Plants and Fungi [Protista – Euglenoids, Dinoflagellates, Diatoms and More]


Protista includes organisms that are neither plants nor animals. Protists are eukaryotes which means they have membrane-bounded nuclei and organelles. Some protists are plant-like as they have chloroplast.

These plant-like protists do photosynthesis for the production of their food so are autotrophs. These attributes make them similar to plants but they don’t have proper roots, stems, leaves, or other plant structures. So, they are called algae.

Some organisms which were initially classified into the kingdom Animalia such as euglenoids, and dinoflagellates are now also classified into protists.

There are also some fungi-like protists as they have structures that look like hyphae and are not photosynthetic but also some of them have their initial life phase look like fungi. These include slime molds or water molds. Here is the detailed article:

Plants and Fungi Like Protista

Plant-like protists are called algae. They include single-celled diatoms and multicellular seaweed. Like plants, algae consist of chlorophyll and make food by photosynthesis. Types of algae consist of red and green algae, euglenoids, and dinoflagellates.

They are protists that absorb their food from dead raw material. They are classified into 2 groups, slime molds, and water molds. The majority of fungus-like protists utilize pseudopods, (” false feet”) to move around.

The Algae: Plant-like protists

Algae (singular alga) are photosynthetic protists, performing probably 50 to 60 percent of all the photosynthesis on earth (plants represent most of the rest).

Algae differ from the plants in their sex organs which are unicellular and the zygote is not protected by the parent body. A plant zygote, on the other hand, grows into a multicellular embryo that is protected by adult tissue.

Algae show an amazing variety of growth types. Some are unicellular; others are filamentous. Filaments are made up either of distinct cells or coenocytes (multinucleate structures that lack cross-walls), still others (e.g. seaweeds) are multicellular and intricately branched or set up in leaf-like extensions. A body that is not differentiated into real roots stems and leaves and lacks xylem and; phloem is called a thallus.


In addition to green chlorophyll a, yellow and orange carotenoids, which are photosynthetic pigments found in all algae, other algal phyla have a range of other pigments (such as xanthophylls and phycoerythrin) that are likewise crucial in photosynthesis. Classification into phyla is mostly based on their pigment composition.

Algal life cycles reveal extreme variation, however, all algae other than members of the phylum Rhodophyta (red algae) have formed with flagellated motile cells in at least one stage of their life process.

Almost all algae are aquatic. When actively growing, algae are restricted to moist or damp environments, such as the ocean; freshwater ponds, lakes, and streams; warm springs; polar ice; moist soil, trees, and rocks.

(I) The Euglenoids

Euglenoids have at various times been classified in the plant kingdom (with algae) and in the animal kingdom (in protozoans). Based on molecular information, euglenoids are thought to be carefully related to zooflagellates. They are plant-like in their pigments. Nevertheless, some photosynthetic euglenoids lose their chlorophyll when grown in dark and get their nutrients heterotrophically by ingesting raw material. Other types of euglenoids are constantly colorless and heterotrophic.


Euglenoids have special evolutionary significance as they look like plants and green algae in having comparable pigments and, on the other hand, are also related One of the most uncommon protists to zooflagellates.

(ii) Dinoflagellates

Among the most unusual protist phyla is that of dinoflagellates. Most dinoflagellates are unicellular. Their cells are frequently covered with shells of interlocking cellulose plates impregnated with silicates. Environmentally, dinoflagellates are one of the most essential groups of producers (2nd just to diatoms) in the marine community. Dinoflagellates are known to have occasional population explosions or blooms. These flowers often color the water orange, red or brown and are called red tides.


(iii) Diatoms

The cell wall of each diatom includes 2 shells that overlap where they find it together, just like a petri dish. Silica is deposited in the shell, and this glass-like material is set in elaborate patterns. Diatoms are significant manufacturers in the marine (marine and freshwater) environments because of their very great deals. Diatoms are crucial in the water food cycle.

