Question

How do Protists get their nutrients?

Answer 1

Hint: The organisms belonging to the Kingdom Protista are called Protists. They have a diverse range and vary from unicellular to multicellular organisms.

Complete answer:
Kingdom Protists is called the most diverse kingdom as it consists of all the eukaryotic organisms that are neither plants nor animals or fungi. They are the very first eukaryotic organisms on this planet. They may be unicellular or multicellular, autotrophic or heterotrophic, may live singular or in colonies. They are found in moist and aquatic habitats and reproduce mostly through the asexual mode of reproduction. They can be microscopic or macroscopic and have complex organelles like mitochondria and lysosomes. They can be classified into five major groups- Chrysophytes, Dinoflagellates, Euglenoids, Slime molds, and Protozoans.
To study their nutrition, we classify them into three categories- Plant Like Protists, Fungi like Protists, and Animals like Protists.

1)Plant-like Protists- These protists resemble plants in their features and include organisms from euglenoids, diatoms, and dinoflagellates. They have chloroplasts in their cells and thus can perform photosynthesis in the presence of sunlight to prepare their own food. They are also called photosynthetic protists and are autotrophic in nature. Example- Algae, Seaweeds like Kelp, Euglena, Diatoms, etc.

2)Fungi-like Protists- These protists resemble fungi in their features and include organisms from Slime Moulds. They have a cellulosic cell wall and reproduce through spore formation. They generally show no movement but might develop false feet called Psuepods at a later stage. They are heterotrophic in nature and thus obtain their food from an outside source. They are saprophytes that obtain their nutrients by feeding on dead and decaying organic matter. These protists can be classified into two categories- water molds and slime molds.

3)Animal-like protists- These protists resemble animals in their features and include organisms from protozoans. They are unicellular eukaryotes and are heterotrophic in nature. Their cells contain membrane-bound organelles and are mobile. They obtain their food from the outside by ingesting it in their body. They have two common methods to obtain food, which are-

Endocytosis- These protists swallow their food by their cell membrane and are also called phagotrophs. The food to be ingested- is surrounded by the cell membrane, and a food vacuole is generated near it. The toxins released paralyzes the substance, and then it is engulfed inside through the pseudopodium straight to the food vacuole. From the food vacuole, it moves to the cytoplasm of the cell where- digestion occurs. Example- Amoeba.
Filter-feeder mechanism- These protists absorb food from their environment by using their cilia, flagella, or tails and are also called organotrophs. These organs are present near the mouth of their body. They move or whip their organs, constantly back and forth, to generate an air current near the food substance. The rapid movement brings the protists near the food, and the air current filters the food, which is then absorbed by the body. Example- Paramecium uses its cilia to absorb food.

4)Some Protists can obtain their nutrition by being a parasite on the host body. These protists resemble the animal-like and fungi-like protists and can also cause several diseases. Example- Plasmodium, Trypanosoma, Leishmania, etc.

5)Protists can also be mixotrophic, which means they are both- autotrophic as well as heterotrophic. They can utilize both or either way to obtain their food at a time. Example- Many dinoflagellates.

Note: Since the Kingdom Protista has all the organisms that do not fit into other Kingdoms like- Plantae, Animalia, and Fungi, they exhibit all modes of nutrition. Their resemblance to all these kingdoms makes them a connecting link between them.