The Kingdom Protista includes mostly unicellular eukaryotes such as protistan algae, Slimemoulds and Protozoans.
On evolutionary point of view this kingdom acts as as a connecting link between prokaryotic monera and multicellular eukaryotic kingdom.(fungi, plant and animals)
Examples: Euglena, Paramecium, Gonyaulax,
Diatoms, Amoeba, Entamoeba
General Characters of Protozoa:
- Protoplasmic level of organization ; no organs or tissues.
- Their shape may be constant or variable(Amoeba).
Nutrition: Euglena like protists show a double life; auto trophic and heterotrophic.
Many of the protists are photosynthetic autotrophs found mainly in fresh water and oceans. They are called phytoplankton e.g. diatoms.
Structure: Mostly unicellular and posses typical cell organelles like nucleus, mitochondria, endoplasmic reticulum (ER), Golgi bodies and plastids.
Locomotion: Some of them have cilia or flagella with 9+2 internal microtubular structure.
Reproduction: Asexual Methods (Binary Fission, Multiple fission, budding and spore formation) and Sexual methods by fusion of gametes.
Life Cycles: Zygotic Meiosis and Gametic Meiosis
Classification of Protozoa : Major groups of Protista
1. Photosynthetic Protists
Examples: Dinoflagellates, Diatoms and Euglenoids
2. Slime moulds :
- Cellular ( Dictyostelium)
- Acellular (Physarella and Physarum)
- Zooflagellates (Trypanosoma, Leishmania, Trichomonas, Trichonympha)
- Amoebae (Amoeba, Entamoeba)
- Sarcodines (Radiolarians and Foraminiferans)
- Ciliates (Paramecium, Opalina, Vorticella)
Related Multiple Choice Questions: MCQ on Kingdom Protista