Further Reading:  Vertebrate Axis Development


 (iv) Brown Algae

Brown algae include the giants of the protist kingdom. All brown algae are multicellular and vary from a couple of centimeters to around 75 meters in length. The biggest brown algae, called the kelps are hard in appearance. They have leaflike blades, stemlike stipes, and rootlike anchoring holdfast. Brown algae prevail in cooler marine waters, particularly along rocky shorelines in the intertidal zone.


(v) Red Algae

The multicellular body type of red algae is commonly made up of complicated interwoven filaments that are fragile and feathery. A couple of red algae are flattened sheets of cells. A lot of multicellular red algae connect to rocks or other substances by a basal holdfast. Some red algae integrate calcium carbonate in their cell walls from the ocean and participate in building coral reefs along with coral animals.



(vi) Green Algae

Green algae have pigments, energy reserve products, and cell walls that are identical to those of plants. Green algae are photosynthetic, with chlorophyll a, chlorophyll b, and carotenoids present in the chloroplasts. Their primary energy reserves are saved as starch. Most green algae have cell walls with cellulose. Because of these and other similarities, it is usually accepted that plants arose from ancestral green algae. Proof from RNA sequencing also shows that green algae and the plants form a monophyletic family tree.

Chlorella is a unicellular non-motile green alga. Its environment is freshwater ponds and ditches. It is easily cultured and has been utilized as a speculative organism in a research study on photosynthesis as well as being investigated as an alternate source of food.


Importance of Algae

Algae have great economic and ecological significance for us. Some algae such as kelps are edible and may be utilized to conquer the shortage of food on the planet. Marine algae are likewise a source of numerous helpful compounds like algin, agar, carrageenan, and bactericides. Algae are major manufacturers of the water community; thus, they play a basic function in food chains, providing food and oxygen to other organisms.

Fungi like Protists

Some protists superficially look like fungi because they are not photosynthetic and some have bodies formed of threadlike structures called hyphae. However, fungus-like protists are not fungi for a number of factors. A lot of these protists have centrioles and produce cellulose as a significant element of their cell walls, whereas fungi do not have centrioles and have cell walls of chitin.

(i) Slime molds or Myxomycota

The feeding stage of a slime mold is a plasmodium, a multinucleate mass of cytoplasm that can grow to 30 cm (1 feet) in size. The plasmodium, which is slimy in look, streams over damp, decaying logs and leaf litter. It frequently forms a network of channels that cover a big surface area. As it creeps along, it consumes bacteria, yeasts, spores, and decaying raw material.

Throughout damaging conditions, slime mold kinds resistant haploid spores by meiosis within stalked structures called sporangia. When conditions become favorable again, spores germinate into biflagellate or amoeboid reproductive or swarm cells that unite to form a diploid zygote. The zygote produces a multinucleate plasmodium, each nucleus being diploid. The plasmodial slime mold Physarum polycephalum is a model organism that has been used to study numerous essential biological processes, such as development and differentiation, cytoplasmic streaming, and the function of the cytoskeleton.




Water molds or Oomycotes

Oomycotes reveal close relations with the fungi and have a comparable structure, however are now regarded as a more ancient group. Their cell walls contain cellulose, not chitin. Their hyphae are aseptate (without cross-walls). Oomycotes consist of a variety of pathogenic organisms, including Phytophthora infestans, which have played infamous roles in human history.

Phytophthora infestans were the cause of the Irish potato famine of the 19th century. It causes a disease commonly called late blight of potatoes. Because of several rainy, cool summer seasons in Ireland in the 1840s, the water mold increased unchecked, triggering potato tubers to rot in the fields. Since potatoes were the staple of Irish peasants’ diet, lots of people (250,000 to more than 1 million) starved to death. The scarcity triggered a mass migration out of Ireland to such countries as the United States.


