The kingdom Protista belongs to a eukaryotic organism that is not a fungus, a plant, or an animal. We find that Protists differ from each other, and we can see them through a microscope. They are unicellular like an amoeba, and some are multicellular like seaweed. The large and multicellular Protists do not have specialized organs. As eukaryotes, Protists differ in the cellular organization from fungi, animals, and plants. Scientist has found around 60,000 to 200,000 species of Protists. And many of them are still unknown. Protest can live in any environment because they need moisture to live. They are photosynthetic and vital for primary producers in our ecosystem, like algae. Many other Protists cause diseases such as malaria, diarrhoea and sleeping sickness.
The term Protists was first coined by a scientist, Ernest Haeckel, in 1866. The Protists are classified based on their similarity to plants, animals, fungi, protozoa. Some of these are like each other, such as protozoa, algae, & slime moulds and water molds, which look like fungi. Each group of Protists consists of several subgroups. These traditional subdivisions are based on non-scientific traits and replaced by phylogenetic classifications. This is the evolutionary relationship between organisms.
The Protists – Eukaryotes:
Protists are eukaryotic organisms that do not belong to the animal or plant kingdoms. They are similarities based on the unicellular organism as found in nature everywhere. Additionally, they are discovered in the colony formation of the cell. Protists usually live-in water, damp environments or even parasites.
Protist has its roots in the Greek word “Protistos”, meaning “the very first”. The organism of these cells contains a nucleus that is bound to the organelle. Some of their structures and features like locomotion – cilia and flagella. These organisms are the first eukaryotic forms of life. And a predecessor to plants, animals, and fungi.
Kingdom Protista Characteristics:
Kingdom Protista is classified as eukaryotes since they belong to the Eukarya Domain. The bacterial nucleus has a membrane surrounding its nucleus. It contains DNA, like the nucleus of other eukaryotes. They also have other membrane-bound organelles such as mitochondria and endoplasmic reticulum. Most Protists are unicellular & Some are multicellular. The different food acquisition and breeding methods of protists make them so diverse.
Protists are like plants because they have a cell wall and chloroplasts. Chloroplasts use to make photosynthesis in these cells. Besides a nucleus, Protists have special organelles in their cytoplasm. The endoplasmic reticulum is essential for protein synthesis. The Golgi apparatus is necessary for the exocytosis of cellular molecules. Many Protists have lysosomes which are helpful in the digestion of organic material. Protists also have common characteristics with animal cells because they have mitochondria that provide energy to the cell.
Locomotion of Protists:
Some Protists are immobile, while others show locomotion in different ways. Some Protists have flagella and cilia. These organelles are protrusions formed from a particular group of microtubules that move to propel Protists through a moist environment. Other Protists move using a temporary expansion of the cytoplasm known as pseudopodia. These extensions are also valuable to allow Protists to capture other feeding organisms.
Reproduction in Parasites:
The most common method of reproduction among Protists is asexual reproduction. Sexual reproduction is possible, but it usually occurs only during stress. Some Protists reproduce by double or many divisions. Others reproduce by budding or sporulation. In sexual reproduction, gametes are produced through meiosis. And combine during fertilization to produce new individuals. Other Protists, such as algae, show alternation of generations. That switch between haploid and diploid stages in their life cycle.
The members of the Kingdom Protista show different ways to get food. Some are photosynthetic autotrophs, which mean they are self-feeding. But They can also use sunlight to produce carbohydrates for nutrition. Other Protists are heterotrophs that feed by ingesting other organisms according to the process of phagocytosis. This is the process of trapping the particles and digestion. But, other Protists feed by ingesting nutrients from their environment. Some Protists can take up both photosynthetic and heterotrophic nutrients.
Classification of Kingdom Protista:
The kingdom Protists is divided into three groups, and these groups are like Protists.
Plant Protists – Similarity of Characters:
Plant-like organisms that are also photosynthetic organisms are classified into three sub-types.
- Dinoflagellates – Subtype of Kingdom Protista:
The group of Dinoflagellates has 1000 species of photosynthetic Protists. It belongs to a division (Pyrrophyta) and class (Dinophyceae).
These are photosynthetic, motile, biflagellate Protists and found in the marine. Dinoflagellates have different colourpigments, but some of them emit light.This phenomenon is called bioluminescence. The scenario of red tide is visible during the rapid multiplication of organisms. But sometimes, it kills marine life by producing toxins. They have both sexual and asexual methods for reproduction. —for Example, Gonyaulax, Noctiluca, etc.
These are the diatoms and golden algae of the plant world. The members of this sub-division show the following characteristics.
These organisms are unicellular and float on marine water. They are photosynthetic, and their cell wall is made up of pectin & silica. They have both sexual and asexual methods for reproduction. For example, Diatoms, Desmids, golden algae, etc.
These are unicellular and share the characteristics of both plants and animals. These are autotrophic in nutrition, such as Euglena and found in stagnant water. They have flexible bodies because they have a protein-rich layer called a pellicle. Their food is stored in pyrenoids that are proteinaceous granules.
Fungi (Slime Mold) – Subtype of Kingdom Protista:
Fungi have the character of both animals and fungi. Thus, combined are called animal fungi. They are found on dead leaves and moist terrestrial habitats. They are saprophytic in nutrition and reproduce by sexual and asexual methods. The presence of plasmodium aggregates usually identifies slime moulds, which are visible to the naked eye.
Animal (Protozoan) – sub – Type of Kingdom Protista:
They are single cellular and heterotrophic organisms. The animal behaviour of these Protists referred to them as protists. Thus, they are present in the kingdom Protista. These organisms live in the cell of the larger organism. They are divided into four sub-types. Read it below!
- Amoeboid Protozoan:
Amoeboid protozoans are found in freshwater, soil and saltwater. As in amoeba, they move through the pseudopodia. They have different members in their groups, such as Entamoeba histolytica & E. gingivalis. Thus, they cause various digestive and oral diseases when engulfed through polluted water.
- Flagellated Protozoan:
Flagellated protozoans are both free-living and parasitic in nature. The members of this group are as here. Trypanosome species, Leishmania species and Giardia species cause different diseases, e.g., Euglena.
- Ciliated Protozoan:
A ciliated protozoan is an aquatic organism. Ciliated protozoans have cilia on their body that help them in locomotion. They show nuclear dimorphism, E.g., paramecium.
These sporozoans are endo-parasites. They have an infectious spore stage in their life cycle. They move with the help of the locomotive organs called cilia, flagella, & pseudopodia. For example, Plasmodium, monocytes, etc.
Economic Importance of Protists:
The members of the kingdom Protista play a vital role in the aquatic food chain. But they are the pollution indicator for the environment. It is possible to use some Protists in the production of cosmetics, drugs, and vitamins. Animals eat them as their primary source of nutrition, while humans harvest them for food. Some Protists are produced bio-fuel, and some are produced oxygen. Phyto-plankton is a good source for whales. Different creatures such as shrimp and crab feed zooplankton.