ICAR JRF Plant Science Practice Series Memory Based 2023 Shift 1st  (Module 1) (41 – 80 MCQ) 

 

Objective Question 41

Which one of the following is Fungi Like Organism known to cause plant disease epidemics?

1. Saprolegnia
2. Phytophthora
3. Magnaporthe
4. Puccinia

A1: 1
A2: 2
A3: 3
A4: 4
Answer: A2: 2

Explanation: Phytophthora is an oomycete (fungi-like organism) responsible for major epidemics like late blight of potato. Others like Magnaporthe and Puccinia are true fungi.

 

Objective Question 42

Which one of the following is a fungus-like organism (Oomycete) known to cause plant diseases?

1. Magnaporthe
2. Phytophthora
3. Pythium
4. Puccinia

A1: 1
A2: 2
A3: 3
A4: 4
Answer: A2: 2

Explanation: Among the given options, Phytophthora belongs to oomycetes (fungus-like organisms), which are distinct from true fungi and are known for causing serious plant diseases such as late blight.

• Magnaporthe and Puccinia are true fungi
• Pythium is also an oomycete, but Phytophthora is the most well-known plant pathogenic example in this context.
• while Magnaporthe and Puccinia are true fungi. Pythium is also an oomycete, but the correct answer provided is Phytophthora.

 

 

Objective Question 43

Gene for Gene Interaction is best observed in

1. Biotrophic Pathogens-Host Pathosystem
2. Hemibiotrophic Pathogens-Host Pathosystem
3. Necrotrophic Pathogens-Host Pathosystem
4. Saprophytes

A1: 1
A2: 2
A3: 3
A4: 4

Answer: A1: 1

Explanation: Gene-for-gene interaction (Flor’s hypothesis) is typically observed in biotrophic pathogen-host systems, where specific resistance (R) genes in host interact with avirulence (Avr) genes of pathogen.

 

Objective Question 44

Which one of the following are biotrophic fungi?
(A) Albugo
(B) Puccinia
(C) Glomus
(D) Blumeria

1. (A), (B) and (D) only
2. (A), (B) and (C) only
3. (B), (C) and (D) only
4. (A), (B), (C) and (D)

A1: 1
A2: 2
A3: 3
A4: 4

Answer: A1: 1

Explanation: Biotrophs require living host tissue. Albugo, Puccinia, and Blumeria are obligate biotrophs, whereas Glomus is a mycorrhizal fungus (symbiotic, not pathogenic biotroph).

 

 

Objective Question 45

Polycyclic diseases are characterized by
(A) Air borne nature
(B) Foliar infection
(C) Multiplicity of infection
(D) Short generation time
Choose the correct answer from the options given below:

1. (A), (B) and (D) only
2. (A), (B) and (C) only
3. (A), (B), (C) and (D)
4. (B), (C) and (D) only

A1: 1
A2: 2
A3: 3
A4: 4

Answer: A3: 3

Explanation: Polycyclic diseases have multiple infection cycles in one season, are often airborne, affect foliar parts, and have short generation time, leading to rapid epidemic development.

 

 

Objective Question 46

Evolutionarily linked Genome Reduction is observed in
(A) Xylella
(B) Phytoplasma
(C) Phytophthora
(D) Magnaporthe
Choose the correct answer from the options given below:

1. (A) and (B) only
2. (A), (B) and (D) only
3. (A), (B), (C) and (D)
4. (B), (C) and (D) only

A1: 1
A2: 2
A3: 3
A4: 4

Answer: A1: 1

Explanation: Genome reduction is common in obligate parasites like Xylella and Phytoplasma, which rely on host metabolism. Phytophthora and Magnaporthe have relatively larger genomes.

 

 

Objective Question 47

Match List-I with List-II
List-I (Theory proposed/Characteristic) List-II (Author/Thinker)
(A) Gene for Gene (I) H.H. Flor
(B) Germ Theory (II) Anton de Bary
(C) Puccinia path (III) K.C. Mehta
(D) Elicitor (IV) Noel T Keen

1. (A)-(I), (B)-(II), (C)-(III), (D)-(IV)
2. (A)-(I), (B)-(III), (C)-(II), (D)-(IV)
3. (A)-(I), (B)-(II), (C)-(IV), (D)-(III)
4. (A)-(III), (B)-(IV), (C)-(I), (D)-(II)

A1: 1
A2: 2
A3: 3
A4: 4

Answer: A1: 1

Explanation:

• Gene-for-gene theory → H.H. Flor
• Germ theory in plant pathology → Anton de Bary
• Puccinia life cycle studies → K.C. Mehta
• Elicitors concept → Noel T. Keen

 

 

