Characteristics of Kingdom Protista:
1. They are all eukaryotes and single-celled or unicellular organisms.
2. Members of this kingdom move by various means: e.g Amoeba uses Pseudopodia, Paramecium uses Cilia while Euglena uses Flagella.
3. They are microscopic organisms.
4. Mode of nutrition is variable: Autotrophic or Heterotrophic;
- Examples of heterotrophs are Amoeba and Paramecium.
- Examples of autotrophs are Euglena, Spirogyra, and Chlamydomonas.
5. They reproduce asexually by binary fission, multiple fission, spore formation, and budding.
6. They reproduce sexually by conjugation (a primitive form of sexual reproduction where individuals exchange genetic materials.)
- Examples are Amoeba, Paramecium, Euglena, etc.
7. Some cause serious diseases, such as malaria and amoebic dysentery
Organisms in this kingdom are called protists. They are similar to plants, animals, and fungi but do not have the same characteristics as them. They can be divided into plant-like protists, animal-like protists and fungus-like protists
Phylum Protophyta (Plant-like Protist):
Plant-like protists are known as Protophyta e.g. Algae such as Chlamydomonas, Spirogyra, Chlorella, Volvox, Pandorina, and Diatoms.
Characteristics of Phylum Protophyta:
i. Possession of chloroplast.
ii. Autotrophic nutrition.
iii. Store Carbohydrates in form of starch.
iv. Possess pyrenoid where starch is stored.
Phylum Protozoa (Animal-like Protists):
Animal-like protists are known as protozoa e.g. Amoeba, Paramecium, Trypanosoma, and Plasmodium.
Characteristics of Protozoa:
i. They feed on ready-made food.
ii. They have no cellulose cell walls.
iii. They have a plasma membrane called a pellicle.
iv. Freshwater protozoans have an organelle, the contractile vacuole, that collects and expels excess water.
v. They reproduce asexually by binary fission.
vi. They are mainly aquatic organisms while a few are parasitic.
vii. The organisms in this group move by different organelles e.g. Amoeba move by Pseudopodia, and Paramecium move by Cilia.
vii. All protozoans possess at least one nucleus, and many species are multinucleate. Paramecium has two kinds of nuclei: a large nucleus called a macronucleus and at least one small nucleus called a micronucleus.
ix. Protozoa can be divided into four phyla based on their locomotion: Mastigophora, Sarcodina (Rhizopoda), Ciliophora, and Sporozoa.
Classes of Protozoa based on Locomotory Organs:
The phylum protozoa may be divided into the following classes based on their locomotory organs
Mastigophora have one or two flagella for locomotion. e.g. Trypanosoma gambiense, Trichonympha sp.
Sarcodina (Rhizopoda) have pseudopodia (false feet) for movement and capturing food. e.g. Amoeba.
Ciliophora have cilia for locomotion and gathering of food. e.g. Paramecium.
Sporozoa are all parasitic and have no cilia or flagella. e.g. Plasmodium.
Phylum Amoebozoa (Fungus–like Protist):
Fungus-like protists are known as molds. They are heterotrophic feeders and absorb nutrients from decaying organic matter in their environment, similar to true fungi. The two major types of fungi-like protists are Myxomycota & Oomycota (slime & water molds.)
Euglena Viridis is a Protista and a typical example of an organism that shows both plant-like and animal-like features. It is a microscopic, unicellular and aquatic organism.
Animal-Like Characteristics of Euglena:
The characteristics of Euglena which makes it ‘animal-like’ include:
i. Possession of eye spot which enables it to detect light intensity.
ii. Possession of gullet for passage of food and food reservoir.
iii. It lacks a cell wall but possesses a pellicle, which is an animal-like feature, which makes its body flexible or gives the body a definite shape. Pellicles are made of protein.
iv. Possession of flagellum for movement.
v. Presence of myonemes which aids movement.
vi. In the absence of light, Nutrition is holozoic (a type of heterotrophic nutrition).
Plant-like Characteristics of Euglena:
The characteristics of Euglena which make it ‘plant-like’ include:
i. Possession of chloroplast which enables it to make its own food (photosynthesis.)
ii. Autotrophic mode of nutrition, if light is present.
iii. Stores carbohydrates s paramylum granules.
iv. Possess pyrenoids where starch is stored.