Introduction to Kingdom Protista:
The Protists are first group of eukaryotic organisms. They are varied and don't possess much in common apart from the comparatively easy organization, as unicellular, or multicellular organisms that don't possess particular tissues or organs. It is this plain cellular organization which is main difference between protists and other eukaryotes in kingdoms Fungi, Plants and Animals.
Protists are discovered anywhere there is water. That can be fresh or marine water, snow, damp soils, and in bodies of other animals.
Protists can be unicellular, colonial, or multicellular. In colonial forms, all cells are related with similar, general functions, while in truly multicellular forms, "body" of organism is composed of the variety of cells, each cell kind with its own specialized function.
There are 3 groups of Protists they are,
i) The Protozoan Protists
ii) The Algal Protists
iii) The Fungal Protists
i) The Protozoan Protist:
These protists are animal-like, particularly in their nutrition. They ingest their food by phagocytosis. Few have mouth-like structures in which prey is put while others use pseudopodia to move and to engulf prey. Protozoans are further categorized into 4 divisions i.e.:
Rhizopoda: They are unicellular and possess pseudopodia like Amoeba proteus situated in fresh-water. Entamoeba hystolytica located in colon.
Amoeba proteus is the microscopic living organism that comprises of the single cell. Like most plant and animal cells, it possesses cell membrane, cytoplasm, nucleus and variety of inclusions in cytoplasm. It is about 0.3 mm across and lives in mud at bottom of fresh water ponds. Though it is just a single cell, it illustrates all necessary functions of any living organism.
These are all parasites and form small, infectious spores. All include complicated life cycles .Examples are species of Plasmodium like P. falciparium , P .malariae and P .vivax that is known to cause malaria.
Organisms are free-living, or symbiotic and parasites. Like Trypanosoma gambiense that causes African sleeping sickness and is spread by bite of tsetse fly.
The example of the organism in Division is Paramecium. These are lonely, fresh water organisms and utilize cilia to move. They have two nuclei, larger macronucleus and smaller micronucleus . Sexual reproduction is by conjugation
Paramecium is the ciliate protozoan. Paramecium, genus of protozoa of phylum Ciliophora, is frequently known slipper animalcules due to their slipper-like shape. Not like amoeba, paramecium has the distinct and permanent shape and definite areas of cytoplasm, (cell organelles), are specialized to perform particular functions.
Structure and Function:
Pellicle: the membrane covering which protects paramecium such as skin
Cilia: hair like appendages which help paramecium move food into oral groove
Oral Groove: gathers and directs food into cell mouth
Contractile Vacuole: contracts and forces additional water out of cell
Radiating Canals: paths to contractile vacuole
Cytoplasm: intercellular fluid required to hold vital cell parts
Trichocyst: utilized for defense
Gullet: forms food vacuoles
Food Vacuole: storage pocket for food
Macronucleus: larger nucleus that does normal cell functions
Micronucleus: smaller nucleus that is liable for cell division
ii) The Algal Protists:
These protists are photosynthetic; nutrition is plant-like. Roughly all have chlorophyll A, many of them have chlorophyll C, but only some have chlorophyll B. They also have the variety of carotenoids and other pigments, and often they are clustered into Divisions on the basis of similarities in pigments or color.
These are plentiful in plankton, infrequently happening in large numbers. They can occasionally turn out to be so many that water looks red, therefore this algal bloom is known as Red Tide.
The example of this is genus Euglena. It has flagella on frontal end, is utilized for movement. They have chloroplast for photosynthesis. If they are not in light, they can also get nutrition by phagocytosis. Euglena has light-sensitive "eyespot" or stigma near anterior ends.
Chlorophyta examples are Ulva, Clostridium, Volvox , Chlamydomonas, Spirogyra. These protists are also called as "green algae." Their chloroplasts and pigments within are similar to plants
Spirogyra is the filamentous alga. Its cells structure long, thin strands in huge numbers, contribute to recognizable green, slimy 'blanket weed' in ponds. Seen under microscope, every filament comprises of the wide chain of identical cells.
These organisms are normally called as "brown algae." They are multicellular and live in marine, temperate zone, coastal areas like Kelp, Fucus and/or Laminaria.
These are "red algae." They are multicellular and marine-dwelling, but are more usually discovered in tropical zones and deeper in ocean.
iii) The Fungus-like Protists:
Myxomycota: Also called as slime moulds.
Habitat: They are discovered on decaying wood, soil, lawns, forest, floors, fresh cow dung etc.
These organisms are known as "slime molds." They are fungus-like in the nutrition in that they take in nutrients from the environment.
Structure: Structure of slime mould is unusual in that nuclei undergo mitosis, but there is no cytokinesis. Rather, "body" is huge, multinucleate mass of cytoplasm. Slime molds are frequently brightly-colored (yellow or orange).
