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What are Protists?

Last Updated : 17 Aug, 2022
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Based on their body’s form and function, all living organisms are recognized and categorized. Several traits are likely to make more substantial physical modifications than those of others. Time has a function in additionally this, thus, once a particular body type comes into being, it will influence the outcomes of all additional ensuing design modifications, just because it’s already there. In addition, words, traits that emerged from most likely, previous life were simpler, than the traits that have emerged in subsequent existence. This indicates that life is classified in this way. Forms and their evolution will be tightly intertwined. The variety of life forms is referred to as biodiversity. It is a term that is frequently used to describe the variety of living forms discovered. In a specific area, various living forms share a common habitat and are influenced also by one another. The result is a steady population of various species arrives at being. People have played a role in recent history. In adjusting such balance, communities. Obviously, the variety of these communities is impacted by Specific creatures on land, climate, water, and so forth. Rough There are, according to estimates, roughly 10. There are a billion species in the world, but  We actually only are aware of one or two of several millions of them.




Simple eukaryotic organisms known as protozoa are not classified as either plants, animals, or fungi. Although they are often unicellular, protozoa would be arranged in a Colony. The majority of protists are parasites or live in wet terrestrial habitats.

The word “Protista” comes from the Greek prefix “protestors,” which means “the first.” The cells of these creatures, which are typically unicellular, have a nucleus that is connected to the organelles. Some of them even have locomotion-supporting features like flagella. In light of the fact that plants, animals, and fungi all evolved from a similar protist-like progenitor billions of years ago, scientists suggest that protists serve as a connecting link between these three kingdoms. Despite being a hypothetical organism, this “protists-like” ancestor may have shared certain genes with current animals and plants.

As a result, these organisms are typically regarded as the earliest eukaryotic living forms and the ancestors of fungi, plants, and animals.


Eukaryotic organisms are the main characteristic of all protists. This indicates that their nucleus is membrane-enclosed. The following are some other characteristics of Kingdom Protista:

  • These are mostly aquatic and can be found in soil or even other moist regions.
  • Some of them would be multicellular species, like kelp, however, the majority of them would be unicellular animals. Certain kelp species can reach heights of more than 100 feet. (Huge Kelp)
  • These species’ cells feature a nucleus and organelles, which would be membrane-bound, just like every other eukaryote.
  • Both autotrophic and heterotrophic organisms can exist in them. An autotrophic organism may produce nourishment for itself and endure. Contrarily, a heterotrophic organism must obtain its nutrition from other living things like animals or plants for a living.
  • The individuals in this class exhibit symbiosis. For instance, the multicellular protist kelp (seaweed) offers otters safety from predators within its dense kelp. The otters then consume sea urchins, which typically consume kelp.
  • Protists have been found to exhibit parasitism. Sleeping sickness in humans can be brought on by species like the protozoan Trypanosoma.
  • Protists move around by using their flagella and cilia. Several Protista kingdom organisms have pseudopodia that aid in movement.
  • Asexual reproduction is used by protozoa. Sexual reproduction is extremely uncommon and only happens under stressful conditions.



Protozoans are organisms with only one cell. Since they are heterotrophic and exhibit animal-like behaviors, protozoans have historically been referred to as “animal” protists.

Protozoans that live as parasites inside the bigger organisms are also present. The majority of the members lack a fixed form. A paramecium, on the other hand, has a defined slipper-like shape, while an amoeba can vary its shape forever. The protozoan is an amoeba, and euglena is the best recognized types. Euglena would have chlorophyll, which, makes it different from other members of this group in that it can produce its own sustenance.

Four main categories can be used to categorize protozoans:

  • Protozoans called amoebic are typically found in freshwater or saltwater bodies of water. They can modify their morphology and capture and devour food thanks to their pseudopodia, or artificial feet. Like an amoeba.
  • Protozoans with flagella—As the name suggests, these organisms have flagella. Both parasitic and free-living species are possible. Consider Euglena.
  • They contain cilia all throughout their bodies, which aid in both nourishment and movement, making them ciliated protozoans. They’re always in the water. Consider Paramecium.
  • These organisms are called sporozoans because a stage of their life cycle resembles a spore. Consider Plasmodium, a parasite that causes malaria.

Slime Mould

They are saprophytic creatures, slime molds, they would eat the decayed things. These are very small organisms with several nuclei. Slime molds are typically characterized by the presence of plasmodium aggregates, which are so much readily detectable.


These belong to a different class within the Protista kingdom. Typically, these are multicellular or single-celled organisms. These are primarily found in aquatic sources or saltwater lakes and are photosynthetic. They are distinguished by a rigid cell wall.

Chrysophytes include, for instance, diatoms and golden algae. They are distinguished by having a rigid siliceous cell wall. Cell wall deposits build up over time, resulting in the formation of diatomaceous earth. Beings that use photosynthesis.


Dinoflagellates are photosynthetic organisms that may change color depending on the pigment they contain. They exhibit bioluminescence and have been linked to red tide.


The euglenoid connects plants and animals. Despite not having a cell wall, they can photosynthesize. They function as a heterotroph and consume small organisms when there is no sunshine. A pellicle, which is a protein-rich layer, serves as the body’s exterior covering such as Trachelomonas, Euglena, etc.

Economic Importance

  • The base of the food web is made up of protozoa, which also make the soil fertile.
  • Symbionts, or close relationships between two species from which one benefits, are protists.
  • Some protists can be utilized to make biofuel since they also create oxygen.
  • Many animals eat primarily protists as their main food source.
  • Protists are occasionally captured by humans for use in food production and other industrial processes.
  • One of the few sources of food for whales is phytoplankton.
  • Algae, which are regarded as protists that resemble plants, include seaweed.
  • Several marine animals, including shrimp and crab larvae, eat zooplankton.

Frequently Asked Questions

Question 1: How do protozoa work?


Protists are a diverse group of nucleated single-celled and multicellular creatures. They also have cell organelles, highly specialized pieces of cellular machinery that assist in carrying out numerous life activities. The majority of protists are autonomous autotrophs (like algae), but others are heterotrophic (like amoebas) or even parasitic.

Question 2: Do all protists have one cell?


No, protozoa are not all unicellular. Multicellular protists, or organisms made up of more than one cell, include moulds and algae. The kingdom Protista includes unicellular organisms, including amoeba.

Question 3: How do protozoa make the soil fertile?


They would make or preserve the soil fertility, as they would release the nutrients by bacterial digestion. So protozoa play an essential role in soil fertility.

Question 4:  Why protozoans do not require the transport of oxygen like multicellular organisms?


Because they are so tiny, protozoans can simply diffuse oxygen from the surrounding liquid medium to fuel their metabolism. Protozoans do not need the particular pigments or structures needed by multicellular organisms for the uptake and transportation of oxygen. Therefore, protozoans would create the oxygen.

Question 5: Which would protect euglena?


Euglena would have a protein rich layer, an outer covering called pellicle for the protection.

Question 6: Why does dinoflagellate have red tides?


The waters physically turn red as a result of the crimson plastids on the dinoflagellates. Dinoflagellates profit from unfavorable environmental conditions that cause the extinction of other creatures.