RBSE Solutions for Class 11 Biology Chapter 34 Amoeba

Rajasthan Board RBSE Class 11 Biology Chapter 34 Amoeba

RBSE Class 11 Biology Chapter 34 Multiple Choice Objective Questions

Question 1.
The term “Amoibe” means :
(a) Very minute animal
(b) Simplest animal
(c) Changeable animal
(d) Presence of Pseudopodia

Question 2.
Role of contractile vacuole in Amoeba :
(a) Nutrition
(b) Respiration
(c) Osmoregulation
(d) Reproduction

Question 3.
Medium of food vacuole in Amoeba :
(a) Always acidic
(b) Always alkaline
(c) First alkaline and than acidic
(d) First acidic and later on alkaline

Question 4.
Type of pseudopodia in Amoeba :
(a) Actopodia
(b) Reticulopodia
(c) Lobopodia
(d) Fillopodia

Question 5.
Excretory substance in Amoeba :
(a) Ammonia
(b) Urea
(c) Guanine
(d) Uric acid

Answers :
1. (c)
2. (c)
3. (d)
4. (c)
5. (a)

RBSE Class 11 Biology Chapter 34 Very Short Answer Questions

Question 1.
Amoeba belongs to which class?
Answer :
Rhizopoda

Question 2.
The posterior end of Amoeba is called as ?
Answer :
Uroid

Question 3.
Who propounded sol-gel-theory of locomotion in Amoeba?
Answer :
Hyman

Question 4.
Which structures release enzymes into the food vacuoles?
Answer :
Lysosomes

Question 5.
Give the names of excretory crystals in Amoeba.
Answer :
Biurates and Triurates

Question 6.
Where Amoeba is found?
Answer :
Stagnant fresh water

Question 7.
Name the mode of reproduction in Amoeba that takes place during favourable conditions.
Answer :
Binary fission

Question 8.
Which provides biconvex shape to the nucleus?
Answer :
Honey comp lattice

Question 9.
What is meaning of term “Proteus”?
Answer :
Changeable shape

Question 10.
What is the basis of division of sol and gel?
Answer :
Microfibrils of proteins

Question 11.
Concern to nutrition, Amoeba is?
Answer :
Omnivorous and Holozoic

Question 12.
Where food is digested in Amoeba?
Answer :
Inside the food vacuoles

Question 13.
What is the mode of respiration in Amoeba.
Answer :
Aerobic respiration

Question 14.
In what form, stored food is found in Amoeba.
Answer :
Glycogen and Fat

Question 15.
Taking in of solid food by Amoeba is called as?
Answer :
Phagocytosis

RBSE Class 11 Biology Chapter 34 Short Answer Questions

Question 1.
How the terms systole and diastole are related to Amoeba?
Answer :
Amoeba is a fresh water animal, hence water enters into the body constantly by endosmosis. Simultaneously. Amoeba constantly expels out the water with the help of contractile vacuole. It is called as osmoregulation.

Question 2.
Write the main functions of plasmalemma in Amoeba.
Answer :

• Being elastic facilitates locomotion.
• Being semipermeable allows endosmosis.

Question 3.
What is cryptomitosis?
Answer :
It is a type of mitosis. It is characterized by formation of a modified achromatic spindle and by absence of differentiated chromosomes.

Question 4.
What is encystment? How it benefits Amoeba?
Answer :
During unfavorable conditions, Amoeba develops a three-layered cyst. It is called encystment. It protects it during adverse conditions.

Question 5.
Give the phillotaxic responses of Amoeba.
Answer :
Positive response to Amoeba to external stimuli is called as phillotoxis. It gives positive response to food contact, dim to moderate light, gravity, water current, cathode etc.

Question 6.
What will be the effect on contractile vacuole, if Amoeba is place in marine water,
Answer :
The contractile vacuole will disappear soon.

Question 7.
Explain folding unfolding theory of locomotion in Amoeba.
Answer :
Molecular Folding and Unfolding Theory : It was propounded by Goldacre and Lorsch (1950) to explain sol-gel theory. The plasma gel consists of Unfolded protein molecules and the plasmasol has folded protein molecules (Microfilaments). The gelation involves unfolding of the micro filaments and solation involves folding of the microfilaments.

Question 8.
Differentiate sol and gel phases.
Answer :
The inner part of endoplasm is called as plasma sol which contains folded protein molecules. The outer part of endoplasm is called as plasmagel which contains unfolded protein molecules.

Question 9.
Write the features of class-sarcodina.
Answer :
Presence of blund pseudopodia and absence of pellicle.

