Protists Overview Study Guide

Protists are defined as single-celled organisms belonging to the kingdom "Protista," such as an alga or protozoa. The study of protists is called protistology.


  • Protists are organisms without any highly specialized tissues, are eukaryotic, and belong to the kingdom Protista.
  • They are not plants, animals, or fungii and are normally found in colonies.
  • They include both unicellular and multicellular organisms.
  • They require a medium containing water to survive.
  • Examples include amoeba, seaweed, algae and the organism that causes malaria too.

What term describes the very first protists? The term "protista" means primordial or, ‘first of all’ - the "primitive forms" of all organisms.

Structure-of-Protist-Cell Source

Types of Protists

Based on their similarity to a plant, animal or fungus protists are classified into:

a) animal-like protists called protozoa, which are protists heterotrophic and obtain their nutrition from other organisms.

b) plant-like called protophyta, which are autotrophic protists and synthesize their nutrition by photosynthesis.

c) fungus-like organisms called slime molds and water molds are mixotrophic and form spore-like bodies.

Based on their nutrition, protists can be classified into three broad categories:

1) Autotrophs

  • These protists are generally non-motile and can photosynthesize their food just like plants.
  • They have the pigments required to carry out photosynthesis, and different groups have different pigments which give a characteristic color to their colonies.
  • Autotrophic protists carry out 40% of the world's photosynthesis.
  • Autotrophic protists or protist producers are mostly Algae protists: green algae, brown algae, red algae, dinoflagellates, diatoms, and Euglena.

green-algae Source

2) Heterotrophs

  • These protists are grouped based on the type or lack of locomotive parts.
  • These protists are called "protozoa," which means first animals because they ingest food which is a characteristic of animals.
  • Some protozoans are predators and ingest bacteria, and others ingest dead organic matter, while others are parasites on other living organisms.
  • They include amoeba, paramoecium, sporozoans, slime molds, and water molds.
  • Phagocytosis is one of the few feeding mechanisms in which the protist extends its plasma membrane called "pseudopodia" around the particle to be eaten. Some amoebas use this feeding mechanism.

3) Mixotrophs

  • These protists get their nutrition by heterotrophy when there is prey available and in the absence of food by photosynthesis.
  • The" ideal mixotrophs" use sunlight and prey equally.


The protists reproduce by asexual methods like fission, spore formation or budding, or sexual methods like conjugation, syngamy, meiosis, and fertilization of the gametes.


  • Protists are unicellular eukaryotic organisms
  • Protists can be broadly classified as animal-like protists (heterotrophic protists), plant-like protists (autotrophic protists), and fungus-like (mixotrophic protists).
  • The protists reproduce by asexual methods like fission, spore formation or budding, or sexual methods like conjugation, syngamy, meiosis, and fertilization of the gametes.


1. What are the 5 characteristics of protists?

a) Protists are unicellular with some multicellular organisms too

b) They are eukaryotic and have a nucleus

c) Maybe either autotrophic or heterotrophic

d) They are either parasitic or live freely in the environment

e) Have flagella and cilia for locomotion

2. What is the description of protists?

Protists are eukaryotic organisms with neither plant, animal, or fungus characters. They normally live in water but may be present in any moist soil. They may be autotrophic or heterotrophic and use flagella or cilia for movement.

3. What are the 4 main protists?

The four main protists are flagellates, ciliates, spore-forming protists, and amoeba-like protists.

4. What are the 3 main types of protists?

Animal-like protists, plant-like protists, and fungus-like protists are the three main types of protists.

5. What are the three main methods of movement that different protists have?

Protists use cilia, flagella, or pseudo/axopodia for movement.

6. Are protists Autotrophs or Heterotrophs?

Protists are either autotrophs or heterotrophs.

8. What are protists and give its types?

Protists are a group of eukaryotic organisms that are not plants, animals or fungii. They can be either autotrophs or heterotrophs and are found in loosely connected groups called colonies. Flagellates, ciliates, spore-forming protists, and amoeba-like protists are the types.

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  1. Protists Accessed on 8 Dec 2021.
  2. Protist Accessed on 8 Dec 2021.
  3. Heterotrophic protista Accessed on 8 Dec 2021.
  4. Respiration and nutrition Accessed on 8 Dec 2021.