Protista | NEB Class 11 Biology

Faunal Diversity — Protista

General Characters of Phylum Protozoa

1. Unicellular and mostly microscopic
2. They may be free living found in fresh water, marine or live in damp soil. Some are parasites and few are saprophages and commensals.
3. Body is naked or covered with definite pellicle
4. Protoplasm is divisible in outer ectoplasm and inner endoplasm.
5. Respiration takes place by general body surface the process of diffusion.
6. Nutrition may be holozoic (animal like), holophytic (plant like), Saprophytic or parasite

Protozoa is classified in four classes on the basis of locomotory organs:

1) Rhizopoda / Sarcodina

• locomotory organelle is pseudopodia
• Body without definite pellicle
• free living or parasitic
• Nutrition holozoic or saprozoic
• Eg - Amoeba, Entamoeba

2) Ciliata

• Locomotory organelle is cilia
• Body with definite pellicle.
• One or more contractile vacuoles
• Eg - Paramecium, Vorticella

3) Flagellata

• Locomotory organelle is flagella
• Body with definite thin pellicle
• Nutrition autotrophic or heterotrophic or both
• Free living or parasite
• Eg - Euglena, Trypanosoma

4) Sporozoa

• Locomotory organelle is absent
• Exclusively endoparasites
• No definite contractile vacuoles
• Asexual reproduction by spores
• Eg - Plasmodium, Monocystis

Paramecium

• Kingdom - Protista
• Phylum - Protozoa
• Sub-phylum - Ciliophora
• Class - Ciliata
• Genus - Paramecium
• Species - caudatum

Habit and Habitat

• These are fresh water organisms which are found in lakes, rivers, streams, ponds etc. found in stagnant water, where organic matter is in plenty.

It feeds upon bacteria, small protozoa and other dead decaying in water with the help of oral cilia

Structure

Paramecium is a slipper like or slipper shaped animals due to having the cell as like that of sole of shoe or slipper. Body of paramecium is divisible into outer distinct part in cytoplasm called ectoplasm and inner granular parts called endoplasm. Body of paramecium is divisible in following parts:

1. Cilia: Ciliated longitudinal hair like structure called cilia. These are distributed equally throughout the pellicle except its posterior end. Cilia are of two types. Somatic cilia or body cilia help for body locomotion where as oral or buccal cilia help for feeding or collecting food materials
2. Pellicle: It is the thin elastic and layered membrane covering the cytoplasm of the body of paramecium.
3. Trichocyst: These are oval elongated and bag like structures which are arranged perpendicularly near the inner wall of pellicle.
4. Oral groove: It is a large depression located in ventro-lateral side of the body of paramecium.
5. Cytopyge: It is a temporary aperture for opening in the ventro-lateral side near the posterior end in the body of paramecium.
6. Nucleus: In paramecium there is nuclear dimorphism that is two types of nuclei a) Micronucleus and b) Macronucleus.

Micronucleus is a small, rounded and diploid structure situated in endoplasmic parts of paramecium. It helps for reproductions.

Macronucleus is generally larger, bean shaped and degenerating structure is the endoplasmic parts of paramecium. It helps to control metabolic activities.

Reproduction in paramecium

• In paramecium reproduction occurs both asexual and sexual method. The most common asexual reproduction in paramecium is called transverse binary fission and sexual method is called conjugation.

a) Transverse Binary fission

Binary fission is the process of asexual reproduction in paramecium, which occurs during favorable condition of temperature and availability of food materials.

Two contractile vacuoles and other necessary cytoplasmic part are formed on either side of the partition. Anterior part of a paramecium is called proter and posterior part is called opisthe. These two paramecia separate with each other from the partition and lead an independent life for next division.

Single binary fission completes at about 30-120 minute which depends upon temperature, food availability, population density etc. In 24 hours binary fission occurs at about 2-3 times to form 4-8 individual paramecium.

b) Sexual reproduction (Conjugation) in paramecium

• Conjugation is the process of sexual reproduction in paramecium. Paramecium of morphologically similar but physiologically dissimilar individual attached with each other from their lateral side to exchange their nuclear materials

1. Out of four haploid nuclei, three disappear in each conjugant.
2. The remaining nucleus divides unequally to form large stationary or female pronucleus and smaller migratory or male pronucleus.
3. The pronuclei in each conjugant unite to form a synkaryon (2n) or zygote nucleus.
4. After formation of zygote nucleus both conjugants separated with each other which are called ex-conjugants.
5. In this way eight Paramecia are formed after conjugation of each conjugant.

Significance of Conjugation

Conjugation helps for resources or regeneration of cytoplasmic parts of the body which makes the paramecium efficient for binary fission

• formation of two macronucleus is efficient for controlling the metabolic in the body of paramecium

Autogamy

It is a modified a form of self-fertilization. It was first reported in P. aurelia which is a bimicronucleus species. It occurs in single individuals.

• It is a sexual process which occurs without nuclear exchange. The process of cytogamy resembles that of conjugation in which the small Paramecia temporarily unite by their oral surfaces.

Malarial Parasite (Plasmodium vivax)

• Kingdom - Protista
• Phylum - Protozoa
• Class - Sporozoa
• Genus - Plasmodium
• Species - vivax

Habit and Habitat

It is cosmopolitan in distribution and mostly found in tropical and sub-tropical parts of the world.

• Plasmodium is a digenetic intracellular parasite.
• There are different species of Plasmodium, among them only four species are responsible for causing malaria fever in human and other vertebrates.

