Phylum protozoa, Biology

PHYLUM  PROTOZOA

Definition  and  Introduction

 All  unicellular ( or  acellular )  eukaryotic  animals.

Most  primitive (Gr. Protos = first=zoon= animals ) organisms  considered  animals  because  of heterotrophic nutrition  and motility .Although the whole  body is a single  minute cell . it  performs all vital activities  that are  essential  for an   activities  that are  essential  for an  independent  existence  as a complete  organism. About  50,000 species   (30,000 present  and 20,000  extinct ) are  so far know, but  the total  number  of individual  protozoans  in nature  must  be much  more than the  of  the  membrane   of any  other phylum.

Brief History

Protozoans  were first studied  by Leeuwenhoek 1677. The  name  Protozoa was  coined by Goldfuss 1871. The  branch  of their  study is called  protozoology .

Important characters

1.      Usually minute (0.001-3.00mm)  microscopic,  free-living  in water , damp   soil,  or decaying  organic  matter, Many parasitic in other animals  and plants  .Some  symbiotic  or commensal.  Solitary or colonial. Free moving or sessile.

2.        Body  symmetrical  or asymmetrical. Shape  variable , oval, elongated ,  spherical,  or otherwise , but  fixed in most  species  unstable and  ever-changing  in  some.

3.      Body  naked with  only the  plasma membrane , or  covered by a thin pellicle . Some with  a hard , horny,  limy or siliceous  covering called shell, test  or lorica.

4.      Division of  labour  exhibited by specialized cell structures or organelles formed of macromolecules. Hence , only  molecular or protoplasmic level of body  organization ,

5.      One  to several  nuclei,  mostly similar when more  than one, but  of two  types  ( unclear dimorphism )  in some .

6.      Locomotory organelles  pseudopodia,  flagella , or cilia,

7.      Nutrition  principally  heterotrophic ( animals  like)  holozoic , saprozoic  saprophytic (absorbing  liquid  substances of  animal or plant  origin from the sur-roundings or parasitic. Some  are  autotrophic  or holophytic  ( plant like)  but usually , these can also  carry  some kind of heterotrophic  mutrition  (mixotrophic) ,Digestion in  holozoic  protozoans  occurs in food  vacuoles with  the help  of lysosomal enzymes.

8.      If  necessary  the quantity of water is regulated ( osmo  regulation )  by one  or  more contractile  vacuoles.

9.      Gaseous exchange and excretion  by diffusion through  body  surface . Ammonia  is principal  nitrogenous  waste (ammonotelic).

10.  Reproduction asexual  or sexual. Asexual  by fission  or budding , sexual by  gametes or conjugation.

11.  Encystment common  for reproduction , dispersal or survival  during  adverse environmental  conditions.

Posted Date: 10/4/2012 2:55:00 AM | Location : United States







Related Discussions:- Phylum protozoa, Assignment Help, Ask Question on Phylum protozoa, Get Answer, Expert's Help, Phylum protozoa Discussions

Write discussion on Phylum protozoa
Your posts are moderated
Related Questions
Define Decreased oxygen availability at high altitude (Hypobaric hypoxia)? The governing biophysical factor at high altitude is decrease in barometric pressure with increase in

Q. What is the difference between respiration by cutaneous respiration and diffusion? Does blood participate in cutaneous respiration? Cutaneous respiration is not as simple as

How do taenias obtain food and make gas exchange? Tapeworms have hooks and sucking structures on their heads (scolex) that fixate the parasite in the gut wall; these structures

What are cell movements? How are these movements created? Cell movements are movements done by cell structures, like the movements of cilia and flagella, the pseudopod movement

Q. How different are hemoglobin and oxyhemoglobin? Where is it expected to find a higher concentration of oxyhemoglobin, in peripheral tissues or in the lungs? Oxygen-bou

Explain Procedure for Sub-Culturing of a Culture Now carry out the exercise following the steps given herewith: 1. Sterilize the inoculating loop and needle by heating to re

Explain the Miracidium larva? Miracidium is the first stage larva that comes out from the fertilized egg. i) Miracidium is an oval, microscopic, flattened larva which appear

How does the contraceptive diaphragm work? What are the limitations of this contraceptive method? The contraceptive diaphragm is an artifact made of latex or plastic that when

Q. What is low - density lipoprotein receptor pathway? Ans. The increasing cellular free cholesterol generated regulates the activities of two enzymes that are of crucial

External factors - Factors Controlling Metamorphosis in Insects In few cases an external factor may be accountable for initiating moulting, as for instance in the blood su