Characteristics, Examples of protozoan

Over 1M Answers AvailableCategory: BiologyCharacteristics, Examples of protozoan
Gen. Sulhazan Staff asked 7 months ago

I have a few questions regarding the phylu protozoa, please try and help out with some reasonable answers. 

  • what are the characteristics of protozoa
  • what are the three; 3 types of protozoa with examples/structure
  • What are the disease caused by protozoa?
  • Is a protozoa a bacteria?
  • What is the kingdom of protozoa
1 Answers
Gen. Sulhazan Staff answered 7 months ago


PROTOZOA are the simplest of all animals and constitute the first or  lowest phylum in the animal series. They are mostly microscopic in size and, hence, are not ordinarily seen except with the aid of a microscope. However, when millions of them are congregated together they form conspicuous masses; for example, flagellates of the genus Euglena may be so numerous at the surface of a freshwater pond as to color the water green, and other types of protozoa that may be cultivated in glass dishes in the laboratory may be so numerous as to give a cloudy appearance to the culture medium.
Single individuals of some of the larger protozoa, such as the ciliate
Paramcecium, can be seen with the naked eye if the proper background
is provided.
Two types of protozoa exist with respect to their habitats. One type live in fresh water, salt water, or in moist places and are known as free-living protozoa. The other type live in or upon the bodies of other animals or plants and are called parasitic protozoa.
One environmental condition is necessary for both types and that is the presence of sufficient moisture to prevent drying. Only the resistance spores or cysts of certain species of protozoa are able to withstand dessication.
Free-living protozoa are not distributed among bodies of water in a haphazard fashion but each species is more or less restricted to a definite type of habitat just as are higher animals. Some species live in fresh water; others, only in salt water; some live in contact with the bottom; others, float about suspended in the water; some are known to live only in line soil, and others, only in sphagnum swamps.
Free-living protozoa are to be found almost every where on the surface of the earth where moisture exists.
Parasitic protozoa are likewise rather definitely restricted in their habitats. Every higher animal that has been carefully studied has been found to harbor parasitic protozoa. Each species of
animal, as a rule, is parasitized by its own peculiar species of protozoa. For- example, twenty-five different species of protozoa are known to live in man. Most of these species appear to occur in monkeys also, but only a few of them have been recorded from other animals. The parasitic species are usually separated upto two groups; those that live in the digestive tract are known as intestinal protozoa and those that live principally in the blood, as blood-inhabiting protozoa.
The number of species of protozoa is very great and can hardly be estimated. Thousands of species of free-living protozoa have been described, and each species of higher animal seems to possess one or more species of protozoa peculiar to itself, hence the number of parasitic protozoa must be at least as great as that of all other animals combined. The number of individuals is likewise enormous. Billions of free-living species may exist in a single pond. Among parasitic species we need only refer to the millions of ciliates that occur in the stomach of cattle and the millions of flagellates that live in the cecum of almost every rat.
These immense numbers of protozoa are not difficult to separate into groups and ordinarily are placed in four classes according to the presence or absence of locomotor organs and the character ofthese when present.
The four classes are as follows:

  • CLASS I. SARCODINA. Type: Amoeba. Protozoa that move by means of pseudopodia
  • CLASS II. MASTIGOPHORA. Type: Euglena. Protozoa that move by means of flagella
  • CLASS III. SPOROZOA. Type: Monocystis. Protozoa without motile organs but with a spore stage in their life cycle.
  • CLASS IV. INFUSORIA. Type: Paramecium. Protozoa that move by means of cilia.