These species are as follows:

1. Plasmodium vivax
2. Plasmodium falciparum
3. Plasmodium malariae
4. Plasmodium ovale

Structure

a) Structure of Trophozoite

• A fully grown parasite is amoeboid and uninucleated called the trophozoite. Its body is covered with a plasma membrane. A distinct nucleus with nucleolus is found in the cytoplasm. Cytoplasm contains dark pigment granules. The endoplasmic reticulum formed of smooth or rough vesicles. The cytoplasm also contains food vacuoles having haemozoin.

b) Structure of Sporozoite

• Sporozoites are small (10-15 µm long), sickle shape, uninucleated and motile forms of parasite. Each sporozoite consists of pellicle, cytoplasm and nucleus. They are capable of wriggling movements.

Life cycle of Plasmodium vivax

Plasmodium vivax is a digenetic parasite which completes its life cycle in two different alternative host organism i.e., asexual cycle completes in human so, human is also called intermediate or secondary host organism and sexual cycle completes in female anopheles mosquito so, anopheles mosquito is also called primary or definitive host.

Asexual cycle in human (Schizogony)

1. Pre-erythrocytic phase
2. Exo-erythrocytic phase
3. Erythrocytic Phase / Schizogony

Pre-erythrocytic Phase

After the bite infected female anopheles mosquito numerous sporozoites first circulate through the blood about half an hour and enters into the liver cells to start its pre-erythrocytic cycle. After some times sporozoites in liver cell gain their nutrition grow in size and becomes a circular uninucleated structure called schizont. These cryptomerozoites again involve fresh liver cell to start its exo-erythrocytic phase.

Exo-erythrocytic phase

After liberating of numerous cryptomerozoites from the infected liver cell to the liver sinusoid, it again invade or enters the fresh liver cell to start its exo-erythrocytic phase. After entering into fresh liver cell these cryptomerozoites gain nutrition, grow in size and becomes a circular structure to form schizont stage as like that of pre-erythrocytic phase. Metacryptozoites are of two types i.e. small and numerous micro metacryptozoites which later on enter into RBC to start its erythrocytic phase and larger and less in number macro metacryptozoites which again enters into fresh liver cell to start its exo-erythrocytic phase.

Erythrocytic phase

Micro metacryptozoites enters into fresh RBC after releasing from the infected liver cells to continue its erythrocytic cycle. In RBC it forms a circular structure called trophozoite, which is excessive feeding stage. It feeds haemoglobin contained in RBC and develops a vacuole in the centre of the trophozoite and nuclear pushes towards the corner of the trophozoite to form ring like structure which is called signet ring stage. Among 12-24 merozoites some of them re-enter to the fresh RBC to continue its erythrocytic cycle and remaining merozoites form micro gametocytes and mega gametocytes.

Sexual cycle or Primary host of Plasmodium vivax in mosquito

Both gametocytes i.e. micro gametocytes with centrally located nucleus and macro gametocytes with eccentric nuclei enters into the body of female anopheles mosquito after seeking blood from infected human. Nucleus of microgametes divides into 6-8 nuclei, each nucleus develops a processed structure to form 6-8 flagellated microgametes is called exflagellation. Macrogametes develops a bulging structure called cone of reception through which microgametes is enters into macrogamete. Sporozoites wriggle towards the mouth of the stomach and enter into the body of healthy human along with saliva after the bite of infected female anopheles mosquito. Such process of formation of thousands of sporozoites inside the cysts wall of stomach as called sporogony.

Symptoms of Malaria fever

Malaria fever is the most infective parasitic diseases of human which kills many people in the world than that of other parasitic diseases except tuberculosis (T.B). There is no any infection in the body of mosquito but great damage in the body of human. There are two stage of malaria symptoms i.e.

1. Prodromal stage: It is the stage of mild headache, nausea, loss appetite, drying of mouth even during incubation period.
2. Paroxysm stage: It is the actual attack of malaria parasite which causes terrible chills and shivering, nausea, vomiting, drying of mouth and tongue becomes coated, are the other symptoms of malaria. This stage can be divided into three sub-stage i.e.
   1. Rigor Stage: Actual attack of malaria parasites
   2. Febrile Stage: High fever (temp. up to \(104^{\circ}\)F)
   3. Defervescence stage: Excess sweating and patients feels normal and healthy for certain period of time.

Due to excessive damage of RBC, patients suffer from anemia.

Treatment of Malaria fever

The drugs of choice against the malaria are quinine and chloroquine. Similarly daraprim, atabrin, plasmaquine and primaquine may be used.

Control measures of malaria parasite

1. Destruction of breeding places — Areas of swamps and stagnant water should be drained in order to reduce the number of breeding places of mosquitoes. If water sources are not possible to drain, Kerosene oil can be sprayed over the water surface.
2. Destruction of larvae and pupa — It is easier to kill them in their development by spraying of kerosene, paris green powder and DDT over the surface water
3. Biological control — Some fishes feeding on insects larvae and pupa like stickleback, anianous, Gambusia etc. may be introduced in the water reservoirs. They feed effectively on these development stages. So their another reduces number. Farming of ducks and cleaning of floating plants are also found effective to control mosquitoes.
4. Destruction of adult — Adult mosquitoes can be destroyed by burning sulphur, tar etc. Using DDT and other insecticides can also be effective way to destroy adult mosquito.