Slime molds are movable moving by amoeboid movement,
There are 3 groups of slime moulds which are
i) Plasmodial slime moulds exist as single cells with thousands of nuclei.
ii) Cellular slime moulds exist as separate single-celled amoeboid protists
iii) The slime nets
i) Formation of cysts in unfavorable conditions.
ii) Mucilage to stop desiccation.
iii) Few possess holdfast for anchorage.
iv) Few possess air bladders for buoyancy.
v) Thalloid body which offers little resistance to water flow.
The kingdom fungi:
It is fourth kingdom in six kingdom categorization of living things. Members of this kingdom don't have green pigment chlorophyll. Lack of chlorophyll dictates most of the characteristics. They are eukaryotes and great mainstream are multicellular except yeasts which are unicellular. They have extraordinary power to break up or dissolve roughly anything they attack by secretion of appropriate enzymes. Plant body, except unicellular forms, is usually composed of the interwoven mass of fine and delicate threads known as hyphae, collectively known as mycelium.
i) Fungi are eukaryotes.
ii) They are multi-cellular organisms apart from yeast that is unicellular (doesn't have hyphae). Main body of fungi is composed of hyphae that are long thin threads.
iii) All are heterotrophs and never have chloroplasts as such don't photosynthesise.
iv) Fungi feed saprotrophically absorbing soluble organic substances and inorganic from their surroundings. Several fungi feed on dead plants, animal faeces and bread.
v) They reproduce by spores at times asexual and at times sexual.
vi) Fungal cells possess cell walls which are composed of chitin.
Fungi are eukaryotic and possess membrane-bound cellular organelles and nuclei. They have no plastids of any type (and no chlorophyll). Hyphae of fungi are of 2 general types: Some are septate, and are separated by septa (walls) which divide cylindrical hypha into cells; in nonseptate fungi, hypha is one long tube. (Septa are perforated, though, allowing cytoplasm to flow throughout length of filament.) Mitosis happens in nonseptate hyphae, but there is no associated cytokinesis (division of cytoplasm) so hyphae are multinucleate (with many nuclei). Special name for the condition-organism or part of organism with several nuclei not divided by walls or membranes-is coenocytic, and organism is coenocyte. They possess rigid cell wall made up of chitin that may be layered with mannans, glucans and other polysaccharides in relation with polypeptides. Few lower fungi have cellulose in the cell wall Inner to cell wall is plasma membrane which is typical bi-layered membrane additionally to presence of sterols. The unique property of nuclear membrane is that it perseveres throughout metaphase of mitosis not like in plant and animal cells where it dissolves and reforms. The nucleus has paired chromosomes.
Fungi exist in 2 fundamental forms; filamentous (hyphal) and single celled budding forms (yeast). Every fungus possesses distinctive eukaryotic morphology.
Categorization in Kingdom Protista:
There are 4 phyla in kingdom fungi. They are:
1) Ascomycota they demonstrate characteristics given below:
i) They are single celled.
ii) The mycelium is septate
iii) Conidia structure is the common feature
iv) The ascus generally has eight ascospores which are formed endogenously
v) Sexual reproduction is decreased to fusion of 2 compatible nuclei
vi) Motile cells are not present
vii) The ascocarp is multicellular and complex bearing the asci
viii) It is open and cup- or saucer shaped (apothecium) oval or flask shaped with the small apical opening. (known as perithecium) or entirely closed (known as cleistotherium).
2) Deuteromycota: they demonstrate diagnostic features given below:
i) Myceluim is septate
ii) Sexual or perfect stage is unidentified
iii) Reproduce generally by means of conidia like fusarium
3) Zygomycota: they demonstrate diagnostic features given below
i) The mycelium is unseptate and coenocytic
ii) The sporangia possesses numerous sporangiospores
iii) Sexual reproduction is oogamous in Oomycetes and isogamous in zygomycetes.
iv) Biciliate motile cells are made by several species
v) The zygote is unicellular and simple like Mucor, Cystopus, Rhizopus
i) The mycelium is septate
ii) Conidiia formation is not general feature
iii) The basidium generally has four basiodiospores formed exogenously
iv) Sexual reproduction is decreased to fusion (karyogamy) of 2 compatible nuclei (+ ands-) in young basiduim
v) Motile cells absent
vi) Basidiocarp (fruiting body) is unicellular and complex. Bearing basidia - frequently open, at times closed.
Clamp connection is common like Ustilago, Puccinia, Agaricus
Adaptive features of Kingdom Protista:
Fungi develop best in damp habitats, are discovered wherever organic matter is there. They are the successful class of land organisms. They have many characteristics in body and reproduction which adapt them to terrestrial form of life.
a) Fast spreading Hyphae
b) Chitinous Wall: Chitin in the thickened hyphal wall is resistant to decompose than are cellulose and lignin located in plant cell wall.
c)Rhizoids: Rhizoids anchor fungus to substrate and digest and then absorb food.
d) No Flagellated cells: They do not have flagellated cells throughout the life.
e) Production of numerous spores
f) They make large number of small, non motile spores.
g) Thick protective conidia
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