Question 10.
Why the pseudopodia in amoeba are called as lobopodia?
Answer :
Pseudopodia in Amoeba are blunt, hence are called as Lobopodia.

Question 11.
Explain egestion in Amoeba.
Answer :
Removal of the undigested food is called as egestion. It is normally by exocytosis. Normally, egestion takes place at the posterior end through a temporary opening in the plasmalemma.

Question 12.
Why it is more correct to called amoeba as a cellular.
Answer :
Structurally, it is unicellular but its one cell performs all the vital activities. Hence, it is called a cellular.

Question 13.
What is assimilation?
Answer :
The digested food is absorbed by the surrounding cytoplasm. All the parts of the amoeba get the nutrients by the cyclic movement of the cytoplasm called the cyclosis. These nutrients are used to build new protoplasm.

Question 14.
Give an account of vacuoles found in Amoeba.
Answer :
The endoplasm of Amoeba consists of three types of vacuoles viz.
Contractile Vacuole : Amoeba has one contractile vacuole which is formed near the nucleus by the fusion of water droplets. It is bounded by a thin plasma membrane and surrounded by many mitochondria. After attaining a specific size, it moves towards the periphery and on contact with plasmalemma burst suddenly to release the water outside. The contractile vacuole performs osmoregulation. The formation of contractile vacuole is called as diastole which is a gradual process and bursting of contractile vacuole is called as systole which is a sudden process. The contractile vacuole also helps in respiration and excretion.

Question 15.
What is the role of food vacuole in Amoeba.
Answer :
Amoeba always exhibits intra cellular digestion that takes place inside the food vacuole with the help of lysosomal enzymes.

RBSE Class 11 Biology Chapter 34 Essay Type Questions

Question 1.
Describe ultra structure of Amoeba. Give labelled diagram.
Answer :
Amoeba is microscopic and a cellular or non-cellular. Structurally, it is unicellular but its one cell performs all the vital activities. Hence, it is called a cellular.

The size of Amoeba Proteus is 0.2 to 0.3 mm (200 to 300 μ). Other species may reach unto 0.5 μ.

The shape of amoeba is irregular as it is not covered by any rigid covering except plasma membrane. Hence, there is no definite anterior and posterior ends.

The amoeba is colorless, translucent and appear like jelly.

The amoeba is polypodial i.e. it forms one to many pseudopodia. The pseudopodia are blunt and are called as lobopodia. The largest pseudopodium is considered to be the anterior end & the opposite end is called as posterior or uroid end. The pseudopodia help in locomotion & ingestion of food.

The amoeba is covered by a plasma membrane (1 to μ thick) which is a selectively permeable membrane.

Internally, the amoeba consists of cytoplasm and nucleus. The cytoplasm is divisible into ectoplasm and endoplasm. The ectoplasm or ectosarc is the outer part which is transparent, homogeneous and without cell orgenelles. It is broadest at the anterior end of main pseudopodium which is called as hyaline cap. The endoplasm is inner substance which is transluscent, heterogenous and consist of all cell orgenelles. It is further divided into outer plasmagel and inner plasmasol (Mast. 1926).

Question 2.
What is food of Amoeba? Give an account of methods of ingestion’s in Amoeba.
Answer :
Nutrition :
Amoeba is omnivorous and holozoic. It’s food includes Bacteria, Diatoms, Algae, Dead organic material & other protozoans.

Ingestion :
Taking in of the food is called ingestion. It may occur at any place on the amoeba surface. Amoeba exhibits four methods of ingestion viz –

• Circumvallation : This method is used to ingest active food (motile food) with the help of pseudopodia. Their is formation of large food cup and food vacuole.
  
• Circumfluence : This method is used to ingest inactive or non-motile food with the help of pseudopodia. Comparatively small food cup and food vacuoles are formed.
  
• Import : In this method of ingestion, the food directly enters into the cytoplasm on contact with plasmalemma. It is also used to ingest food like algae. Later on. the food vacuole develops around the food.
  
• Invagination : In this method of ingestion, the plasma-lemma at the point of contact of food in pushes to form a tube inside the cytoplasm. The food enters through this food tube. A food vacuole develops at the inner end of the food tube.
  