Multiple Choice Questions (MCQs) – Plants and Fungi

  1. What are Protists?
    • A) Unicellular organisms
    • B) Multicellular organisms
    • C) Neither plants nor animals
    • D) Both A and B
    • Answer: C
  2. What is a characteristic of protists?
    • A) Presence of membrane-bounded nucleus
    • B) Lack of organelles
    • C) Absence of chloroplast
    • D) All of the above
    • Answer: A
  3. Why are some protists called algae?
    • A) They have proper roots, stems, and leaves
    • B) They perform photosynthesis and have chloroplast
    • C) They lack membrane-bounded nucleus
    • D) They are multicellular
    • Answer: B
  4. Which organisms were initially classified into the kingdom Animalia but are now considered protists?
    • A) Diatoms
    • B) Euglenoids
    • C) Dinoflagellates
    • D) Both B and C
    • Answer: D
  5. What is the importance of algae?
    • A) Source of algin and agar
    • B) Major producers in aquatic ecosystems
    • C) Edible, overcoming food shortages
    • D) All of the above
    • Answer: D
  6. Which protist phylum is known for occasional red tides?
    • A) Euglenoids
    • B) Diatoms
    • C) Dinoflagellates
    • D) Brown Algae
    • Answer: C
  7. What is a characteristic of diatoms?
    • A) Unicellular with shells of cellulose plates
    • B) Silica is deposited in their shells
    • C) Important producers in marine environments
    • D) All of the above
    • Answer: D
  8. Which color of light favors the elongation of cells in plants and algae?
    • A) Red light
    • B) Blue light
    • C) Green light
    • D) Yellow light
    • Answer: A
  9. What distinguishes slime molds from fungi?
    • A) Presence of centrioles
    • B) Production of cellulose
    • C) Unicellular structure
    • D) Aseptate hyphae
    • Answer: A
  10. What is the feeding stage of a slime mold called?
  • A) Zygote
  • B) Sporangium
  • C) Plasmodium
  • D) Mycelium
  • Answer: C
  1. Which water mold caused the Irish potato famine?
  • A) Phytophthora infestans
  • B) Plasmodium falciparum
  • C) Myxomycota
  • D) Oomycotes
  • Answer: A
  1. What is the primary energy reserve in green algae?
  • A) Starch
  • B) Glycogen
  • C) Cellulose
  • D) Xanthophyll
  • Answer: A
  1. What is the function of the holdfast in brown algae?
  • A) Photosynthesis
  • B) Anchoring to rocks
  • C) Reproduction
  • D) Nutrient absorption
  • Answer: B
  1. Which phylum of algae is characterized by a multicellular body with complex interwoven filaments?
  • A) Euglenoids
  • B) Brown Algae
  • C) Red Algae
  • D) Green Algae
  • Answer: C
  1. What is a characteristic of red algae in their cell walls?
  • A) Calcium carbonate
  • B) Silica
  • C) Chitin
  • D) Cellulose
  • Answer: A
  1. What is the unique characteristic of dinoflagellates’ cell walls?
  • A) Silica
  • B) Calcium carbonate
  • C) Interlocking cellulose plates
  • D) Impregnated with silicates
  • Answer: D
  1. Which protist phylum is considered closely related to zooflagellates?
  • A) Diatoms
  • B) Dinoflagellates
  • C) Euglenoids
  • D) Brown Algae
  • Answer: C
  1. What is the feeding stage of water molds?
  • A) Mycelium
  • B) Sporangium
  • C) Plasmodium
  • D) Hyphae
  • Answer: D
  1. What is the major economic and ecological significance of algae?
  • A) Source of cellulose
  • B) Major consumers in food chains
  • C) Production of bactericides
  • D) Source of algin, agar, and oxygen
  • Answer: D
Further Reading:  Vertebrate Axis Development


Frequently Asked Questions (FAQs) about Plants and Fungi

1. What is the significance of Protista in the biological classification?

  • Protista includes organisms that are neither plants nor animals. They are eukaryotes with a membrane-bounded nucleus and organelles.

2. Why are some protists called algae?

  • Some protists are called algae because, like plants, they perform photosynthesis and have chloroplasts. However, they lack proper roots, stems, leaves, and other plant structures.

3. How are organisms like euglenoids and dinoflagellates classified, and what was their initial classification?

  • Euglenoids, dinoflagellates, and similar organisms were initially classified in the kingdom Animalia but are now considered protists.

