Protozoa - Definition, Characteristics and Classification

Protozoa,Protozoa Definition,General Characteristics of Protozoa,Protozoa Characteristics,Classification of Protozoa,Types of Protozoa

Protozoa - Definition, Characteristics and Classification

Protozoa - Definition, Characteristics and Classification

Protozoa : It is one of the most important topic in biology section of any competitive exams. According to Loud Study Experts analysis on previous year question  paper, at least one question from this topic is asked in every competitive exams in India.

Under this post, we will cover the following topics :

  • Protozoa Definition
  • General Characteristics of Protozoa
  • Classification of Protozoa 

Protozoa Definition

Protozoa Definition

Protozoa Definition


Protozoa Definition : Protozoa is a unicellular eukaryotic organisms which have some similar characteristics of animals such as motility and heterotrophy as well as plants like lack of cell wall.

Unicellular organism refers to organism which has a single cell.

Eukaryotic organisms or Eukaryotes refers to an organism which posses a nucleus within cell membrane in their cells.

Motility refers to the ability of an organism to move independently using metabolic energy.

Heterotrophy or Heterotroph refers to an organism which cannot produce their own food. Heterotrophs are dependent on other organic sources such as animal matter or plants for their food.

Some common names of Protozoa are Protozoon or Protozoan. The word Protozoa is derived from two greek words namely Proto meaning first and Zoa meaning animals. The word Protozoa was given by zoologist George August Goldfuss in 1820.

Protozoa exist in nature in the form of either a living organism or a parasite. Protozoa belongs to protista kingdom.

General Characteristics of Protozoa

General Characteristics of Protozoa,Protozoa Characteristics

General Characteristics of Protozoa

General Characteristics of Protozoa or Protozoa Characteristics :
  1. Protozoa are unicellular microscopic organisms.
  2. Solitory and colonial.
  3. Body is covered by pellicle.
  4. The single cell body perform all the essential and vital activity. Hence it is also called acellular.
  5. Nutrition is holozoic, saprophytic or parasites.
  6. The digestion occurs intracellularly inside food vacuole.
  7. Reproduction is asexual by fussion and budding , and sexually by conjugation and syngamy.
  8. The life cycle often complicated with ulternation of asexual and sexual phase.
  9. Locomotary organ are finger like pseudopodia or flageella or hair like cilia.
  10. Body surface is used for respiration.
  11. About 50000 species are known.

Classification of Protozoa

Classification of Protozoa,types of protozoa

Classification of Protozoa

Classification of Protozoa or Types of Protozoa:

Protozoa is further classified into 4 subphylum :
  1. sarcomastigophora
  2. sporozoa
  3. cnidospora
  4. ciliophora
1. subphylum - sarcomastigophora

I. locomotion by flagella and pseudopodia.
II. nuclii are monomorphic.

subphylum sarcomastigophora is further divided into 3 superclass :

superclass 1 - sarcodina

A. body naked.
B. nutrition holozoic or sporozoic.
C. asexual reproduction by binary fission.

superclass sarcodina is divided into 3 classes :

class 1. rhizopodia - pseudopodia without internal axial filament which maintain shape. eg : amoeba and entamoeba
class 2. actinopodia - pseudopodia with internal axial filament. eg : actinophrys
class 3. pyroplasmia - small parasite of red blood cells of vertebrate. eg : babesia.

superclass 2 - flagellata or mastigophora

A. free living.
B. nutrition autotrophic or hetrotrophic.
C. locomotion by flagella.

superclass mastigophora is divided into 2 classes :

class 1. phytomastigophora - autotrophic nutrition, reserve food material starch paramylum or oil. eg : euglena, volvox etc.
class 2. zoomastigophora - glycogen is reserve food material, chloroplast absent, hetrotrophic nutrition. eg : trypnosoma, leismania.

superclass 3 - opalinata

A. body covered with cilia like flageella.
B. nuclii as parasite in frog.
C. nuclii two to many. eg. opalina.

2. subphylum - sporozoa

I. locomotary organ are absent.
II.animals are exclusively endoparasite.

subphylum sporozoa is further divided into 3 classes :

class 1. telospora - the spore are without capsule or filaments. eg : monocystis or plasmodium.
class 2. toxoplasmea - the spore formation are absent, asexual reproduction present. eg : toxoplasma.
class 3. haplosporia - the spore covering are present. eg : icthyoporidium

3. subphylum - cnidosporea

I. no locomotary organ present.

subphylum cnidosporea is further divided into 2 classes :

class 1. myxosporidia - mostly parasites of fishes, large spore develop from several nuclii. eg : myxidium

class 2. microsporidia - mostly parasites are arthopods, small spores develop from single nucleus. eg : nasema

4. subphylum - ciliophora

I. locomotary organ are cilia.

subphylum ciliophora is further divided into 1 class :

class 1. ciliates - cilia present throughout the life. eg : paramoecium, balantidium etc.

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