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

Zooflagellates

·  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.

Sarcodina

·  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.

Sporozoans

·  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.

Ciliates

·  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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