4. What are the characteristics of algae, and how do they differ from plants?

  • Algae are photosynthetic protists responsible for a significant portion of Earth’s photosynthesis. They differ from plants in their unicellular sex organs, with zygotes not protected by the parent body.

5. Can you name some types of algae and briefly describe their characteristics?

  • Algae types include euglenoids, dinoflagellates, diatoms, brown algae, red algae, and green algae. They exhibit diverse growth forms, from unicellular to multicellular structures.

6. Why are pigments important in the classification of algae?

  • Pigments, such as chlorophylls, carotenoids, xanthophylls, and phycoerythrin, play a crucial role in photosynthesis. Classification into algal phyla is often based on their pigment composition.

7. How do diatoms contribute to marine environments?

  • Diatoms, with their intricate glasslike cell walls, are major producers in marine environments and play a critical role in the water food cycle.

8. What distinguishes brown algae, and where are they commonly found?

  • Brown algae are multicellular and can range from a few centimeters to 75 meters. They are commonly found in cooler marine waters, especially along rocky shorelines.

9. Explain the importance of red algae in coral reefs.

  • Red algae contribute to coral reefs by integrating calcium carbonate in their cell walls, assisting in the building of coral reefs alongside coral animals.
Further Reading:  The Fruits with Higher Water Content

10. How do green algae relate to the evolutionary history of plants? – Green algae share pigments, energy reserves, and cell wall composition with plants, suggesting a common evolutionary ancestry. RNA sequencing supports their monophyletic relationship.

11. What distinguishes slime molds from fungi, and what is the feeding stage of a slime mold called? – Slime molds differ from fungi in having centrioles and producing cellulose. The feeding stage of a slime mold is called a plasmodium.

12. What is the significance of Oomycotes in history, particularly in the Irish potato famine? – Oomycotes, including Phytophthora infestans, caused the Irish potato famine in the 19th century by infecting potato tubers, leading to widespread starvation and mass migration.

13. How do water molds differ from fungi in terms of cell walls? – Water molds, or Oomycotes, have cellulose in their cell walls, distinguishing them from fungi, which have cell walls made of chitin.

14. What are some economic and ecological significances of algae? – Algae, including kelps, are edible and can help overcome food shortages. They are also sources of compounds like algin, agar, carrageenan, and bactericides, playing a vital role in aquatic food chains.


Wrapping up Plants and Fungi Tutorial

This tutorial provides a detailed exploration of protists, focusing on plant-like protists (algae) and fungi-like protists. The protist kingdom, Protista, encompasses eukaryotic organisms distinct from plants and animals.


  • Protists are eukaryotes with membrane-bounded nuclei and organelles.
  • Plant-like protists, known as algae, conduct photosynthesis, making them autotrophs.
  • Algae lack traditional plant structures but share similarities with plants.

Algae: Plant-like Protists

  1. Euglenoids (I): Plant-like protists with pigments resembling both plants and zooflagellates.
  2. Dinoflagellates (ii): Unicellular protists crucial in marine ecosystems, known for occasional blooms.
  3. Diatoms (iii): Major marine producers with intricate silica-based cell walls.
  4. Brown Algae (iv): Giant, multicellular protists prevalent in cooler marine waters.
  5. Red Algae (v): Multicellular, often contributing to coral reef structures.
  6. Green Algae (vi): Photosynthetic protists closely related to plants.

Importance of Algae

  • Algae contribute significantly to the aquatic food chain, produce oxygen, and offer valuable compounds.
  • Some algae, like kelps, are edible and contribute to overcoming food shortages.

Fungi-like Protists

  1. Slime Molds (i): Myxomycota with a unique feeding stage (plasmodium) studied for biological insights.
  2. Water Molds (ii): Oomycotes with historical significance, including the Irish potato famine.


This tutorial provides a comprehensive overview of plant and fungi-like protists, emphasizing their diversity, ecological roles, and historical significance. The content enhances understanding of these fascinating organisms in the context of their biological, ecological, and economic importance.