general characters and classification of protozoa pdf

General Characters And Classification Of Protozoa Pdf

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Phylum Protozoa: General characters and outline classification up to classes.

After completing this section you should be able to perform the following objectives. Protozoa are unicellular eukaryotic microorganisms lacking a cell wall and belonging to the Kingdom Protista. Although there are nearly 20, species of protozoa, relatively few cause disease; most inhabit soil and water.

General characteristics and classification of phylum Protozoa

Protozoa are single-celled organisms without cell walls. They are believed to be a part of the microbial world as they are unicellular and microscopic. There is a great deal to know about their classification, characteristics and more. As the primary hunters of the microbial world, protozoa help in continuing the equilibrium of bacterial, algal and other microbial life forms.

Would you like to write for us? Well, we're looking for good writers who want to spread the word. Get in touch with us and we'll talk They are named so because many species act like small animals. They search for and collect other microbes as food. Previously, protozoa were specified as unicellular protists possessing animal-like characteristics such as the capability to move in water.

Protists are a class of eukaryotic microorganisms which are a part of the kingdom Protista. Modern science has shown that protozoans refer to a very complex group of organisms that do not form a clade or monophylum. This has led scientists to give up the term protozoa.

Hence, the sub-kingdom Protozoa is not used today. Currently, protozoa are defined as single-celled, heterotrophic, or colonial eukaryotes possessing non-filamentous structures. Protozoa do not have a cell wall and therefore can have a variety of shapes. Nevertheless, some of the protozoans have a pliant layer, a pellicle, or a stiff shell outside the cell membrane. Protozoa vary in size and shape.

Their sizes range from 10 to 55 micrometers, but they can be as large as 1 mm. The largest protozoa are called xenophyophores, which can measure up to 20 centimeters in diameter. Protozoa prefer living in moist and aquatic habitats. Their cysts can be found in the bleakest parts of the ecosphere. Protozoa are found drifting in the oceans, seas, and freshwater. They are at the base of food chains. When in the cystic stage, protozoa can live in utmost temperatures or harsh chemicals, or without nutrients, water, or oxygen for a long time.

Being a cyst enables parasitic species to dwell on the host externally. This lets them transmit from one host to another. In the form of trophozoites, protozoa feed actively.

The transition of a trophozoite to a cyst is called encystation and the transition back to a trophozoite is called excystation. The mode of nutrition of protozoa is heterotrophic, and most species obtain food by phagocytosis. Phagocytosis is the process where the cell changes shape by sending out pseudopodia to make contact with food particles. Protozoa take food into the cell at a point called the cytostome.

The food is ingested by them and lysosomal enzymes digest the food. There are also certain types of protozoa that take in food by their cell membranes. Some others such as the amoeba, surround food and absorb it. Others have mouth pores into which they pull in food. Protozoans digest their food in spaces called vacuoles. Contractile vacuoles that are found in protozoa thriving in freshwater, excrete water that penetrates into the cells by osmosis.

While chewing down the food, protozoans produce and release nitrogen. Protozoa species move on their own by one of the three types of locomotor organelles such as flagella, cilia, or pseudopodia.

Protozoa reproduce by the method of binary fission or multiple fission. Some of the members reproduce by asexual mode, some by sexual means, and some by both. The protozoa group comprises more than 65, species. All the protozoan species belong to the kingdom Protista.

Many kinds of protozoa are symbionts. Some of the protozoan species are parasites and some are predators of bacteria and algae. Some examples of protozoans are dinoflagellates, amoebas, paramecia, and plasmodium. An amoeboid ameba or amoeba is a type of cell or organism that is capable of changing its shape, mainly by extending and retracting pseudopods.

They are normally found in the soil and in aquatic habitats. They move by using pseudopods. They typically ingest their food by phagocytosis. They extend their pseudopods to engulf a prey. They do not possess a mouth or cytostome. There is no specific place on the cell where phagocytosis takes place.

The food sources of amoebae differ. Some of them feed on bacteria and other protists. Some others feed on dead organic material. Some also feed by absorbing dissolved nutrients through vesicles.

The examples of amoeboids are Amoeba proteus, Chaos carolinense the giant amoeba , Naegleria fowleri the brain-eating amoeba , Entamoeba histolytica the intestinal parasite of commensals and humans , and Dictyostelium discoideum the multicellular social amoeba. Flagellates are organisms which have one or more whip-like organelles called flagella.

They may be solitary, colonial, free-living or parasitic. Parasitic forms live in the intestine or bloodstream of the host.

An example of a parasitic flagellate is Trypanosoma, which has an interesting life cycle as it uses two hosts; humans and tsetse fly. Many other flagellates like dinoflagellates live as plankton in the oceans and freshwater. Some flagellates are autotrophic while others are heterotrophs. Phytomastigophorea: The Phytomastigophorea includes protozoans that contain chlorophyll. They can produce their food photosynthetically, like plants.

