kingdom Protista

Protists are a diverse collection of many organisms. Although there are some exceptions, they are mainly microscopic and unicellular , and are made up of a single cell . Protist cells are highly organized with a nucleus and specialized cellular machinery known as organelles . At one time, simple organisms like amoebae and single-celled algae were classified together into a single taxonomic category: the kingdom Protista . However, the emergence of better genetic informationit has led to a clearer understanding of the evolutionary relationships between different groups of protists. Understanding protists and their evolutionary history is always in scientific discussion.

What is the Protista kingdom?

The Protista kingdom is a classification of organisms known as eukaryotes, formed mainly by unicellular and microscopic microorganisms that have a nucleus and organelles and by some multicellular organisms that do not fit into any group.

  • What does it consist of
  • Characteristics of the Protista kingdom
  • Source
  • Evolution
  • Classification
  • Habitat
  • Nutrition
  • Reproduction
  • Breathing
  • Cell types of the Protista kingdom
  • Dominion of the Protista kingdom
  • Profits
  • Importance
  • Examples of organisms from the kingdom Protista

What does it consist of

The Protista kingdom is the kingdom that contains eukaryotic organisms , in other words it includes organisms that cannot be classified within the other three eukaryotic kingdoms : Fungi, Animalia or Plantae.

Characteristics of the Protista kingdom

The main characteristics of the Protista kingdom are the following:

  • Many of these organisms are unicellular and very few are multicellular .
  • They are generally bacteria that can cause various diseases.
  • They are derived from other ancient organisms , and have a simple structure typical of eukaryotic organisms.
  • Its nutrition is autotrophic , heterotrophic or by photosynthesis .
  • They need moisture to survive, and none can live in the air.
  • They can reproduce asexually as well as sexually .
  • They have a respiratory system that works through an aerobic process.
  • They are able to move and move , either by crawling, flagella or cilia.
  • They can become pathogenic due to their characteristics and cause health problems.


Scientists believe that the first protists emerged about 1.4 billion years ago as aerobic organisms that had the ability to photosynthesize . From them arose many groups that gave rise to the heterotrophic protists . The evolution of protists is basically the history of the eukaryotic cell.  Possibly the first protists were amoeboids that captured the particles by means of phagocytosis and had flagella , before or after they acquired mitochondria , and many also had chloroplasts, believed to have originated through an association between primitive phagocytic eukaryotic flagellates and symbiotic prokaryotes .


Protists have many evolutionary lines that are difficult to define. Most are unicellular and microscopic , although some form colonies . This organization almost reaches the higher multicellular organisms indicating evolution from protist ancestors . Protists are located in an intermediate kingdom , and can be found from eukaryotic single-celled organisms and simple colonies, to some higher algae and transition groups .


The Protista kingdom is divided into two large groups that are:

  • Algae : they are organisms that have a single cell or unicellular , and generally live in water , although some can inhabit humid places . Their reproduction is sexual or asexual and among them we have red, green, brown algae.
  • Protozoa : they are also unicellular that have a type of heterotrophic nutrition . They reproduce asexually by bipartition . Some of them are parasites and are classified depending on their locomotion , so that we can find flagellates, ciliates, rhizopods and sporozoans.


The habitat of the kingdom Protista is mainly adapted to existence in the air , so that protists are not directly aquatic , although they can develop in humid terrestrial environments or in the internal environment of other organisms.


Animals that belong to the Protista kingdom are autotrophs , this means that they feed by photosynthesis , although they can also be heterotrophic . Many of them can present both modes of nutrition at the same time. Heterotrophs can be by ingestion or by osmotic absorption . Some of these animals are parasites , which can even cause very serious diseases in humans.


The type of reproduction that occurs in the Protista kingdom can be asexual or sexual , depending on the characteristics of the environment , and can sometimes alternate between the two types of reproduction. When conditions are optimal, it can reproduce asexually and colonize the environment; and when there are strong pressures for the species and adverse conditions, sexual reproduction occurs .


The members of the Protista kingdom do not have any type of respiratory system, so the respiration mechanism is by means of gas diffusion through the plasma membrane . They can be aerobic and anaerobic and the type of respiration that occurs is cellular respiration that takes place through the mitochondria in the protists.

Cell types of the Protista kingdom

The type of cells that we find in the Protista kingdom are prokaryotic cells and the organisms that are included in this kingdom can be unicellular or multicellular .

Dominion of the Protista kingdom

The Protista realm domain belongs to the Eukarya domain which contains four kingdoms. This grouping is based on the fact that this type of organism does not fit into any of the other three kingdoms of eukaryotes.


Some members of the Protista kingdom are beneficial to humans, many convert atmospheric nitrogen into organic nitrogen necessary for plants to grow. Green algae also produce oxygen . Some protozoa are also food for other small animals and some are responsible for secreting mineral substances that form deposits in the seas forming limestone . There are also those that help cattle to digest food.


Protists are the most important part of plankton essential for aquatic ecosystems and for soil-dwelling creatures . The Protista kingdom is the one that represents the origin and evolution of the eukaryotic cell.  Many of them are organisms that help maintain balance between living animals. They are also the first step in the food chain because they are fed by small creatures that later will be the food of other animals, or will become organic compounds that plants feed on.

Examples of organisms from the kingdom Protista

Some examples of protist organisms are the following:

  • Plasmodium falciparum that causes malaria, transmitted by the Anopheles mosquito.
  • Trypanosoma cruzi that causes Chagas disease in Latin America.
  • Plasmodium vivax causing malaria.
  • Plasmodium malariae which also transmits malaria.
  • Leishmania donovani which causes leishmaniasis disease.
  • Cyclospora cayetanensis which causes disease in humans and primates .
  • Babesia canis that infects red blood cells and causes anemia.

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