THE KINGDOM PROTISTA (PROTOCTISTA), NOTES

THE KINGDOM PROTISTA (PROTOCTISTA)

The Kingdom Protista consists of primarily aquatic eukaryotic organisms.

All protists are eukaryotic and have evolved from prokaryotes. The other eukaryotic kingdoms, Plantae, Fungi and Animalia evolved from protists in various ways.

The protists are unicellular, colonial or simple multicellular organisms.

All protists are eukaryotic.

Protists are three groups. Animal like protists (Protozoz), plant like protists (Algae) fungi like protists (slime molds and water molds).

All protozoans are unicellular. Most of them ingest their food by endocytosis.

Common Name Form Locomotion Examples
Zooflagellates Unicellular, some colonial One or more Flagella Trypanosoma, Euglena,
Amoebas Unicellular, no definite shape Pseudopods Amoeba, Entamoeba
Actinopods Unicellular Pseudopods Radiolarians
Foraminifera Unicellular Pseudopods Forams
Apicomplexans Unicellular None Plasmodium
Ciliates Unicellular Cilia Paramecium,

Vorticella, Stentor

 

The intestinal parasite, Entamoeba histolytica. It causes amoebic dysentery in humans.

Pseudopodia form cytoplasmic projections.

In amoebas reproduction is by binary fission or multiple fission.

During unfavourable conditions cysts are formed in Amoebas.

 

Zooflagellates may be free-living, symbionts or parasites.

Zooflagellates are mostly unicellular but a few colonial forms are also present.

Trichonymphas are complex, specialized flagellates with many (hundreds of) flagella which live as symbionts in the guts of termites and help in the digestion of dry wood.

Trypanosoma is a parasitic flagellate in human causing African sleeping sickness. It is transmitted by the bite of infected tsetse fly.

Choanoflagellates are sessile marine or freshwater flagellates. These are attached by a stalk and their single flagellum is surrounded by a delicate collar. They closely resemble the collar cells in sponges.

Ciliates are unicellular organisms with a flexible outer covering called a pellicle. It gives them a definite but changeable shape.

In Paramecium, the surface of the cell is covered with several thousand cilia.

Contractile vacuoles perform the function of water regulation in freshwater ciliates.

Ciliates differ from the other protozoans in having two kinds of nuclei. One or more small diploid micronuclei involved in sexual process and a large, polyploid macronucleus that controls cell metabolism and growth.

Most ciliates reproduce sexually by conjugation.

Apicomplexans are a large group of parasitic protozoans some of which cause serious diseases such as malaria in humans.

Apicomplexans have no specific structures for locomotion but move by flexing.

The saliva of female Anopheles mosquito contains a chemical that prevents the coagulation of the blood.

Chill, followed by high fever are the symptoms of malaria. These are due to toxic substances that are released and affect other organs of the body.

Algae are aquatic, eukaryotic photosynthetic thallophytes.

Algae carry out 50 to 60% of all the photosynthesis on the earth. (Most of the rest by

The sex organs in algae are unicellular (the sex organs in plants are multicellular).

No Phylum Common name Form Locomotion Pigments Examples
1 Euglenophyta Euglenoids Unicellular Two flagella one long one short Chl. a, Chl. b Carotenoids Englena
2 Phyrrophyta Dinoflagellates Unicellular Two flagella Chl. a, Chl. c Carotenes including Fucoxan-thin Gonyaulax, Ceratium
3 Chrysophyta Diatoms Usually unicellular Usually none Chl. a, Chl. c Carotenes including Fucoxan-thin Diatoma, Frequilaria

Pinnularia

4 Phaeophyta Brown algae Multicellular Two flagella on reproductive cells Chl. a, Chl. c Carotenes including Fucoxan-thin Fucus, Macrocystis
5 Rhodophyta Red algae Multicellular or unicellular None Chl. a, c carotenes

Phycoerythrin

Chondrus, Polysiphonia
6 Chlorophyta Green algae Unicellular, colonial, multicellular Most have flagella Chl. a, Chl. b, carotenes Chlorella, Ulva, Acetabularia

Spirogyra

 

On the basis of molecular data, Euglenoids are thought to be closely related to zooflagellates.

Chlorophyll a, b carotene and xanthophylls (carotenoids) presefti Lugienoids, green algae and Green land plants.

Some species of Euglenoids are always colourless and heterotropliic.

The cell wall of each diatom consists of two shells that overlap where they fit together like a petri dish. This cell wall is composed of Silicon.

The giants of protista are included in Brown algae (e.g., Kelps).

All brown algae are multicellular.

Brown algae range from a few centimeters to approximately 75 meters in length.

Green algae and green land plants have monophyletic lineage. This is indicated by RNA sequencing.

Most green algae possess cell walls with cellulose.

Green algae have pigments, energy reserve products, and ceil walls that are identical to those of plants.

Green algae and green land plants have starch as reserve food.

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