Kingdom: Protoctista or Protista (unicellular Eukaryotes)

Protista includes unicellular eukaryotes. Algae, Diatoms and protozoan like amoeba, paramecium and euglena are few members of kingdom Protista. The term Protista was first used by Ernst Haeckel in 1886.Protista has mitochondria for cellular respiration and some have chloroplasts for photosynthesis. Protista exhibit both autotrophic and heterotrophic mode of nutrition. Some protista have appendages for locomotion such as hair-like cilia, whip-like flagella. They have an asexual mode of reproduction like binary fission and spore formation also have sexual reproduction.

Classification of Protoctista or Protista

Image showing classification of Protista.

Image Shoiwng Classification of Protista.

Image showing classification of Protista.

Some examples of Protista:

  1. Amoeba: unicellular, heterotrophs and found in freshwater and in soil. It grows and wraps pseudopods around food forming a food vacuole. Reproduce by binary fission (asexual reproduction is absent).

    Image showing structure of Amoeba.

    Image Showing Structure of Amoeba.

    Image showing structure of Amoeba.

  2. Entamoeba: Entamoeba is a genus of amoeboid protozoa that live in the human intestine. Some species of this genus are harmless, while others are pathogenic. E. histolytica is parasitic cause of death, after malaria. E. histolytica are transmitted through food and water and by fly and cockroach droppings.

  3. Plasmodium (The malarial parasite): Plasmodium is causative organisms of Malaria which infects red blood cells in mammals (including humans), birds and reptiles. Male Anopheles cannot cause malaria as it feeds on plant juices and not human blood.

    Image showing life cycle of Plasmodium in mosquito and man.

    Image Showing Life Cycle of Plasmodium in Mosquito and Man.

    Image showing life cycle of Plasmodium in mosquito and man.

  4. Euglena: Euglena is single-celled organisms that live mostly in fresh water and chloroplast contains green coloured chlorophyll for photosynthesis. Binary fission types of reproduction.

  5. The Diatoms: found in fresh water, unicellular, colonial or filamentous and cells are eukaryotic. They may be oval, spherical, triangular, boat-shaped etc. Sexual reproduction takes place by isogamy and oogamy.

    Image showing Euglena.

    Image Showing Euglena.

    Image showing Euglena.

    Image showing Diatoms.

    Image Shoiwng Diatoms.

    Image showing Diatoms.

  6. Other algae: Algae can be unicellular e.g. Chlamydomonas or multi-cellular like Spirogyra. Cell contains plastids and pigments like chlorophyll, carotenoids and phycobilins, reserve food mostly in starch and oils. Majority of algae are in aquatic habitat like freshwater or marine and others are terrestrial also.

    Image showing unicellular algae Chlamydomonas.

    Image Showing Chlamydomonas.

    Image showing unicellular algae Chlamydomonas.

    Image showing mutlicellular algae Spirogyra.

    Image Showing Spirogyra.

    Image showing mutlicellular algae Spirogyra.

Usefulness of Algae:

  • Algae are major sources of fuel (biodiesel and bioethanol) and food supplement.

  • Algae are used in Wastewater Treatment facilities and also as fertilizers.

  • Rich sources of vitamins A and E.

  • Blue green algae increase the soil fertility by fixing atmospheric nitrogen, e g., Anabaena, Aulosira, Spirulina, Nostoc etc.

  • Algae are useful natural resource of many commercial products.

  • Diatomite is used in the preparation of explosives, cement, bleaching powder, cosmetics, chocolates, metal polish, automobile polish and shoe polish.

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