Which Characteristic Is Used To Categorize The Different Kinds Of Animal-like Protists?

Cell Structure, Metabolism, and Move

Protists are an incredibly diverse set of eukaryotes of various sizes, cell structures, metabolisms, and methods of movement.

Learning Objectives

Describe the metabolism and structure of protists, explaining the structures that provide their motion

Cardinal Takeaways

Key Points

• Protist cells may contain a unmarried nucleus or many nuclei; they range in size from microscopic to thousands of meters in surface area.
• Protists may take animal-like cell membranes, plant-similar cell walls, or may be covered by a pellicle.
• Some protists are heterotrophs and ingest food by phagocytosis, while other types of protists are photoautotrophs and store energy via photosynthesis.
• Most protists are motile and generate movement with cilia, flagella, or pseudopodia.

Key Terms

• amorphous: defective a definite form or clear shape
• multinucleate: having more one nucleus
• pellicle: cuticle, the hard protective outer layer of certain life forms
• taxis: the motion of an organism in response to a stimulus; similar to kinesis, but more direct
• phagocytosis: the process where a prison cell incorporates a particle by extending pseudopodia and drawing the particle into a vacuole of its cytoplasm
• phagosome: a membrane-bound vacuole inside a cell containing foreign material captured past phagocytosis

Cell Construction

The cells of protists are amidst the most elaborate and diverse of all cells. Most protists are microscopic and unicellular, simply some true multicellular forms exist. A few protists live as colonies that behave in some ways equally a group of free-living cells and in other ways as a multicellular organism. Even so other protists are equanimous of enormous, multinucleate, unmarried cells that look like baggy blobs of slime, or in other cases, similar to ferns. Many protist cells are multinucleated; in some species, the nuclei are different sizes and have distinct roles in protist cell function.

Single protist cells range in size from less than a micrometer to thousands of foursquare meters (behemothic kelp). Animal-like prison cell membranes or plant-like cell walls envelope protist cells. In other protists, glassy silica-based shells or pellicles of interlocking protein strips encase the cells. The pellicle functions like a flexible glaze of armor, preventing the protist from external impairment without compromising its range of movement.

Metabolism

Protists exhibit many forms of nutrition and may exist aerobic or anaerobic. Protists that store energy by photosynthesis belong to a group of photoautotrophs and are characterized by the presence of chloroplasts. Other protists are heterotrophic and consume organic materials (such as other organisms) to obtain nutrition. Amoebas and another heterotrophic protist species ingest particles by a procedure called phagocytosis in which the prison cell membrane engulfs a food particle and brings information technology in, pinching off an intracellular membranous sac, or vesicle, called a food vacuole. The vesicle containing the ingested particle, the phagosome, then fuses with a lysosome containing hydrolytic enzymes to produce a phagolysosome, which breaks down the food particle into small molecules that lengthened into the cytoplasm for utilise in cellular metabolism. Undigested remains ultimately go out the prison cell via exocytosis.

Protist metabolism: The stages of phagocytosis include the engulfment of a food particle, the digestion of the particle using enzymes contained inside a lysosome, and the expulsion of undigested materials from the cell.

Subtypes of heterotrophs, chosen saprobes, absorb nutrients from dead organisms or their organic wastes. Some protists function equally mixotrophs, obtaining nutrition past photoautotrophic or heterotrophic routes, depending on whether sunlight or organic nutrients are available.

Movement

The majority of protists are motile, just different types of protists have evolved varied modes of movement. Protists such as euglena accept ane or more flagella, which they rotate or whip to generate move. Paramecia are covered in rows of tiny cilia that they beat to swim through liquids. Other protists, such at amoebae, grade cytoplasmic extensions called pseudopodia anywhere on the cell, anchor the pseudopodia to a surface, and pull themselves forrard. Some protists can motility toward or away from a stimulus; a motion referred to as taxis. Protists accomplish phototaxis, movement toward low-cal, by coupling their locomotion strategy with a lite-sensing organ.

Different types of motility in protists: Protists use various methods for transportation. (a) A paramecium waves pilus-like appendages called cilia. (b) An amoeba uses lobe-like pseudopodia to ballast itself to a solid surface and pull itself frontwards. (c) Euglena uses a whip-similar tail called a flagellum.

