Kingdom Protista: Euglenoids, Slime Moulds & Protozoans Notes | Study Biology Class 11 - NEET

NEET: Kingdom Protista: Euglenoids, Slime Moulds & Protozoans Notes | Study Biology Class 11 - NEET

The document Kingdom Protista: Euglenoids, Slime Moulds & Protozoans Notes | Study Biology Class 11 - NEET is a part of the NEET Course Biology Class 11.
All you need of NEET at this link: NEET

Biological classification is an important topic for NEET aspirants and should be well understood to develop understanding and relation between different organisms and their characteristics. Let us take a glance at one of the important topics “Kingdom Protista” in this NCERT based notes.

Euglenoids

  • Euglenoids are Euglena-like unicellular flagellates that possess pellicle instead of cell walls which makes their body flexible.
  • They belong to the division Euglenophyta and class Euglenophyceae.
  • They were previously placed under class Phytomastigophora of Protozoa by zoologists.

EuglenaEuglena

Try yourself:Name the substance present in Euglenoids which makes their body flexible.
View Solution

Characteristic Features of Euglenoids

I. Habitat and Habits

  • Euglenoids occur in freshwater habitats in stagnant water and damp soils.

Freshwater habitat of EuglenaFreshwater habitat of Euglena

  • Euglenoids swim actively in a liquid medium with the help of their long flagellum. They can also perform creeping movements by expansion and contraction of their body. This phenomenon is called metaboly or euglenoid movements. 
  • Nutrition is holophytic (photoautotrophic), saprobic & holozoic.
    Kingdom Protista: Euglenoids, Slime Moulds & Protozoans Notes | Study Biology Class 11 - NEET
  • In dark, even photosynthetic forms can behave like heterotrophic, predating on smaller organisms (holozoic) or feeding on organic remains (saprobic). Such a mode of nutrition is called mixotrophic (e.g., holophytic + saprobic).
    Kingdom Protista: Euglenoids, Slime Moulds & Protozoans Notes | Study Biology Class 11 - NEET

II. Structure

Structure of EuglenaStructure of Euglena

  • Euglenoids are unicellular flagellate protists  without cell walls.
  • The body is covered by a thin and flexible pellicle (periplast).
  • The pellicle is composed of fibrous elastic protein, a small amount of lipid and carbohydrates and maintains a definite shape and also helps in temporary changes in the body shape.
  • The euglenoids have two flagella, usually one long and one short. 
  • The flagella bear hair (tinsels). So the flagella are tinsel type.
    Kingdom Protista: Euglenoids, Slime Moulds & Protozoans Notes | Study Biology Class 11 - NEET
  • Just in the area of the union of two roots, the flagellum bears a swelling called the paraflagellar body. 
  • An orange-red eyespot or stigma occurs attached to the membrane of the reservoir at the level of the paraflagellar body. Eyespot contains red pigment astaxanthin, found only in crustacea.
  • Both paraflagellar bodies and eyespots perceive the stimulus of light. They help in directing the organism toward the optimum light.
  • An osmoregulatory contractile vacuole occurs in the anterior part of the cell below the reservoir. It is fed by a number of canals. 
  • The contractile vacuole discharges its contents into the reservoir.
  • The photoautotrophs and holophytic forms possess chloroplasts with or without pyrenoids. Photosynthetic pigments include chlorophyll a and chlorophyll b.
  • A single large nucleus lies roughly in the middle. The nuclear envelope persists during division. The nucleolus also persists and divides into two.

III. Reserve Food

  • They store their carbohydrates as paramylon bodies.
    Euglena showing scattered Paramylon in the Cytoplasm
    Euglena showing scattered Paramylon in the Cytoplasm
  • The latter are formed outside the chloroplasts. 
  • Paramylon bodies are scattered throughout the cytoplasm. 
  • Paramylon is chemically different from starch and glycogen and does not stain with iodine.

Try yourself:In Euglenoids, the reserve food is
View Solution

IV. Reproduction

  • Euglena reproduces asexually by binary fission, they divide longitudinally. Sexual reproduction has not yet been definitely proved.

Longitudinal asexual reproduction in EuglenaLongitudinal asexual reproduction in Euglena

  • Examples: Euglena, Phacus, Eutreptia, Trachelomonas, Peranema

A. Euglena - The Spindle Organism 

Kingdom Protista: Euglenoids, Slime Moulds & Protozoans Notes | Study Biology Class 11 - NEET

  • Euglena is a large genus having 152 species (Gojdics, 1953). The common species is E. Viridis. It is found in freshwater ponds and pools. It also occurs on moist mud (Lackey, 1968). 
  • Euglena is a free-living solitary and unicellular flagellate.
  • Holozoic or phagotrophic forms are absent in Euglena. 
  • Asexual reproduction occurs by longitudinal binary fission.
  • Perennation occurs through cyst formation. 
  • The pellicle is made up of proteins (about 80%), carbohydrates and lipids. 
  • Besides swimming, Euglena can also perform creeping movements or metaboly.
  • The posterior end is pointed. The anterior end of the cell is blunt and bears an eccentric cytostome (mouth).
  • The cytostome leads into a tubular canal, also called the cytopharynx (gullet). 

