Kingdom Protista: Introduction, Classification, Characteristics and Examples

 Kingdom Protista:

Protists

    Kingdom Protista is a special kingdom of organisms. It includes mostly eukaryotic aquatic organisms. These organisms have characteristics which cannot be fitted into any other kingdom. Their mode of nutrition, reproduction, lifestyles, and body forms are different from the other four kingdoms. There are four major groups of protists:

• The single-celled protozoa
• Unicellular and multicellular algae
• Slime molds
• Oomycetes

Protozoa: Animal-like Protist

• These are animal like protists.
• These are unicellular eukaryotic organisms. 
• These are free-living, symbionts or parasitic. 
• They ingest their food by endocytosis.
• They use cillia flagella or psudeopodia for locomotion.

Some common protozoa are:

1. Ameoba
2. Ciliates 
3. Zooflagellates
4. Apicomplexans
5. Actinopods
6. Foraminifera

 Amoeba:

Ameoba

• Ameoba are may be free-living or parasitic.
• They are unicellular organisms.
  
• They live in marine, freshwater and soil.
• They have no definite shape.
• Pseudopodia are finger-tips like special structure, which they use for locomotion.
• They eat dead organic particle through endocytosis.
• Their size ranging from few micrometer to over 20 cm in diameter. On the other hand giant ameoba can be up to 20 millimeter.
• Some examples of ameoba are Entamoeba, Amoeba prostus and Acanthamoeba. 

Ciliates:

• Ciliates are unicellular with definite but changable body shape.
• They live in aquatic environment.

• 

  Cilliates

  They are heterotrophs. They consume tiny microorganism by phagocytosis.
• Some cilites attached to rock and some are motile.
• Cillia are short hair-like structures, which they use for locomotion. They can move in every direction by these cilia.
  
• They have two nuclei.One is small diploid responsible for sexual process and other is large polyploid responsible for growth and metabolism.
• Some common examples of ciliates are Paramecium, Trichodina and Colpodea.

Zooflagellates:

• These are unicellular and some are colonial cellular organisms.
• They are heterotrphs. They consume nutrition by absobing organic matter.
• Some zooflagellates are free-living, some are symbionts or parasites.
• They move through whip-like structure called flagella. They possess flagella from single to many.
• They have only one central nucleus.
• They are also aquatic organisms.
• They have spherical or elongated body.
• Parasitic flagelletes cause dieases such as sleeping sickness.
• Some common examples are Trichonympha, Choanoflagelletes and Trypanosoma.

Apicomplexans:

• Apicmplexanes are unicellular parasitic organisms.
• They are obligate paracitemeans they they cannot live without their host.
•  They have no specific structure for locomotion..
• Their movement is through flexing. But mostly are non-motile. 
• They consume nutrients from their host. They have non-photosynthetic plastid called 
• They live a part of life in one host and one part of life in other host(For example plasmodium live in intestine of mosquito and when it bite to human Plasmodium is transfered).
• Some common examples are Plasmodium, Coccidia and Laeraniina.

Actinopods: 

• They are unicellular organisms.
• They have rod-like psuedopodia, which they use for locomotion.
• They produce shells or tests. This shell act as skeleton.
• These shells are made of calcium. Its decomposition produce lime.
• They consume algae or other little microscopic organisms fo nutrition.
• Some examples of actinopods are Actinosphaerium, Radiolarans and Actinophphrys sol.

Foraminifera

Foraminifera:

• They are unicellular organisms.
• They are most simple microscopic organisms.
• They are free-living and sometimes symbionts with algae.
  
• They also produce shells of silica or calcium.
• They consume small animal captured through psuedopodia.
• Example of Foraminifera are Ammonia tepida and Marginopora.

Algae: Plant-like Protist

• Algae are unicellular, colonial and multicellular eukaryotic protists.
• They are autotrophs. They are primary producer of aquatic food chain.
• Their body is called a thallus. They lake specific stem, leaves and roots. 
• There small root hair-like structure is called rhizoid.
• They have different type of pigments such as chlorophyll a, chlorophyll b and carotenes.

Some common groups of algae are

1. Euglenoid
2. Diatoms
3. dinoflagellates
4. Green algae
5. Brown algae
6. Red algae

Euglenoid:

• Euglenoid are unicellular  organisms.
• To classify euglenoid in animal or plant kingdom was very difficult for taxonomist.
• Euglenoid are related to zooflagellates, based on molecular data.
• But they have plant like characteristics.
• They are only photosynthetic in the presence of direct sunlight.
• They become heterotrophs in the darkness. 
• They ingest organic particles for nutrition.
• They have whip-like structure called flagella, use for locomotion.
• Some common examples are Euglena, Astasia and Phacus.

Diatoms:

• Diatoms are unicellular and colonial cellular algae.
• They are microscopic marine or freshwater organisms.
• There are large number of diatoms in aquatic ecosystem.
• They are very important in food chain because theyare primary producer.
• They move through water currents.
• Their cell wall produce shellsthat overlap on each other like a petri dish.
• These shell are made of silica.
• Some commmon examples are Cyclotella, Asterionella and Fragilaria.

Dinoflagellates:

• Dinoflagellates are unicellular but mostly uncommon colonial cellular protists.
• The common name of dinoflagellates is dinophytes.
• They have photosynthetic pigment chlrophyll a, chlorophyll b and carotenes.
• They also are important producer in aquatic food chain.
• They mostly have two flagella for locomotion.
• When they bloom it gives red or brown colour to water.
• Their cell wall is in the form of shells.
• Some common examples of dinoflagellates are Ceratium, Gonyaulax and Syndinials.

Green algae:

• Green algae is unicellular and colonial cellular protist.
• It is very common and well known protist found in moist and wet place.
• They have photosynthetic pigment chlorophyll a, chlorophyll b and carotenoids. 
• Green algae thought to be the firsr plant on earth.
• They have flagella for locomotion.
• Some common examples are Carophyte, Chlorella and Ulva.

Red algae:

• These unicellular or multicellular protists.
• They are called red algae because of phycobilins, a red pigment.
• Some red algae are macroscopic.
• Their rhizoids are attach to rock or soil in the water.
• They take part in building coral reefs.
• They are flattened sheet of cells.
• Some comon examples are Coral strands, Polysyphonia and Irish moss.

Brown algae:

• They also are macroscopic multicellular protist.
• They have a pigment fucoxanthin which give its greenish-brown coour.
• They are non-motile.
• They are giants of kingdom protists.
• The largest brown algae are kelps. Kelps are tough and leathery.
• Some common examples are Rocky weeds, Wakame and Ectocarpus. 

Fungus-like Protists:

• They are multicellular macroscopic protists.
• They are different from fungi for several characteristics.
• They have centriole.
• Their cell wall made of cellolose instead of chitin.
• They have some characteristic related to fungi.
• They contain hyphae.
• They are non-photosynthetic.