General characters of protozoa
■ Protozoa may be defined as microscopic and acellular animalcules, without tissues and organs, having one or more nuclei, but no nucleus ever in charge of a specialized part of cytoplasm.
■ They exist either single or in colonies which differ from metazoan in having all the individuals alike except when engaged in reproductive activities.
■ Small usually microscopic animalcules, ordinarily not visible without a microscope.
Simplest and most primitives of all animals, with protoplasmic grade of organization.
■ Body unicellular, containing one more nuclei which are monomorphic or dimorphic.
■ Solitary or forming loose colonies in which individuals remain alike and independent.
■ Body symmnetry is none, bilateral, radial or spherical.
■ Body naked or bounded by a pellicle and often provided with simple to elaborate shells or exoskeletons.
■ Body form usually constant, varied in some, while changing with environment or age in many.
■ The single cell body performs all the essential and vital activities, which characterize the animal body; hence only subcellular physiological division of labor.
■ Locomotor organclles are finger-like pseudopodia or whip-like flagella or hair like cilia or absent.
■ Nutrition holozoic (animal-like), holophytic (plant-like), saprozoic or parasitic. With or without definite oral and anal apertures.
Digestion occurs intracellularly inside food vacuoles.
■ Respiration and excretion through general surface or through contractile vacuoles, which serve mainly for osmoregulation.
Classification
This Phylum divide into 4 Sub-Phylum :
1 Sarcomastigophora
2 Sporozoa
3 Cnidospora
4 Ciliophora