  • The latter expands at the base to form a large rounded reservoir.

  • At one end of the reservoir, the cytoplasm contains an orange-red stigma (eyespot). 

  • The latter is photosensitive.

  • Just below the reservoir is found a contractile vacuole having many feeding canals (= accessory vacuoles). 

  • The contractile vacuole takes part in osmoregulation.

  • It expands and pumps its fluid contents in the reservoir. 

  • Chloroplasts are numerous, discoid shaped or ribbon-like. 

  • Pyrenoids (proteinaceous bodies) may be present in the chloroplasts.

  • Chlorophyll a and chlorophyll b are present.

  • The endoplasm contains several paramylon bodies.

  • They have polysaccharides called paramylon (β-1,3-glucan).
Euglena is studied as a plant as well as an animal. It is called plant-animal. 
Plant Characters of Euglena:

(i) Presence of chloroplasts with chlorophyll. 

(ii) Holophytic (photosynthetic) nutrition. 

Animal Characters of Euglena:

(i) Presence of pellicle which is made up of proteins and not of cellulose. 

(ii) Presence of stigma and paraflagellar body (photosensitive structures). 

(iii) Presence of contractile vacuole (not found in plants). 

(iv) Presence of longitudinal binary fission.

B. Consumer-Decomposer Protists - Slime Moulds 

  • Slime moulds possess the characteristics of both animals and fungi and, therefore, they are commonly called fungus-animals.  
    Slime Mould
    Slime Mould

Study deeply about Euglenoids and Slime moulds through this video:
Detailed Overview: Kingdom Protista

General Characters of Slime Moulds

  • The slime moulds live usually amongst decaying vegetation. They are quite common on lawns and moist fields.
  • They do not have chlorophyll.
  • They are surrounded by the plasma membrane only (somatic parts are without cell walls). However, the spores have cell walls made up of cellulose
  • At one stage of the life cycle, they have an amoeboid structure. 
  • They exhibit a wide range of colouration. 
  • They have phagotrophic or saprotrophic nutrition.
  • Both asexual and sexual modes of reproduction are found. They produce spores within sporangia. A spore possesses a cell wall of cellulose.
    Sporangia in Slime Moulds
    Sporangia in Slime Moulds
  • The slime moulds resemble both protozoa and true fungi. They are like protozoa in their amoeboid plasmodial stage and similar to true fungi in spore formation.
    Life Cycle of Slime Moulds
    Life Cycle of Slime Moulds

Try yourself:Which among the following are saprophytic protists?
View Solution

C. Protozoans

Protozoans are single-celled eukaryotes that can live either free or as parasites. They occur in a variety of sizes and shapes. They can be found in a range of habitats, including freshwater and marine. In nature, they are heterotrophic. They live as predators or parasites. Protozoa have a complicated internal structure and are microscopic.

Microscopic image of ProtozoaMicroscopic image of Protozoa

Try yourself:Which among the following comprises of animal like protists?
View Solution

Don’t want to read and yet learn the concept? Here’s an interesting video to learn the concepts in depth: Kingdom Protista: Protozoans


Classification of Protozoans

On the basis of locomotion, the protozoans are divided into four groups: 

Kingdom Protista: Euglenoids, Slime Moulds & Protozoans Notes | Study Biology Class 11 - NEET

Group 1. Flagellated Protozoans

  • They possess flagella for locomotion.
    Leishmania
    Leishmania
  • They may be free-living aquatics, parasites, commensals or symbionts
  • Zooflagellates are generally uninucleate, occasionally multinucleate.
    Structure of a Protozoa
    Structure of a Protozoa
  • The body is covered by a firm pellicle
  • Nutrition is holozoic, saprobic and parasitic
  • Asexual reproduction is by binary fission.
    Binary fission in Protozoa
    Binary fission in Protozoa
  • Sexual reproduction is recorded in some forms only. 

Examples: Trichonympha, Lophomonas, Giardia, Trypanosoma, Leishmania and Trichomonas. 


