Introduction
Introduction to Kingdom Protista
When pond water is observed under a microscope, tiny organisms such as Euglena, Paramecium, Fuligo, and Plasmodium can be seen. These organisms belong to Kingdom Protista.
Kingdom Protista was proposed by Ernst Haeckel in 1866. Later, R. H. Whittaker in 1969 included Protista in his Five Kingdom Classification.
Protists occupy an intermediate position between Monera and higher eukaryotic kingdoms.
Definition
Definition of Kingdom Protista
Kingdom Protista consists of microscopic, unicellular, primitive eukaryotic organisms having a true nucleus and membrane-bound organelles.
Protists are the simplest eukaryotes. This line is frequently useful in short-answer questions.
Important Terms
Meaning of Important Terms
| Term | Meaning |
|---|---|
| Eukaryotic | Cells having a true nucleus enclosed by a nuclear membrane. |
| Unicellular | Organisms made up of only one cell. |
| Microscopic | Visible only under a microscope. |
| Primitive | Having simple body organization. |
| Protoplasmic organization | One living cell performs all life functions. |
Important
General Characteristics
Mostly aquatic
Found in ponds, lakes, rivers, and moist soil.
Unicellular
Mostly single-celled; some like Volvox form colonies.
Eukaryotic
Possess a true nucleus and membrane-bound organelles.
Locomotion
Movement by pseudopodia, cilia, or flagella.
Nutrition
Holophytic, holozoic, mixotrophic, parasitic, or saprozoic.
Reproduction
Both asexual and sexual reproduction may occur.
Habitat
Habitat of Protists
- Freshwater ponds, lakes, and rivers
- Moist soil and decaying organic matter
- Inside plants and animals as parasites
Nutrition
Modes of Nutrition
| Type | Description | Example |
|---|---|---|
| Holophytic | Prepare food by photosynthesis. | Euglena |
| Holozoic | Feeds on solid food particles. | Paramecium |
| Mixotrophic | Both autotrophic and heterotrophic nutrition. | Euglena |
| Parasitic | Obtains food from host. | Plasmodium |
| Saprozoic | Absorbs dissolved organic matter. | Some protists |
Classification
Classification of Kingdom Protista
Algal protists
Photosynthetic, chlorophyll-containing aquatic forms such as diatoms and golden algae.
Fungus-like protists
Grow on decaying matter and resemble fungi, such as Fuligo.
Protozoan protists
Animal-like heterotrophs such as Amoeba, Paramecium, and Plasmodium.
Diagrams
Important Protists
Amoeba
Moves using pseudopodia and feeds by phagocytosis.
Euglena
A mixotrophic organism showing plant-like and animal-like characters.
Paramecium
Moves with cilia and feeds through the oral groove.
Plasmodium
A parasitic protist responsible for malaria in humans.
Importance
Importance of Protista
Beneficial
- Important in aquatic ecosystems
- Produce oxygen through photosynthesis
- Food source for aquatic animals
- Help recycle organic matter
Harmful
- Some species cause diseases.
- Plasmodium causes malaria.
Plankton
Types of Plankton
Phytoplankton
Plant-like protists. Example: Diatoms.
Zooplankton
Animal-like protists. Example: Paramecium.
Revision
Quick Summary
- Protists are primitive eukaryotes.
- Most are unicellular and aquatic.
- They have a true nucleus and membrane-bound organelles.
- Digestion is intracellular.
- They show different modes of nutrition.
- Both asexual and sexual reproduction occur.
Compare Amoeba, Euglena, Paramecium, and Plasmodium by locomotion, nutrition, and importance.
Pay special attention to diatoms, slime moulds, protozoans, and disease-causing examples.
Resources
Download PDF Notes
FAQ
Frequently Asked Questions
Because they possess a true nucleus but have a simple unicellular body organization.
Because it shows both plant-like and animal-like characteristics.
Plasmodium causes malaria.
Practice