Examples include Euglena and Dinoflagellates. Euglena is regarded as both an alga and a protozoan. Zoomastigophorea: It is the phylum commonly called zooflagellates. Zooflagellates include protozoans which are colorless.

They ingest organic substances by osmotrophy uptake of dissolved organic compounds through plasma membrane or phagotrophy engulfing prey in food vacuoles. They may be free-living, symbiotic, commensal, or parasitic. Examples include hypermastigids, holomastigotoides, and trichomonads. The ciliates are a group of protozoans which possesses hair-like organelles called cilia.

Cilia are used in swimming, crawling, attachment, feeding, and sensation. Most ciliates are heterotrophs. They eat organisms such as bacteria and algae. They sweep the food by their modified oral cilia into their oral groove mouth.

The food is moved with the help of cilia through the mouth pore into the gullet, which forms food vacuoles.

Some ciliates do not have a mouth and they feed by absorption osmotrophy , and some others are predatory and feed on other protozoa, especially ciliates.

Some ciliates also parasitize animals. Examples of ciliates include free-living forms like Paramecium caudatum, Stentor polymorpha, Vorticella campanula, and parasitic forms like Balantidium coli. There are three types of ciliated protozoa. They are free-swimming ciliates, crawling ciliates, and stalked ciliates.

All of them use cilia for locomotion and capturing food. Examples of free-swimming ciliates include Litonotus and Paramecium. Examples of crawling ciliates are Aspidisca and Euplotes. Sporozoans are non-motile, unicellular protists, usually parasites. These protozoans are also called intracellular parasites. An example is Plasmodium vivax, that causes malaria in humans. The earlier stage sporozoan forms show some movement.

They do not possess locomotor organelles in their later stage. Apicomplexa: The Apicomplexa, also called Apicomplexia, are a large phylum of parasitic protists. They are spore-forming unicellular parasites. Most of them have a unique organelle that is made up of a type of plastid called an apicoplast, and an apical complex structure.

The organelle is used by the organism for penetrating into a host cell. Flagella or pseudopods are found only in certain gamete stages. This group includes organisms like coccidia, gregarines, piroplasms, haemogregarines, and plasmodium.

The Major Classification and Characteristics of Protozoa

Protozoa also protozoan , plural protozoans is an informal term for a group of single-celled eukaryotes , either free-living or parasitic , which feed on organic matter such as other microorganisms or organic tissues and debris. In some systems of biological classification , Protozoa remains a high-level taxonomic group. When first introduced by Georg Goldfuss in , Protozoa was erected as a class within the animals, [6] and its etymology is literally "first animals". In later classification schemes it was elevated to a variety of higher ranks, including phylum , subkingdom and kingdom , and sometimes included within Protoctista or Protista. In a series of classifications proposed by Thomas Cavalier-Smith and his collaborators since , Protozoa has been ranked as a kingdom. Kingdom Protozoa, as defined in this scheme, does not form a natural group or clade , but a paraphyletic group or evolutionary grade , within which the members of Fungi , Animalia and Chromista are thought to have evolved.

Protozoa are eukaryotic microorganisms. Although they are often studied in zoology courses, they are considered part of the microbial world because they are unicellular and microscopic. Protozoa are notable for their ability to move independently, a characteristic found in the majority of species. Although most protozoa reproduce by asexual methods, sexual reproduction has been observed in several species. Most protozoal species are aerobic, but some anaerobic species have been found in the human intestine and animal rumen. Protozoa are located in most moist habitats. Free-living species inhabit freshwater and marine environments, and terrestrial species inhabit decaying organic matter.

Protozoa are a diverse group of organisms that are non-phototrophic, unicellular, eukaryotic microorganisms with no cell walls. Microbiology - Microbiology - Protozoa: Protozoa, or protozoans, are single-celled, eukaryotic microorganisms. Sub kingdom What are Microorganisms? Characteristics of Protozoa Unicellular Organization Since Protozoa are single celled they often rely on other organisms for some necessities Reproduction : Asexual: binary fission: cytoplasmic division follows mitosis, producing two … Still others have different shapes at different stages of the life cycle. The structure of Protozoa is similar to the eukaryotic cells. Protozoa is an informal term for single celled eukaryotes either free living or parasitic which feed on organic matter such as microorganisms or organic tiessus and debris.

9.1: Characteristics of Protozoa

Leishmania donovani— a digenetic parasite, primary host- man and secondary host — Sandfly Phlebotomus ; Disease- Kala-azar Dumdum fever L. Trichonympha — It is a symbiotic protozoan in the gut of termites, for cellulose digestion. Entamoeba histolytia — a monogenetic parasite in colon large intestine of man; causes Amoebiasis or Amoebic dysentry. Infective stage — Tetranucleated cyst. Mode of infection — contaminated food and water.

Gas gangrene- causative agents, Virulence factors, Pathogenesis, Clinical features, Laboratory diagnosis, Treatment, Prevention and Control. General Characteristics of phylum Protozoa Kingdom: Protista.

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