Objective Question 48

Given below are two statements, one is labelled as Assertion (A) and other one labelled as Reason (R).
Assertion (A): Oomycetes pathogens need high moisture for their dissemination.
Reason (R): Oomycetes pathogens do produce motile spores during their life cycle.
In light of the above statements, choose the correct answer from the options given below:

1. Both (A) and (R) are true and (R) is the correct explanation of (A)
2. Both (A) and (R) are true but (R) is NOT the correct explanation of (A)
3. (A) is true but (R) is false
4. (A) is false but (R) is true

A1: 1
A2: 2
A3: 3
A4: 4

Answer: A1: 1

Explanation: Oomycetes (e.g., Phytophthora, Pythium) produce motile zoospores with flagella that require free water for movement and infection. Therefore, high moisture is essential for their dissemination. Hence, both statements are true and the reason correctly explains the assertion.

 

 

Objective Question 49

Given below are two statements, one is labelled as Assertion (A) and other one labelled as Reason (R).
Assertion (A): Bacterial phytopathogen do cause explosive epidemics.
Reason (R): Bacterial phytopathogens have short generation time by binary fission.
In light of the above statements, choose the correct answer from the options given below:

1. Both (A) and (R) are true and (R) is the correct explanation of (A)
2. Both (A) and (R) are true but (R) is NOT the correct explanation of (A)
3. (A) is true but (R) is false
4. (A) is false but (R) is true

A1: 1
A2: 2
A3: 3
A4: 4

Answer: A1: 1

Explanation: Bacterial pathogens multiply rapidly through binary fission, often doubling in a very short time. This leads to rapid population buildup, causing sudden and severe (explosive) epidemics under favorable conditions. Thus, the reason correctly explains the assertion.

 

 

Objective Question 50

Given below are two statements, one is labelled as Assertion (A) and other one labelled as Reason (R).
Assertion (A): Only vegetatively propagated planting are responsible for transboundary movement of pathogens.
Reason (R): High moisture contents in the vegetative propagation material supports pathogen viability.
In light of the above statements, choose the correct answer from the options given below:

1. Both (A) and (R) are true and (R) is the correct explanation of (A)
2. Both (A) and (R) are true but (R) is NOT the correct explanation of (A)
3. (A) is true but (R) is false
4. (A) is false but (R) is true

A1: 1
A2: 2
A3: 3
A4: 4

Answer: A4: 4 

Explanation: Assertion is false because pathogens can spread through seeds, soil, planting materials, tools, and even vectors, not only vegetative propagules. Reason is true since vegetative materials (like tubers, cuttings) retain high moisture, which supports pathogen survival, but they are not the only source of spread.

 

 

Objective Question 51

Given below are two statements:
Statement (I): Uredospores are motile.
Statement (II): Viruses are motile.
In light of the above statements, choose the most appropriate answer from the options given below:

1. Both Statement (I) and Statement (II) are correct
2. Both Statement (I) and Statement (II) are incorrect
3. Statement (I) is correct but Statement (II) is incorrect
4. Statement (I) is incorrect but Statement (II) is correct

A1: 1
A2: 2
A3: 3
A4: 4

Answer: A2: 2

Explanation: Uredospores (rust fungi) are non-motile and dispersed by wind, not by active movement. Viruses are also non-motile particles and depend on vectors (like insects) or mechanical means for transmission. Hence, both statements are incorrect.

 

Objective Question 52

Given below are two statements, one is labelled as Assertion (A) and other one labelled as Reason (R).
Assertion (A): Mutation is a source of new genetic variation in populations.
Reason (R): Mutation leads to permanent changes in the DNA sequence which can be inherited.

In light of the above statements, choose the correct answer from the options given below:

1. Both (A) and (R) are true and (R) is the correct explanation of (A)
2. Both (A) and (R) are true but (R) is NOT the correct explanation of (A)
3. (A) is true but (R) is false
4. (A) is false but (R) is true

A1: 1
A2: 2
A3: 3
A4: 4
Answer: A1: 1

Explanation: Mutations introduce new alleles into a population, increasing genetic diversity. Since mutations involve heritable changes in DNA, the reason correctly explains the assertion.

 

 

Objective Question 53

Which of the following is primarily responsible for translocation of organic food in plants?

1. Xylem
2. Phloem
3. Cambium
4. Cortex

A1: 1
A2: 2
A3: 3
A4: 4

Answer: A2: 2

Explanation: Phloem transports sugars (photosynthates) from source (leaves) to sink (roots, fruits). Xylem transports water and minerals.

 

 

Objective Question 54

Given below are two statements:
Statement (I): Enzymes act as biological catalysts and speed up biochemical reactions.
Statement (II): Enzymes are consumed permanently during the reactions they catalyze.

