In this article we will discuss about: 1. Definition of Protozoology 2. Morphology of Protozoology 3. Life Cycle.
Definition of Protozoology:
The science of the study of the protozoa is called Protozoology. The term protozoa has been derived from the two Greek words (protos—first, zoon-animal). Protozoans are the first group of organized but simplest animals in the animal kingdom. Modern Zoologists thought that the higher animals have been evolved from the single celled protozoans through the evolutionary processes.
Hence protozoans are the first group of animals that appear on this earth surface. So they are regarded as the most primitive animals in the animal kingdom. They are unicellular without any tissue grade of organization but multiply asexually by binary or multiple fission or by budding, in some cases sexual reproduction by conjugation.
Morphology of Protozoology:
They are very minute and microscopic animals. The structure of a protozoan “cell” consists of cytoplasm body and nucleus. The cytoplasm is differentiated into two parts— the outer hyaline portion, ectoplasm; function is locomotive, protective and sensory and the inner granular portion, the endoplasm, function is nutritive and reproductive.
Generally the protozoans possess definite locomotory organs, such as flagella, cilia or pseudopodia. In some of them cysts are formed during extreme condition. In protozoa free living, parasitic or symbiotic nature of animals are noticed. Contractile vacuole is present in many protozoans. Nutrition in protozoans generally takes place by holozoic process, but in some cases saprozoic or holophytic, even parasitic mode of nutrition also occur.
Life Cycle of Protozoology:
Protozoan can multiply by asexual method of reproduction for a long time. They may switch on to sexual method or undergoes cystic change to its host. In parasitic protozoa both asexual and sexual reproductions occur in a different host. This process is known as alternation of generation.
Amoebae, intestinal flagellates, Balantidium coli, etc. are monogenetic i.e. require one host to complete their life cycles. The parasites may adopt in a different host as well and transfer themselves passively in cystic stage. Again some parasitic protozoa like Leishmania, Trypanosoma and Plasmodia, etc. are digenetic i.e. require two hosts to complete their life cycles.
In Plasmodia infection (Malaria), man is the secondary or intermediate host but mosquito is the definitive or primary host. Tsetse fly is the intermediate host and man is the definitive host in Trypanosomiasis. In Leishmaniasis sand-fly is the intermediate host and man is the definitive host.