Some of the Protozoans are parasites present in human beings:

Trypanosoma gambiense

  • The parasite of sleeping sickness. 
  • The parasite of sleeping sickness is transmitted by tse-tse fly.
    Tse-Tse Fly
    Tse-Tse Fly
  • It causes Gambian sleeping sickness. 
  • Food is absorbed through the body's surface.
  • In human beings, the parasite lives in the blood plasma.
  • Later the parasite enters cerebrospinal fluid and damages the brain. 
  • It makes the patient lethargic and unconscious

Group 2. Amoeboid Protozoans

  • They develop pseudopodia which are temporary protoplasmic outgrowths.

AmoebaAmoeba

  • Pseudopodia are used for locomotion and engulfing food articles. 
  • Sarcodines (largest Phylum of Protozoans) are mostly free-living, found in freshwater, sea water and damp soil. Only a few are parasitic. 
  • The body may be covered with plasmalemma or a silica shell.
  • Nutrition is commonly holozoic
  • Asexual reproduction takes place by binary fission, multiple fission, budding and spores.
  • Sexual reproduction occurs through syngamy.
    Examples: Amoeba, Pelomyxa, Entamoeba, Radiolarians, Foraminiferans, Heliozoans.

Additional information on Amoeba and Entamoeba histolytica.

(a) Amoeba proteus: The Proteus Animalcule. 

  • It is found in freshwater.
  • Types of pseudopodia are lobopodia
  • A contractile vacuole is present for osmoregulation
  • Mitochondria are often seen aggregated around the contractile vacuole of the Amoeba
  • The cytoplasm is differentiated into endoplasm and ectoplasm
  • Endoplasm is further differentiated into plasma gel and plasmasol
  • The body is covered by plasmalemma.
    Amoeba proteus
    Amoeba proteus
  • Nutrition is holozoic
  • The process of obtaining food by Amoeba is called phagocytosis which is done in 5 steps:
    Kingdom Protista: Euglenoids, Slime Moulds & Protozoans Notes | Study Biology Class 11 - NEETKingdom Protista: Euglenoids, Slime Moulds & Protozoans Notes | Study Biology Class 11 - NEET
  • 1. Ingestion: When a food particle is near the Amoeba, it forms temporary finger-like projections called pseudopodia around the food particle and engulfs it. 

    2. Digestion: The food is digested in the food vacuole with the help of enzymes.

    3. Absorption: It is then absorbed in the cytoplasm of the Amoeba by diffusion.

    4. Assimilation: The absorbed food provides energy and a part of nutrition is used for growth.

    5. Egestion: The undigested and the waste food particles are thrown out.

  • Sol-gel theory of amoeboid movement was given by Hyman and supported by Pantin and Mast.

(b) Entamoeba histolytica

  • Lamble (1859) discovered Entamoeba histolytica. 
  • Losch (1875) discovered its pathogenic nature. 
  • The life cycle of Entamoeba histolytica is monogenetic (single host life cycle). 
  • It resides in the upper part of the human large intestine and repeatedly causes the disease known as amoebic dysentery or amoebiasis.
    E. histolytica feeding in human large intestine
    E. histolytica feeding in human large intestine
  • The symptoms of the disease are abdominal pain and motions with blood and mucus
  • The parasite is generally one pseudopodium.
  • The contractile vacuole is absent as there is no need for osmoregulation.
  • It feeds on red blood corpuscles by damaging the wall of the large intestine and reaching the blood capillaries. It produces ulcers. 
  • Multiplication is by binary fission. 
  • A mature cyst is called a tetra-nucleate cyst. It has four nuclei and two chromatoid bodies.
  • Tetranucleate cyst is the infective stage. 
  • It is important to note that only one young amoeba with four nuclei hatches out from a cyst of E.histolytica
  • However, a single cyst of E. histolytica produces eight amoebae. 
  • The most effective medicine for amoebiasis is Metragyl or Flagyl.

Group 3. Sporozoans

  • All sporozoans are endoparasites
  • Locomotory organelles (cilia, pseudopodia, etc.) are absent.
  • Nutrition is heterotrophic & Saprozoic. Phagotrophy is rare. 
  • The body is covered with an elastic pellicle or cuticle.
    Structure of Sporozoa 
    Structure of Sporozoa 
  • Contractile vacuoles are absent
  • Asexual reproduction occurs through fission
  • Sexual reproduction takes place through syngamy
  • Life cycle consists of two distinct asexual and sexual phases. They may be passed in one (monogenetic) or two different hosts (digenetic).
    Life cycle of Plasmodium
    Life cycle of Plasmodium
    Examples: Plasmodium, Monocystis. Eimeria. Monocytes

Group 4. Ciliated Protozoans

  • Kinety system is present in ciliates which comprise cilia, kinetosomes (basal bodies) and kinetodesma (bundle of fibrils).
    Paramecium with cilia all over its body
    Paramecium with cilia all over its body

Kingdom Protista: Euglenoids, Slime Moulds & Protozoans Notes | Study Biology Class 11 - NEET

  • Most ciliates are free-living individuals in fresh marine waters. A few are parasites. 
  • The body is covered by a pellicle
  • Nutrition is holozoic except in parasitic forms. 
  • There are definite regions for ingestion and egestion. The region of ingestion consists of an oral groove, cytostome (mouth) and gullet
  • They have contractile vacuoles for osmoregulation.
  • Asexual reproduction takes place by transverse binary fission or budding
  • Cyst formation occurs under unfavourable conditions. 
  • Sexual reproduction is by means of conjugation.
    Examples: Paramecium, Vorticella, Opalina, Balantidium.

