#imp #BIOLOGY #NCERT There are four major groups of protozoan | NCERT PCMB OFFICIAL ™✅

#imp #BIOLOGY #NCERT
There are four major groups of protozoans:-

1. Amoeboid Protozoans
These organisms live in freshwater, seawater or moist soil.

Examples Amoeba, Entamoeba, Radiolarians, Pelomyxa, Foraminiferans and Heliozoans.

General features of this group are following:-

(i) They move and capture their prey by putting out pseudopodia (false feet) as in Amoeba (as mouth is absent).

(ii) The body is without periplast. It may be naked or have a calcareous shell.

(iii) Flagella are present in some developmental stages. They also develop when food become scarce.

(iv) Nutrition is holozoic.
(v) Asexual reproduction occurs by binary fission, multiple fission, spores and budding and sexual reproduction occurs by syngamy.

2. Flagellated Protozoans
The members of this group are either free-living or parasitic. Examples Giardia, Trypanosoma, Leishmania, Trichonympha and Trichomonas.

General features of this group are following:-

(i) They have flagella for locomotion as their name suggests.

(ii) They may be aquatic, free-living, parasitic, commensals or symbiotic.

(iii) The body is enclosed by a firm pellicle.

(iv) Nutrition is holozoic, saprobic and parasitic.

(v) Asexual reproduction is by binary fission.

(vi) Sexual reproduction is observed in some forms only.
(vii) Various species of these protozoans causes diseases in humans. For examples,
* Trypanosoma (sleeping sickness)
* Leishmania (kala-azar, dum-dum fever)
* Giardia (giardiasis)
* Trichomonas (leucorrhoea).

3. Ciliated Protozoans
These are aquatic, actively moving organisms because of the presence of thousands of cilia.

Examples Paramecium, Opalina, Vorticella, Podophyra, Balantidium, etc.

Generalfeatures of this group are following :-

(i) Many ciliates live as free-living individual in fresh % and marine water (Paramecium).

(ii) A large number of cilia present on whole body surface.Cilia are used to capture food and for locomotion.

(iii) Nutrition is holozoic except in some parasitic forms.

(iv) The body is covered with flexible pellicle.

(v) There are definite regions for ingestion and egestion.

(vi) Ciliates have a larger macronucleus and smaller micronudeus.

(vii) They have small ejectable trichocysts for defense.

(viii) Osmoregulation occurs by contractile vacuoles.

(ix) Asexual reproduction occurs by transverse binary fission or budding. Cyst formation also occurs during unfavourable condition.

(x) Sexual reproduction by means of conjugation .