Protist Life Cycles and Habitats

Protists live in a broad multifariousness of habitats, including most bodies of h2o, every bit parasites in both plants and animals, and on dead organisms.

Learning Objectives

Depict the habitats and life cycles of various protists

Key Takeaways

Key Points

• Slime molds are categorized on the ground of their life cycles into plasmodial or cellular types, both of which end their life cycle in the class of dispersed spores.
• Plasmodial slime molds form a single-celled, multinucleate mass, whereas cellular slime molds form an aggregated mass of separate amoebas that are able to migrate as a unified whole.
• Slimes molds feed primarily on bacteria and fungi and contribute to the decomposition of expressionless plants.

Central Terms

• haploid: of a cell having a single fix of unpaired chromosomes
• sporangia: an enclosure in which spores are formed (also called a fruiting body)
• plasmodium: a mass of cytoplasm, containing many nuclei, created past the aggregation of amoeboid cells of slime molds during their vegetative stage
• diploid: of a cell, having a pair of each blazon of chromosome, one of the pair being derived from the ovum and the other from the spermatozoon

Life Cycle of Slime Molds

Protist life cycles range from uncomplicated to extremely elaborate. Certain parasitic protists have complicated life cycles and must infect dissimilar host species at dissimilar developmental stages to consummate their life cycle. Some protists are unicellular in the haploid form and multicellular in the diploid form, which is a strategy also employed by animals. Other protists have multicellular stages in both haploid and diploid forms, a strategy called alternation of generations that is too used by plants.

Plasmodial slime molds

The slime molds are categorized on the basis of their life cycles into plasmodial or cellular types. Plasmodial slime molds are composed of large, multinucleate cells and move along surfaces like an baggy blob of slime during their feeding stage. The slime mold glides along, lifting and engulfing food particles, especially bacteria. Upon maturation, the plasmodium takes on a net-similar appearance with the power to course fruiting bodies, or sporangia, during times of stress. Meiosis produces haploid spores within the sporangia. Spores disseminate through the air or water to potentially land in more favorable environments. If this occurs, the spores germinate to course amoeboid or flagellate haploid cells that tin combine with each other and produce a diploid zygotic slime mold to complete the life cycle.

Plasmodial slime mold life cycle: Haploid spores develop into amoeboid or flagellated forms, which are and so fertilized to form a diploid, multinucleate mass called a plasmodium. This plasmodium is net-like and, upon maturation, forms a sporangium on top of a stem. The sporangium forms haploid spores through meiosis, later which the spores disseminate, germinate, and brainstorm the life cycle anew. The brightly-colored plasmodium in the inset photo is a single-celled, multinucleate mass.

Cellular slime molds

The cellular slime molds part as independent amoeboid cells when nutrients are abundant. When food is depleted, cellular slime molds aggregate into a mass of cells that behaves as a single unit called a slug. Some cells in the slug contribute to a 2–3-millimeter stalk, which dries up and dies in the procedure. Cells atop the stalk form an asexual fruiting body that contains haploid spores. As with plasmodial slime molds, the spores are disseminated and tin germinate if they land in a moist environment. One representative genus of the cellular slime molds is Dictyostelium, which commonly exists in the damp soil of forests.

Cellular slime mold life cycle: Cellular slime molds may engage in 2 forms of life cycles: every bit solitary amoebas when nutrients are arable or as aggregated amoebas (inset photograph) when nutrients are deficient. In aggregate form, some individuals contribute to the formation of a stalk, on top of which sits a fruiting body full of spores that disseminate and germinate in the proper moist environment.

Habitats of Diverse Protists

At that place are over 100,000 described living species of protists. Most all protists exist in some blazon of aquatic surround, including freshwater and marine environments, damp soil, and even snow. Paramecia are a common case of aquatic protists. Due to their affluence and ease of use as research organisms, they are often subjects of written report in classrooms and laboratories. In addition to aquatic protists, several protist species are parasites that infect animals or plants and, therefore, live in their hosts. Amoebas can be human parasites and can cause dysentery while inhabiting the pocket-sized intestine. Other protist species alive on dead organisms or their wastes and contribute to their disuse. Approximately k species of slime mold thrive on bacteria and fungi within rotting trees and other plants in forests around the earth, contributing to the life cycle of these ecosystems.

Source: https://courses.lumenlearning.com/boundless-biology/chapter/characteristics-of-protists-2/

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