(a) Paramecium- The Slipper Organism or Slipper Animalcule: 

  • Paramecium is a free-living ciliate that is found in freshwater.
    Structure of Paramecium
    Structure of Paramecium
  • The most widely distributed species are Paramecium caudatum and Paramecium aurelia
  • Nutrition is microphageal
  • Bacteria are its chief food. 
  • Paramecium is a surface feeder
  • Pellicle maintains the shape. 
  • The cilia of the extreme posterior end are longer and form a bunch called a caudal tuft
  • Feeding Apparatus consists of peristome (oral groove), vestibule, buccal cavity, cytostome (cell mouth) and cytopharynx.
  • The latter opens into the endoplasm
  • A temporary opening called cytopyge (cytoproct or cell anus), is present a little behind the cytostome. Undigested food is passed out through cytopyge. 
  • Paramecium caudatum contains a single large macronucleus and one small micronucleus
  • Paramecium aurelia has one macronucleus and two micronuclei. 
  • Paramecium contains two contractile vacuoles surrounded by 12 radial (feeding) canals. 
  • The contractile vacuoles and radial canals are for osmoregulation
  • The food vacuoles are meant for intracellular digestion.
  • Both asexual and sexual reproduction are found in Paramecium.
    Asexual & Sexual Reproduction in Paramecium
    Asexual & Sexual Reproduction in Paramecium
  • Asexual reproduction occurs through transverse binary fission
  • Various methods of sexual reproduction in Paramecium are:
    (i) Conjugation & Autogamy: It corresponds to self-fertilization.
    (ii) Endomixis it corresponds to parthenogenesis. 
    (iii) Cytogamy: It shows the characters of both conjugation and autogamy.
    (iv) Hemixis only the macronucleus takes part in hemixis. In hemixis, the macronucleus first breaks into a few irregular pieces; later some pieces reunite to form the macronucleus. 
  • The remaining pieces disintegrate in the endoplasm. Thus hemixis is called the "Purification Act".

In this document you have learnt the following:

  • Euglenoids swim actively in a liquid medium with the help of their long flagellum. They can also perform creeping movements by expansion and contraction of their body. This phenomenon is called metaboly or euglenoid movements.
  • The euglenoids have two flagella, usually one long and one short. Each flagellum arises from a basal granule (blepharoplast). The flagella bear hair (tinsels). So the flagella are tinsel type.
  • Euglena is studied as a plant as well as an animal.
  • consumer-Decomposer Protists - Slime Moulds 
  • Slime moulds possess the characteristics of both animals and fungi and, therefore, they are commonly called fungus-animals.
  • Protozoans are single-celled eukaryotes that can live either free or as parasites. They can be found in a range of habitats, including freshwater and marine. In nature, they are heterotrophic. They live as predators or parasites.
  • On the basis of locomotion, the protozoans are divided into four groups: Flagellated Protozoans, Amoeboid, Protozoans, Sporozoans, Ciliated Protozoans.

Now you can try answering the questions from Kingdom Protista asked in NEET:

Q.1. Pseudopodia help amoeboids in _______
(a) locomotion
(b) ingestion of food
(c) locomotion and ingestion of food
(d) performing metabolic reactions

Correct Answer is Option (c)
Pseudopodia help amoeboids in both locomotion and ingestion of food. Pseudopodia are temporary extensions in amoeba that help them to move to as well as intake food by surrounding it with temporary extensions.


Q.2. Amebiasis is caused due to _______
(a) Amoeba proteus
(b) Entamoeba histolytica
(c) Chaos carolinense
(d) Trypanosoma

Correct Answer is Option (b)
Entamoeba histolytica is a parasitic amoeba in humans which in turn causes Amoebiasis. Amoebiasis results in abdominal pain, diarrhoea, blood in stool, fever and loss of appetite.

Attempt this test to check your knowledge about Kingdom Protista:
Test: Kingdom Protista

The document Kingdom Protista: Euglenoids, Slime Moulds & Protozoans Notes | Study Biology Class 11 - NEET is a part of the NEET Course Biology Class 11.
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