There are diverse organisms in this world segregated into different groups or various kingdoms.We, humans, belong to the kingdom Animalia. Likewise, other living organisms, like plants, belong to the kingdom Plantae, and bacteria belong to the kingdom Monera.Today, let’s discuss the kingdom Protista. This kingdom is said to have evolved over 1.5 billion years ago. All the protists may look like single-cell bacteria or an organism that seems like fungi, but they don’t fall under either Monera or Fungi kingdoms. They instead fall under the Protista kingdom. Let’s discuss what these are and the types of protists in this article.What are Protista?There are five biological kingdoms, namely Animalia, Plantae, Protista, Fungi, and Monera. Living organisms are classified into these five kingdoms based on various factors like how they eat food, whether they are single or multicellular, how they reproduce, and so on. Let’s dive deeper into facts about protists.You might have heard of eukaryotes. Kingdom Protista has single or individual cells or multiple eukaryotic cells. Protists are neither animals nor plants. They either have a single-celled body or may also be found in a colony of cells. Many of the protists, like algae and protozoa (amoeba), survive in damp environments or in water. These also live as parasites and feed upon plants or dead decomposing animals. ‘Protistos’ is a Greek word that means ’the very first’. The term Protista is derived from this word.The cell body of the protists consists of a nucleus that is bound to organelles. Some protists have a structure and organs that aid in locomotion, like cilia or flagella. Protists are a link between animals, plants, and fungi. Scientists believe that those three kingdoms have a common ancestor (hypothetical organism) from which they diverged billions of years ago, and the ancestor is probably a protist.Protists are considered by scientists to be the first eukaryotic forms of life and ancestors of other kingdoms, excluding kingdom Monera. Many protists relate more to other eukaryotes than one another and are hence renamed Eukarya. Many scientists abandoned the name Protista. Kingdom Protista is very large, and the size of a protist may range from some micrometers to some hectares.Organisms Included In ProtistaProtista kingdom is majorly classified into three sub-categories, namely protozoa (animal-like), slime molds (fungi-like), and algae (plant-like). Let’s discuss these types of protists in detail below.Protozoa/Protozoans (animal-like): These are unicellular and heterotrophic. They also show animal-like behavior and were called animal-like protists. Protozoans are the parasites that live in the red blood cells of larger-sized animals and eat off pre-digested food. Amoeba, Euglena, and paramecium are famous examples of this group. Protozoans do not have a specific shape. An amoeba can change its shape, but a paramecium cannot and is shaped like a slipper. Among these, Euglena is one of the free-living photosynthetic protists that makes its food using chlorophyll.Cellular slime molds (fungi-like): Next in different types of protists come cellular slime molds. Slime molds are organisms that are saprophytic, meaning they eat the dead and decaying organic material. These slime molds have many nuclei and are very small. There are aggregates named Plasmodium falciparum present in these, which is how they are characterized.Algae (plant-like): These types of protists are usually found in freshwater resources or marine lakes and are single-celled or multicellular organisms. We all have seen different algae on water bodies around us, like red algae or green algae. These algae produce food using photosynthesis. Seaweed is an alga that is also a protest. Plant-like protists are mainly subdivided into three categories, namely, Chrysophytes, Dinoflagellates, and Euglenoids, and are characterized by a still cell body wall. Chrysophytes have two groups, golden algae, and diatoms, and are known for their hard siliceous cell walls. Dinoflagellates are multicolored protists due to the pigments present in them. They perform photosynthesis and are also known to show bioluminescence. They also cause the annual Florida red tide. Euglenoids link plants and animals together. Although they don’t have a cell wall, they do perform photosynthesis. They act as heterotrophs in the absence of sunlight by feeding on smaller organisms. Examples are Euglena and Trachelomonas. Charophytes are the closest and most similar to land plants.Characteristics Of ProtistaOne thing that is common in all protists is that they are all eukaryotic organisms. Being eukaryotic means having a membrane-enclosed nucleus. Read some other vital characteristics of these protists.Every protist has a mitochondrion. Protists are usually aquatic and can be found in damp places. Although many protists are unicellular organisms, organism like kelp is a part of multicellular protists. They can either be autotrophs (make their food) or heterotrophs (feed on another organism like pathogens) in nature. You can observe parasitism in protists. Humans may suffer from sleeping sickness due to protists like Trypanosoma protozoa.Flagella and cilia are used by these organisms for locomotion. Some of these protists also have pseudopodia or false feet, if not flagella or cilia, which help them move around. Most protists reproduce by asexual means of binary fission, multiple fission, plasmotomy, budding, or spore formation. For example, amoebas reproduce by binary and multiple fissions. Sexual reproduction only occurs in stressful times.The Ecological Importance Of ProtistaMany people believe that the whole life cycle depends on a protist as these eukaryotes are an essential part of ecology. Many people speculate that if these protists disappear, the whole ecology would be disturbed. Let’s see what the ecological importance of the kingdom Protista is.Protists observe symbiosis. This means helping their host in exchange for their survival. For example, thick kelp protects otters from predators. In return, the otters eat sea urchins that otherwise feed on the kelp. Plant-like protist organisms are said to produce almost half of the Earth’s oxygen through the process of photosynthesis. The nutrients that we need to live are recycled and decomposed by protists.The oxygen that these species produce can be used as biofuel. Phytoplankton, a protist, is one of the only food sources for some whales. Protists that are autotrophs carry out the world’s 40% photosynthesis, thus helping maintain the world’s carbon levels. Mixotrophs are a very important part of the aquatic food cycle.Bacteria and microbes are the food of many protists, and hence they help control the population of these harmful bacteria and microbes.
There are diverse organisms in this world segregated into different groups or various kingdoms.
