Kingdom Protista: Chrysophytes and Dinoflagellates | Biology Class 11 - NEET PDF Download

Protista is a kingdom that includes all single-celled eukaryotes. However, the boundaries of this kingdom are not well defined, as some organisms may be considered protists by some biologists but classified as plants, animals, or fungi by others. 

Protists are primarily aquatic organisms and form a link between other kingdoms such as plants, animals, and fungi. Protists are eukaryotes, which means their cells have a well-defined nucleus and other membrane-bound organelles. Some protists also have flagella or cilia for movement. Protists reproduce both asexually and sexually, involving processes such as cell fusion and zygote formation.

An organism of Kingdom Protista

Chrysophytes

Chrysophytes are a group of microscopic protists that include diatoms and golden algae (desmids). They are found in both freshwater and marine environments and are often part of the plankton, floating passively in water currents. Most chrysophytes are photosynthetic, meaning they use sunlight to produce food.

(i) Diatoms

• Diatoms are a type of chrysophyte that have unique cell walls made of two thin, overlapping shells, resembling a soap box.

Diatoms

• These cell walls are embedded with silica, making them indestructible and durable.
• Over billions of years, diatoms have left behind large deposits of their cell walls in their habitats, known as "diatomaceous earth".
• Diatomaceous earth is gritty in texture and has various uses, such as in polishing, filtration of oils and syrups, and as an insecticide.
• Diatoms are also important as primary producers in the oceans, contributing to the production of oxygen and serving as the base of the marine food chain.

Economic Importance of Diatoms 

• Diatoms are very important photosynthesizers. About half of all the organic matter synthesized in the world is believed to be produced by them. Though microscopic, diatoms are an important source of food to aquatic animals. A 60-tonne blue whale may have 2 tonnes of plankton in the gut which is mostly diatoms. 
• The oils extracted from some fishes and whales are actually the ones produced by diatoms. 
• Diatomite deposits are often accompanied by petroleum fields. Much of the petroleum of today is probably due to decayed bodies of the past diatoms. 
• Diatomite is porous and chemically inert. It is, therefore, used in the filtration of sugar, alcohols oil, syrups and antibiotics. 
• Diatomite is employed as a cleaning agent in toothpaste and metal polishes. 
• Diatomite is added to paints for enhancing night visibility. 
• Diatomite is employed as insulation material in refrigerators, boilers and furnaces. 
• Diatomaceous earth is added to make soundproof rooms. 
• Diatomite is a good industrial catalyst. 
• Diatomite is a source of water glass or sodium silicate. 
• Diatoms are very good pollution indicators.

(ii) Golden Algae (Desmids)

• Golden algae, also known as desmids, are another group of chrysophytes. Desmids are unicellular green algae. 

Golden algae

• They are characterized by their unique cell shape, which can be highly symmetrical with intricate patterns.
• Desmids are often found in freshwater environments, such as ponds and lakes.
• Like diatoms, desmids are also photosynthetic and contribute to the overall productivity of aquatic ecosystems.
• They are mainly found in fresh water and are usually indications of clean (unpolluted) water.
• Sexual reproduction occurs by 'conjugation' similar to that of Spirogyra. 

Economic Importance of Desmids (Golden Algae) 

• They are important in aquatic ecosystems as they serve as primary producers, contributing to the food chain and supporting the growth of other organisms.
• Desmids are also used in ecological studies as bioindicators to assess the health and quality of freshwater habitats.
• Some species of desmids are commercially used as live food in aquaculture for fish and shrimp farming.
• Desmids have also been studied for their potential in bioremediation, as they have the ability to absorb and accumulate heavy metals from polluted water bodies, helping to detoxify the environment.
• Additionally, desmids are used in research and education as model organisms to study cell structure, reproduction, and other biological processes.

Dinoflagellates

Dinoflagellates are a group of microscopic protists that are mostly found in marine environments. They are photosynthetic organisms, meaning they use sunlight to produce food. Dinoflagellates exhibit a wide range of colors, appearing yellow, green, brown, blue, or red, depending on the pigments present in their cells. They have a unique cell wall structure with stiff cellulose plates on the outer surface.

Examples. Glenodinium, Peridinium, Gymnodinium. Gonyaulax,Ceratium, Noctiluca.

Dinoflagellate

(i) Morphology and Flagella in Dinoflagellates

• Dinoflagellates typically have two flagella, which are whip-like appendages used for movement.
• One flagellum is oriented longitudinally along the cell, while the other is positioned transversely in a furrow between the cellulose plates of the cell wall.
• The presence of flagella allows dinoflagellates to exhibit various types of movements, such as spinning and tumbling.

(ii) Red Dinoflagellates and Red Tides

• Some dinoflagellates, particularly those with red pigments, can undergo rapid multiplication, resulting in a phenomenon known as "red tide".
• Red tide refers to the massive proliferation of dinoflagellates, often making the sea appear red in color.
• Red dinoflagellates, such as Gonyaulax, are known to release toxins into the surrounding water, which can have harmful effects on marine animals, including fishes.
• The toxins released during red tides can lead to fish kills and other ecological disruptions.

Economic Importance of Dinoflagellates 

• Some species of dinoflagellates are important in commercial fisheries as they form the base of marine food chains, providing food for fish and other marine organisms.
• Dinoflagellates are also used in aquaculture as live food for larval stages of various marine organisms, including fish, shrimp, and mollusks.
• Certain species of dinoflagellates are used in biotechnology for their ability to produce bioluminescence, which has applications in medical research, environmental monitoring, and food safety testing.
• Dinoflagellates are also used in the production of marine toxins, which are used in research, pharmaceuticals, and other applications.
• Some dinoflagellates are harmful and can cause "red tide" events, which are harmful algal blooms that can result in the death of marine organisms and impact fisheries and aquaculture industries.
• Dinoflagellates are also used in the study of marine ecology and as indicators of environmental changes, such as water quality and climate change.

FAQs (Frequently Asked Questions)

Q. What are Protists?

Protists are a diverse group of organisms that can be either single-celled or multicellular, possessing a nucleus and specialized cellular machinery called cell organelles. They can exhibit various life processes and can be autotrophic (such as algae), heterotrophic (like Amoeba), or even parasitic (such as Trypanosoma protozoa).

Q. How are Protists classified?

Protists are classified into 5 subdivisions based on their characteristic features, which are:

1. Chrysophytes
2. Dinoflagellates
3. Euglenoids
4. Slime molds
5. Protozoans

Q. Provide some examples of Protists.

Examples of Protists include Amoeba, Paramecium, Euglena, Plasmodium, and others.

Q. Are all Protists unicellular?

No, not all Protists are unicellular. Some Protists, such as molds and algae, are multicellular, composed of more than one cell. However, organisms like Amoeba, Paramecium, and Euglena are unicellular and belong to the kingdom Protista.

Q. Outline the characteristics of Kingdom Protista.

• All protists are eukaryotic, possessing a membrane-enclosed nucleus and other cell organelles.
• Most protists are aquatic, while some can be found in moist and damp environments.
• Most protists are unicellular, although some, like giant kelp, are multicellular.
• Protists can be autotrophic or heterotrophic in nature, and parasitism and symbiosis can also be observed in some.