Characteristics of Kingdom Protista
All single-celled eukaryotes are classified as Protista. On the other hand, the kingdom’s borders are not clearly defined. The phylum Protista is primarily an aquatic one. Plants, animals, and fungi are all connected to this kingdom. Like other eukaryotes, the protist cell body has a very well nucleus as well as other membrane-bound organelles.
Protista
Some have flagella or cilia, while others aren’t . Cell fusion and zygote development are used by protists to reproduce both asexually and sexually. It’s possible that it’s photosynthetic or holotropic. Saprotrophic, parasitic, and symbionts are all possibilities. Some, on the other hand, may have a mixotrophic diet (holotropic + saprobic). Phytoplanktons are photosynthetic protists that float in the water. Zooplanktons are holozoic protozoans that float freely.
Unicellular Protists are grouped together.
Unicellular protists can be divided into three categories:
Protists that are photosynthetic. Dinoflagellates, Diatoms, and Euglenoids are some examples.
Consumer Protists are a type of consumerist. Slime moulds or Myxomycetes Protozoan Protists are two examples. Zooflagellate, Sarcodina, Sporozoa, and Ciliata are some examples.
Protist Life Cycles with Zygotic Meiosis
What we mean by life cycle is a series of events that occur between any particular phase in one generation and a similar phase in the following generation. It’s found in several dinoflagellates and cellular slime moulds (for example, ceratium and gymnodinium; von Stosch, 1973).
The zygote is in the form of a two-nucleotide repeat. Meiosis is the most common way for it to divide (also called zygotic meiosis). These give birth to 1n chromosome-containing vegetative cells. Mitosis is a cell division process that happens regularly in these cells. The number of chromosomes in the daughter cells is retained at 1n. Gametes are produced by certain vegetative cells. When these gametes fertilise each other, a zygote is created, and the life cycle is finished.
Protists in Major Groups
Chrysophytes
The diatoms and golden algae make up this category (desmids). They can be found in both freshwater and marine habitats. They are really little. These organisms float in water currents in a passive manner (plankton).
Dinoflagellates
These organisms are usually photosynthetic and marine. They come in a variety of colours, including yellow, green, brown, blue, and red. The primary pigments contained in their cells impact and determine their colour. On the outside of the cell wall are rigid cellulose plates. Flagella are frequently seen in a furrow between the wall plates, one longitudinally and the other transversely.
Euglenoids
These are generally creatures that live in freshwater. They can be found in stagnant water. They are devoid of a cell wall. Instead, they have a protein-rich coating called pellicle that makes their bodies flexible. There are two flagella on them. The first is a short one, while the second is a long one. A bulge called the paraflagellar body connects the two flagella.
Euglena is a link that connects animals and plants. Euglena’s nutrition is mixotrophic; when light is available, it photosynthesizes; when darkness prevails, it saprophytism, absorbing food from the surrounding water.
Moulds of Slime
Slime moulds are protists that feed on the things they come into contact with. Their bodies can eat organic stuff by moving through decomposing twigs and leaves. Under optimum conditions, they form a Plasmodium aggregate that can expand and spread over many feet. In unfavourable conditions, the plasmodium grows and produces fruiting bodies with spores at their tips.
True walls exist within the spores. Air currents disseminate the spores. They are particularly resistant to environmental changes. They have the ability to live for many years, even under harsh situations.
Protozoans
Protozoans are all heterotrophic, meaning they live as predators or parasites. Animal relatives are thought to be their ancestors. Protozoa are divided into four categories:
Protozoans that have flagella for locomotion are known as flagellated protozoans. Free-living aquatics, parasites, commensals, and symbionts are all possibilities. Zooflagellates are mostly uninucleate, although they can also be multinucleate.
Amoebic Protozoans produce pseudopodia, which are protoplasmic outgrowths that last for a few days. These are employed for movement as well as ingesting food. Sarcodines are primarily free-living creatures that can be found in freshwater, sea water, and damp soil.
Endoparasites: Sporozoans are all endoparasites. Some sporozoans, such as Eimeria, cause serious infections in birds, such as coccidiosis. Nutrition has a parasitic nature (absorptive). Phagotrophy is a rare condition.
Ciliated Protozoans are protozoan protists that are ciliated. During one or more stages of their life cycle, these organisms produce a large number of cilia. Cilia are used for movement and food driving. Ingestion and egestion take place in separate areas. An oral groove, cytostome (mouth), and gullet make up the ingestion zone.
Conclusion
Protists are eukaryotic organisms that are neither plants, animals, nor fungi but are simple eukaryotic organisms. Protists are usually unicellular, however they can also be found in colonies of cells. The majority of protists live in water, moist terrestrial settings, or as parasites.
Protists have a few qualities in common.
- They have a nucleus, which makes them eukaryotic.
- The majority of people have mitochondria.
- It’s possible that they’re parasites.
- All of them prefer wet or wet conditions.