Kingdom Protista – Animal like Protists or Protozoans

Kingdom Protista – Animal like Protists or Protozoans & its Characteristics

Kingdom Protista – Animal like Protists or Protozoans

· Animal like Protists or Protozoans are the organisms which are heterotrophs and live as predators or parasites.

· They are believed to be primitive relatives of animals, hence included in Kingdom Protista in Five Kingdom Classification.

· They are heterotrophic organism which are almost found in every habitat. Some of them also show symbiotic nutrition.

·  They are free living or exists as parasites in animals.

·  They are acellular and microscopic organisms.

·  Parasitic Protozoa produce some of the most deadly diseases. Such as Malaria etc.

Classification of Animal like Protists or Protozoa

· There are four major groups of protozoan, on the basis of their locomotory organs

1.      Flagellated Protozoans or Zooflagellates

2.      Ciliated Protozoans or Ciliates

3.      Amoeboid Protozoans or Sarcodina

4.      Parasitic Protozoans or Sporozoans


·  Most Primitive. They are acellular or non-cellular having protoplasmic level of organisation.

·  They possess one or more flagella for locomotion.

·  They may be free living or parasitic.

·  Zooflagellates are generally uninucleate, occasionally multinucleate.

·  The body is covered by a firm pellicle. They lack Cell Wall.

·  Nutrition is holozoic, saproboic and parasitic.

·  Asexual reproduction is by binary fission.

Examples –

·Trypanosome – The parasite of sleeping sickness. It was first observed by Forde in 1901. Fruce discovered that the parasite of sleeping sickness is transmitted by tse-tse fly.

· Leishmania – it causes Kala azar, a severe Liver infection.

· Trichonymph – Inhabitant of gut of Termites capable of Digesting Cellulose.


·  This group consists of Amoeba and their shelled relatives.

· Sarcodines are mostly free living, found in fresh water, sea water and on damp soil. Only a few are parasitic.

·  Nutrition is Holozoic.

· The cytoplasm is differentiated into outer layer of clear plasmagel called Ectoplasm and inner granular mass plasmasol known as Endoplasm.

·  The Various cell organelles floats in endoplasm such as Contractile Vacoules, Nucleus etc.

· They develop pseudopodia which are temporary protoplasmic outgrowths. They are of four types- lobopodia (broad and blunt), filppodia (slender, unsupported, and independent), axpodia (slender with axial support) and reticulopodia (slender, reticulate).

·  Pseudopodia are used for locomotion and engulfing food articles.

·  The body may be covered with plasmalemma or a shell.

·  Reproduce Asexually by Binary Fission.

Examples –

· Amoeba proteus – The Proteus Animalcule. Amoeba was discovered by Russel Von Rosenhoff in 1755.

· Entamoeba histolytica – Lamble (1859) discovered Entamoeba histolytica. It resides in the upper part of the human large intestine and causes the disease known as amoebic dysentery or amoebiasis.


·  All Sporozoans are endoparsites.

·  Uses spores to pass from one host to another.

·  Locomotory organelles (cilia, flagella, pseudopodia, etc.) are absent.

·  Nutrition is parasitic (absorptive).

·  The body is covered with an elastic pellicle or cuticle.

·  Contractile vacuoles are absent.

· Asexual reproduction occurs through syngamy followed by formation of haploid Spores called Sporozoids.

·  Complex Life cycle consisting of two distinct asexual and sexual phases. They may be passed in one (monogenetic) or two different hosts (digenetic).

Examples –

· Plasmodium – causative agent of Malaria.


·  Regarded as highly evolved Protozoans.

·  Ciliates are protozoan protists which develop a number of cilia during a part or whole of the life cycle.

·  Cilia are used for locomotion and driving food.

·  Most ciliates are free living individuals in fresh and marine waters. A few are parasitic.

·  There is a high degree of morphological and physiological specialization.

· They have micronucleus which is repository for Genetic information and macronucleus which contains multiple copies of Genetic material found in micronucleus.

·  The body is covered by a pellicle.

·  Nutrition is holozoic except in the parasitic forms.

· There are definite regions for ingestion and egestion. The region of ingestion consists of an oral groove, cytostome (mouth) and gullet.

·  They reproduce asexually by Binary Fission and Sexually by Conjugation.

Examples –

·  Paramecium– The slipper organism. Paramecium is a free living ciliate which is found in fresh water.


So, this was all about the Kingdom Protista – Animal like Protists or Protozoans and their Characteristics. In the next post (Click here), we will discuss about the Kingdom Fungi of Five Kingdom Classification by R.H. Whittaker in detail.

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