Protozoa, Majority of Cases, Diverse Group of Eukaryotic Protists, Mostly Unicellular, Cytoplasmic Threads, Embedded in Common Matrix, Leucophytes

Scholarships Dictionary Visa Details Study Abroad Exam Results Online Test Jobs

	Home
Eukarya Eukaryotic - Microorganisms Eukarya Eukaryotic-Microorganisms Introduction Protozoa Structure of Protozoan Protozoan Nutrition Classification of Protozoa Protozoa Classification System Human Diseases Caused by Protozoa Plant Diseases Caused by Protozoa Slime Moulds Acellular Slime Moulds / Plasmodial Slime Moulds Habitat Structure and Life Cycle Cellular Slime Moulds Habitat and Life Cycle Economic Importance of Slime Moulds

Home >> Microbiology >> Eukarya Eukaryotic-Microorganisms >>Protozoa

Your Ad Here	Protozoa Protozoa (Sing., protozoan; Gr. protos and zoan, meaning "first animal") include over 65000 species and their size, in majority of cases, ranges between 5 and 250 mm in diameter. Protozoa represent a diverse group of eukaryotic protists. They are mostly unicellular, but a few form colonies in which individual cells are joined by cytoplasmic threads or are embedded in a common matrix.
Thus colonies of protozoa are essentially aggregates of independent cells. The algal protists, on one hand, are far more plant-like but the protozoan protists, on the other hand, are far more animal-like. The latter are entirely without chlorophyll and their nutrition is accomplished variously by osmophilic heterotrophy, phagotrophy, and by symbiosis. Out of 65,000 described species of protozoa, slightly more than 50% are fossil forms; of the remaining 50%, some 22,000 are free-living species, while 10,000 species are parasitic.
It is estimated that even now there are hundreds of thousands of species yet to be described. Protozoa are distributed in diverse moist habitats. They commonly occur in sea, in fresh water, and in soil. Free-living protozoa have even been found in the polar region and at very high altitudes. Various protozoan species are parasitic and are found in association with many of the animals and plants. Parasitic protozoa have ability to modify their morphology and physiology to cope with a change in the host. For convenience, Plasmodium (the malarial parasite) produces male gametes in response to a drop in temperature when it is transferred from a worm-blooded mammalian host to a mosquito.	Your Ad Here
Although it is difficult to determine the detailed ancestry of protozoans, it is generally considered that they have conceivably evolved from leucophyte-type of algal ancestors. Leucophytes are those organisms that have lost their photosynthetic ability. Various algal protists belonging to dinoflagellates (also to some other algal groups) are known where the photosynthetic pigments have been lost and they possess phagotrophic mode of nutrition, e.g., Polykrikos. Noctiluca. Dinamoebidium. It is advocated that these leucophytes might have undergone modifications to give rise to nonphotosynthetic organisms. In this way, the leucophytes offer very valuable clues for tracing the protozoan ancestry.

	Home
Microfungi What is Mycology What is Moulds Vegetative Structure of Moulds Reproduction of Moulds Physiological Characteristics of Moulds Microbiologically Important Moulds Yeasts Vegetative Organization of yeasts Reproduction-of-yeasts Microbiologically Important Yeasts Fungal Plant Diseases Human and Animal Fungal Diseases Microalgae Algal Divisions Containing Microalgae Microbiologically Important Micro-Algae

Language >> English | Français | Español | Deutsch | Italiano | Portugues | Japanese | Korean | Sim-Chinese