What are the characteristics of protozoa ? Any 10 ?
Answers
Explanation:
Definition:
Protozoa are eukaryotic, unicellular microorganisms, which lack cell wall.
Characteristics of Protozoa:
The major distinguishing characteristics of protozoa are given below:
1. Habitat- Protozoa are found in the aquatic environment. They live in freshwater or oceans. Some are free-living and some are parasitic in plants and animals. Mostly they are aerobic but some are anaerobic and present in the rumen or human intestine.
2. Size and Shape- The size and shape of Protozoa vary greatly, from microbial (1µm) to large enough and can be seen by the naked eye. The shell of unicellular foraminifera can have a diameter of 20 cm.
They lack the rigid cell wall, so they are flexible and found in various shapes. Cells are enclosed in a thin plasma membrane. Some of the species have a hard shell on the outer surface. In some of the protozoans especially in ciliates, the cell is supported by Pellicle, which may be flexible or rigid and give organisms the definite shape and help in locomotion.
3. Cellular Structure- They are unicellular having a eukaryotic cell. The metabolic functions are performed by some specialised internal structures.
4 .They mostly have one membrane-bound nucleus in the cell .
5 .The nucleus has diffused appearance due to scattered chromatin, the vesicular nucleus contains a central body called endosome or nucleoli. Nucleoli of apicomplexans have DNA, whereas amoeboids lack DNA in their endosome
Ciliates have micronucleus and macronucleus
The plasma membrane encloses the cytoplasm and other locomotory projections like flagella, pseudopodia and cilia .
6.Some of the genera have a membranous envelope called pellicle, which gives a definite shape to the cell. In some of the protozoans, epibiotic bacteria attach to the pellicle by their fimbriae .
7 . The cytoplasm is differentiated into outer ectoplasm and inner endoplasm, ectoplasm is transparent and endoplasm contains cell organelles .
8.Some of the protozoa have cytostome for ingesting food. Food vacuoles are present, where ingested food comes. Ciliates have gullet, a body cavity which opens outside .
9. The central vacuole is present for osmoregulation, that removes excess water
Membrane-bound cell organelles, like mitochondria, Golgi bodies, lysosomes and other specialised structures are present.
10 .Nutrition- Protozoa are heterotrophic and have holozoic nutrition. They ingest their food by phagocytosis. Some of the protozoan groups have a specialised structure called cytostome for phagocytosis.
The major distinguishing characteristics of protozoa are given below:
1. They do not have a cell wall; some, however, possess a flexible layer, a pellicle, or a rigid shell of inorganic materials outside the cell membrane.
2. They have the ability during their entire life cycle or part of it to move by locomotor organelles or by a gliding mechanism.
3. They have a heterotrophic mode of nutrition, whereby the free-living forms ingest particulates, such as bacteria, yeast, and algae, while the parasitic forms derive nutrients from the body fluids of their hosts.
4. They reproduce primarily by asexual means, although in some groups sexual modes also occur.