Kingdom Protista

Because they are all basic eukaryotes, the Kingdom Protista encompasses multiple phylogenetically diverse taxa that are linked together. Protists have membrane-bound organelles and a distinct nucleus, just as more complicated eukaryotes. They do not, however, have complex tissues like higher plants and animals. We’ll group them together into three categories: algae, protists, and slime moulds.

Algae are photoautotrophic plants with cell walls. Algae are difficult to classify, and there are various categorization schemes. We’ll refer to all eukaryotic photoautotrophic microbes as algae in this SparkNote. Green algae, red algae, brown and yellow-brown algae, dinoflagellates, and euglenoids are among the five groups. In the world’s oceans and lakes, algae play a critical role as producers.

Protozoa resemble animals. Protozoa are eukaryotic heterotrophic microbes that lack cell walls. Ciliates, kinetoplastids, and sarcodina are among them. Many protozoa are parasites that live inside other creatures. Slime moulds are unique microorganisms that resemble protozoa at times and fungus at others during their life cycles. Slime moulds are divided into two categories: cellular and acellular. Slime moulds live in wet soils and rotting plant debris.

 What are Protists?

Protists are any eukaryotes that are not fungi, animals, or plants. As a result, it’s an extremely varied group of species. The eukaryotes that comprise this kingdom, Kingdom Protista, share little in common other than a relatively simple arrangement. Protists can have extremely varied appearances. Some are as little and unicellular as an amoeba, while others are as massive and multicellular as seaweed. Multicellular protists, on the other hand, lack highly specialised tissues and organs. Protists are distinguished from other eukaryotes, such as fungi, mammals, and plants, by their basic cellular arrangement. There are an estimated 60,000 to 200,000 protist species, many of which have yet to be identified. Protists may exist in practically every liquid-water habitat. Many protists, such as algae, are photosynthetic and play an important role in ecosystems as primary producers. Other protists cause a variety of deadly human diseases, including malaria and sleeping sickness.

In 1866, Ernst Haeckel coined the term “protista.” Animal-like protozoa, plant-like protophyta (mainly algae), and fungus-like slime moulds and water moulds were the conventional classifications for protists based on their resemblance to plants, animals, or fungi. Traditional categories, which were mostly based on non-scientific qualities, have been supplanted by phylogenetic classifications (evolutionary relatedness among organisms). The older terminology, on the other hand, is still used informally to describe the broad characteristics of distinct protists.

Characteristics of Kingdom Protista

Protists are all eukaryotic organisms, which is their most distinguishing feature. They have a membrane-enclosed nucleus, which indicates they have a membrane-enclosed nucleus. The following are some of the other distinguishing characteristics of the Kingdom Protista:

• These are mainly aquatic and can be found in the soil or in moist regions.
• Although the majority of protist species are unicellular, there are a few multicellular protists, such as kelp. Kelp species can reach heights of more than 100 feet in some cases.
• These species’ cells feature a nucleus and membrane-bound organelles, just like every other eukaryote.
• They can be either autotrophic or heterotrophic. An autotrophic creature can survive by producing its own nourishment. In order to thrive, a heterotrophic creature must obtain nutrients from other species such as plants or animals.
• Members of this class show signs of symbiosis. Kelp (seaweed), for example, is a multicellular protist that protects otters from predators with its thick kelp. The otters, in turn, consume sea urchins, which eat kelp.
• Protists exhibit parasitism as well. Trypanosoma protozoa, for example, can cause sleeping sickness in humans.
• Cilia and flagella are used by protists to move about. The kingdom Protista has a few species with pseudopodia that assist them move.
• Asexual reproduction is used by Protista. Sexual reproduction is extremely rare and only occurs in situations of high stress.

Classification of Protista

It is classified into the following 3 groups:

Protozoa

Protozoa are single-celled creatures. Protozoans have been dubbed “animal” protists because they are heterotrophic and exhibit animal-like behaviours.

Parasitic protozoans can also be found in the cells of larger creatures. The majority of the members are not of a predetermined shape. An amoeba, for example, can alter shape endlessly, whereas a paramecium has a distinct slipper-like shape. Amoeba, paramecium, and euglena are some of the most well-known protozoans. Euglena is a free-living protozoa with chlorophyll, which implies it can manufacture its own food, unlike the other members of this category.

Protozoans can be classified into four groups:

Amoeboid protozoans are generally found in fresh or saline water basins. They feature pseudopodia (fake feet) that let them shift shape as well as capture and swallow food, for ex- Amoeba.

Flagellated protozoans — This group’s members have flagella, as the name implies. They can be both free-living and parasitic. For ex- Euglena.

Ciliated protozoans – These protozoans contain cilia all over their bodies that aid in motility and nourishment. They’re always in the water. For ex- Paramecium.

Sporozoans — These creatures get their name from the fact that they have a spore-like stage in their life cycle. For ex-  Plasmodium,is a malarial parasite.

Slime Moulds

Slime moulds are self-sustaining creatures (they feed on the dead and decaying matter). These are little organisms with a lot of nuclei. Slime moulds are usually identified by the presence of plasmodium aggregates, which are visible to the naked eye.

Chrysophytes, Dinoflagellates and Euglenoids

These belong to the kingdom Protista as well. These organisms are usually single-celled or multicellular. These photosynthetic organisms can be found in freshwater or marine lakes. They have a thick cell wall that makes them stand out.

Diatoms and golden algae are examples of chrysophytes. The presence of a stiff siliceous cell wall distinguishes them. The formation of diatomaceous earth is caused by the accumulation of cell wall deposits. Photosynthetic creatures are what they are.

Dinoflagellates are photosynthetic and come in a variety of colours depending on the pigment they contain. They emit bioluminescence and have been linked to red tide.

Plants and animals are linked by euglenoids. They don’t have a cell wall, but they do photosynthesis. In the absence of sunshine, they feed on small creatures as a heterotroph. A pellicle is a protein-rich coating that covers the outside of the body.  For example – Euglena, Trachelomonas .

Economic Importance of Protists

• Protists are the building blocks of the food chain.

• Protists are symbionts, which means they have a tight interaction with another species in which one benefits.

• Some protists create oxygen, which might be utilised to make biofuel.

• Many animals eat protists as their primary source of nutrition.

• Protists are occasionally harvested by humans for food and other industrial purposes.

• Whales eat phytoplankton as one of their only sources of food.

• Seaweed is an alga, which is a type of protist that looks like a plant.

• Shrimp and larval crabs are among the water organisms that feed zooplankton.

CONCLUSION

All eukaryotes that aren’t animals, plants, or fungi belong to the kingdom Protista.

Protista is an extremely diversified kingdom. It is made up of single-celled as well as multicellular organisms.

Protists are found all over the planet; as a group, they are both cosmopolitan and ubiquitous. Every species, on the other hand, has its own niches and microhabitats, and all protists are sensitive to changes in their environment to some extent. The only main issue preventing successful and widespread protist colonisation of virtually every ecosystem on Earth is the lack of sufficient nutrients and water, as well as sunlight for photosynthetic forms.