresh water and moist soil, can also be found in the ocean. The dominant color pigments found in the body of Chrysophyta are carotene and phycoxanthin so that the body is golden-brown. But it can also have chlorophyll which gives it a green color.


Pyrrophyta or Dinoflagellates (Fire Algae), The name of the fire algae arises because of several characteristics of the plant-like protist members of this group, for example they appear to glow at night. Some pyrrophyta numbers will increase rapidly at certain times, for example when the water is warm and rich in nutrients so that it makes the ocean appear red-brown ( red tide ). When a red tide appears, the water conditions will be oxygen-poor, and sometimes it becomes toxic, so that when this phenomenon occurs many other living things die.

Actually the color of fire algae can vary, green, yellow, brown and others, this color depends on the pigment that is more dominant in composing its body. Usually fire algae have chlorophyll a and c pigments, xanthophyll, dinosatin and fikobilin. Dinoglagellate species are usually unicellular organisms but some are multicellular. This flaming algae has two flagellates which can make circular motions so they are often also called dinoflagellates (dino = whirlpool). Algae are generally photoautotrophic organisms, but there are also species that live as parasites.

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Phaeophyta (brown algae) are a group of plant-like protists that have a dominant pigment in the form of carotene, namely fucoxanthin, which gives their bodies a brown color. The name of this algae is in accordance with its characteristics, “phaeophyta” comes from the Greek word “phaeios” which means brown. In addition to fucostatin, brown algae also have chlorophyll a, c, and xanthophyll pigments.

Members of the Phaeophyta which have been recognized by more than 1000 species. Almost all brown algae live on the coast, they are mostly thread-like multicellular organisms. The structure of the phaeophyta is very similar to that of a real plant in that it has roots, stems and leaves. Reproduction asexually by dividing to produce zoospores or by fragmentation. Meanwhile, sexually by producing male and female gametes.


Bacillariophyta (Diatoms) This phylum is the phylum that has the most members compared to other groups in plant-like protists. Its known species number about 10,000. In general, Bacillariophyta are unicellular organisms that do not move and live as plankton. Diatoms can be thread-like, round, or triangular in shape. Diatoms have a very distinctive body structure, namely the body consists of a box (hipotheka) and a lid (epitheka), between the box and the lid there is a gap called a rafe. The cell walls contain pectin and silicates, when these organisms die, the shells form soil. Diatoms have a hefty selling price because they can be used for various things.


Rhodophyta (Red Algae) is a phylum that has the dominant phycobilin pigment, namely phycoeitrin, which gives a red color to its body, but Rhodophyta also has phycocyanin pigment, which gives a blue color (not dominant). The known members of this phylum range from about 4000 species, most of which are multicellular organisms. Most rhodophyta live in the sea, and a few can be found in fresh water. Reproduction can take place asexually and sexually. Rhodophyta asexually by forming tetraspores. While sexually directly with male and female gametes.


Chlorophyta (Green Algae) As the name implies, Chlorophyta has a greenish body. The dominant pigment that makes up their body is chlorophyll, besides that they also have a little carotene (yellow pigment). In the body of green algae, chlorophyll gathers in a place called chloroplast. The shape of the chloroplast in each member varies, some are round, spiral, like a star, and others.

Chlorophyta are unicellular organisms that can colonize to form simple multiseller organisms. They are often found living in watery habitats. Because it has chlorophyll, green algae are autotrophic living things that produce food through the process of photosynthesis. Reproduction can occur asexually (through binary fission) or sexually (through conjugation).


Most of the zooplankton in aquatic ecosystems are protists with chlorophyll which are useful as food for fish and aquatic arthropods. In addition, here are some benefits that fall into the Protista category:

  • Entamoeba coli in the large intestine of mammals plays a role in the process of decomposing food scraps.
  • Foraminifera has an exoskeleton of limestone and its fossils in a certain amount can form globigerina soil deposits which can be used as an indication of the presence of petroleum.
  • Radiolaria have a skeleton of a gritty substance. Radiolarians die and leave their shells to form radiolarian soil which can be used as a scouring agent.
  • Paramaecium can also be used as an indicator organism for water pollution by organic matter.
  • In addition to acting as a producer in aquatic ecosystems, Chlorella can also be used as a basic ingredient for making single cell protein (PST).


In addition to beneficial protists for human life, there are some that are detrimental, including:

  • Entamoeba histolytica lives in the human intestine, causing intestinal tissue damage and diarrhea.
  • Entamoeba hartmani lives in the human intestine, causes dysentery but its effects are no worse than Entamoeba histolytica.
  • Entamoeba gingivalis lives in the human oral cavity, between the teeth or on the neck of the teeth, throat and tonsils. Not pathotenic but can exacerbate gingivitis.
  • Trypanosoma gambiense causes sleeping sickness in humans (sleeping sickness or trypanosomiasis). These protists live in human blood. The intermediate vector is the tse-tse fly of the type Glossina tachionides.
  • Trypanosoma evansi causes surrah disease in cattle, horses and buffaloes. Many outbreaks in the tropics, including Indonesia. The intermediate vector is a fly from the genus Tabanus.
  • Leishmaania donovani causes kala azar disease in humans. Sufferers usually have a prolonged fever, enlarged liver and spleen, and ulcers or sores in the intestines.

Examples of Protist Questions and Answers

1. What is the classification of unicellular plant-like protists often called?
Answer: phytoplankton

2. Mention some characteristics of mushroom-like protists?
Answer: Are eukaryotic, do not have chlorophyll, can produce spores, are heterotrophic

3. What is the kingdom protista?
Answer: Protista is a kingdom consisting of one cell or many cells and has a nuclear membrane (eukaryotic organisms) and is single-celled.

Thus the definition, characteristics, classification, benefits and negative effects of protist microorganisms in everyday life, I hope this information is useful, Sinaumed’s. Have a good study!

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