Question 3.
What do you mean by Amoeboid locomotion. Explain sol-gel theory with the help of diagram.
Answer :
Locomotion :
Amoeba locomotes with help of pseudopodia which is called as Amoeboid Locomotion. The pseudopodia are cytoplasmic processes which can form at any place on the surface. One to many pseudopodia form at a time but it locomotes in the direction of main pseudopodium. Some inorganic ions such as Ca⁺⁺, Mg⁺ and K⁺ help in locomotion. Many theories have been put forth by different scientist to explain locomotion in Amoeba. Some of them are as follows :

• Adhesion Theory : It is not found to be correct, hence discarded.
• Rolling Movemen Theory : It was propounded by Jenning (1994). It is not found to be correct for Amoeba proteus. Hence, discarded.
• Contraction Theory : It was propounded by Schultze (1875) but not found to be correct.
• Surface Tension Theory : It was propounded by Berthold (1886). It is not found correct for Amoeba proteus.
• Walking Movement Theory : It was propounded by Dellinger (1906). It is not accepted for Amoeba proteus.
• Sol-Gel Theory : It was propounded by Hyman (1917). Later on, it as supported by Pantin (1923-26) and mast (1925) It is found to be correct. hence accepted universally.
  
  The sol-gel theory involves following steps ;
  (i) At the point of formation of pseudopodium, the plasma- gel converts into plasmasol and the plasmasol begins to flow. It is the beginning of pseudopodium formation.
  (ii) The constant flow of plasmasol results in the growth of the pseudopodium. When the plasmasol strikes the hyalin cap, it converts into plasmagel which is called as gelation.
  (iii) At the opposite end, the plasmagel converts into plasmasol to continue the supply of plasmasol. It is called as solation.
  
• Molecular Folding and Unfolding Theory : It was propounded by Goldacre and Lorsch (1950) to explain sol-gel theory. The plasmagel consists of Unfolded protein molecules and the plasmasol has folded protein molecules (Microfilaments). The gelation involves unfolding of the microfilaments and solation involves folding of the microfilaments.
  The folding & unfolding of the protein molecules take place at the cost of ATP.
• Fountain Zone Contraction Theory : It was propounded by Allen (1962). According to it, the region near the tip of the forming pseudopodium the everting plasmosol changes into plasmagel to form a wall or fountain zone. As a result, the anterior region develops tension.
  
• Hydraulic Pressure Theory : It was given by Rinaldi and Jahn (1963). According to it, at the posterior end the plasmagel contracts (Contractile protein fibres of Actin and Myosin) to create a hydraulic pressure on the plasmasol to flow anteriorly.

Question 4.
What is osmoregulation? Explain its process in Amoeba.
Answer :
Osmoregulation :
Amoeba is a fresh water animal, hence water enters into the body constantly by endosmosis. Simultaneously. Amoeba constantly expels out the water with the help of contractile vacuole. It is called as osmoregulation.

Initially, a small CV develops near the nucleus by the fusion of some water droplets and it grows gradually due to further fusion of these water droplets. This process is called as diastole. When the CV attains complete size, it moves towards outside and on contact with plasmalemma it bursts suddenly to release the water outside. It is called as systole

Question 5.
Describe modes of reproduction in Amoeba with the help of diagrams.
Answer :
Reproduction :
Amoeba primarily exhibit asexual reproduction. It exhibits following methods of reproduction.

Binary fission :
It is the most common method of reproduction that takes place during favorable conditions. In this method Amoeba divides by cryptomitosis (a type of mitosis) to form two equal size daughter amoebae. The binary fission takes about 30 minutes and it reoccurs at every 24 hours.

Before binary fission, Amoeba withdraws all pseudopodia and stops feeding. The contractile vacuole stops functioning temporarily. One daughter amoeba receives old CV and second daughter amoeba develops new CV.

Multiple fussion :
It is not a method of reproduction. It takes place during unfavorable conditions. The amoeba during unfavorable conditions develops a cyst wall which is three-layers. Inside the cyst, it repeatedly divide by mitosis to form 500 to 600 daughter nuclei. They get surrounded by little cytoplasm and develops a cell membrane. These structures are called as amoebullae. During favorable conditions, the cyst absorbs water, swells and bursts to release amoebulae. Each amoebula forms one young amoeba.

Sporulation :
According to Taylor (Scientist), Amoeba exhibits sporulation during unfavorable conditions. In this method, the nuclear membrane bursts to release chromatin granules in the cytoplasm. These chromatin granules form 200 to 300 groups of 2 to 3 granules. This condition is called as polyenergid nucleus. Every group get arranged with little cytoplasm and develops a cell membrane and later spore sheath. The resulting structure are called as pseudopodiospores. Finally, the parent amoeba degenerates to release pseudo-podiospores. During favorable conditions, every pseudopodiospore forms a young amoeba.

Regeneration :
It is not a method of reproduction. Amoeba has extreme power of regeneration. A small part of amoeba, if it contains a piece of nucleus, can regenerate to form complete amoeba.

RBSE Solutions for Class 11 Biology