In light of the above statements, choose the most appropriate answer:

1. Both Statement (I) and Statement (II) are true
2. Both Statement (I) and Statement (II) are false
3. Statement (I) is true but Statement (II) is false
4. Statement (I) is false but Statement (II) is true

A1: 1
A2: 2
A3: 3
A4: 4

Answer: A3: 3

Explanation: Enzymes are biological catalysts (true), but they are not consumed in reactions—they can be reused.

 

 

Objective Question 55

Which of the following is an example of a micronutrient required for plant growth?

1. Nitrogen
2. Phosphorus
3. Potassium
4. Zinc

A1: 1
A2: 2
A3: 3
A4: 4

Answer: A4: 4

Explanation: Zinc is a micronutrient, required in small amounts. Nitrogen, phosphorus, and potassium are macronutrients.

 

 

Objective Question 56

Given below are two statements, one is labelled as Assertion (A) and other one labelled as Reason (R).
Assertion (A): Hybrid vigor (heterosis) results in superior performance of hybrids over parents.
Reason (R): Hybrids are always completely homozygous.

In light of the above statements, choose the correct answer:

1. Both (A) and (R) are true and (R) is the correct explanation of (A)
2. Both (A) and (R) are true but (R) is NOT the correct explanation of (A)
3. (A) is true but (R) is false
4. (A) is false but (R) is true

A1: 1
A2: 2
A3: 3
A4: 4

Answer: A3: 3

Explanation: Heterosis leads to better yield, vigor, and adaptability in hybrids. However, hybrids are heterozygous, not homozygous, so the reason is incorrect.

 

 

Objective Question 57

Given below are two statements:
Statement (I): Pathological wilt is usually irreversible leading to the death of plants.
Statement (II): Physiological wilt too is reversible prior to the permanent wilting point.
In light of the above statements, choose the most appropriate answer from the options given below.

1. Both Statement (I) and Statement (II) are correct.
2. Both Statement (I) and Statement (II) are incorrect.
3. Statement (I) is correct but Statement (II) is incorrect.
4. Statement (I) is incorrect but Statement (II) is correct.

Correct Option: 1

Explanation: Pathological wilt (caused by pathogens like Fusarium, Ralstonia) damages vascular tissues and is irreversible, leading to plant death. Physiological wilt (due to water stress) is temporary and reversible before reaching permanent wilting point.

 

 

Objective Question 58

Given below are two statements:
Statement (I): RNA is the only genetic element in plant viruses.
Statement (II): RNA viruses are known to cause crop losses.
In light of the above statements, choose the most appropriate answer from the options given below.

1. Both Statement (I) and Statement (II) are correct.
2. Both Statement (I) and Statement (II) are incorrect.
3. Statement (I) is correct but Statement (II) is incorrect.
4. Statement (I) is incorrect but Statement (II) is correct.

Correct Option: 4

Explanation: Statement (I) is incorrect because some plant viruses contain DNA (e.g., Cauliflower mosaic virus). Statement (II) is correct since RNA viruses are major plant pathogens causing significant yield losses.

 

 

Objective Question 59

Given below are two statements:
Statement (I): Transboundary pathogen triggered plant disease epidemics is responsible for famine in Europe in 19th century.
Statement (II): Invasive pathogens are highly aggressive.
In light of the above statements, choose the most appropriate answer from the options given below.

1. Both Statement (I) and Statement (II) are correct.
2. Both Statement (I) and Statement (II) are incorrect.
3. Statement (I) is correct but Statement (II) is incorrect.
4. Statement (I) is incorrect but Statement (II) is correct.

Correct Option: 1

Explanation: The Irish potato famine was caused by Phytophthora infestans, a transboundary pathogen. Invasive pathogens often lack natural checks in new environments, making them highly aggressive and epidemic-prone.

 

 

Objective Question 60

Given below are two statements:
Statement (I): Phytoplasmas are wall less bacteria.
Statement (II): Phytoplasma do possess flagella.
In light of the above statements, choose the most appropriate answer from the options given below.

1. Both Statement (I) and Statement (II) are correct.
2. Both Statement (I) and Statement (II) are incorrect.
3. Statement (I) is correct but Statement (II) is incorrect.
4. Statement (I) is incorrect but Statement (II) is correct.

Correct Option: 3

Explanation: Phytoplasmas are wall-less bacteria (Mollicutes), so Statement (I) is correct. They lack flagella and are non-motile, so Statement (II) is incorrect.

 

 

Objective Question 61

Given below are two statements, one is labelled as Assertion (A) and other one labelled as Reason (R).

Assertion (A): Polyploidy plays an important role in the evolution of crop plants.
Reason (R): Polyploid plants often show increased size, vigor, and adaptability compared to diploid plants.

In light of the above statements, choose the correct answer from the options given below:

1. Both (A) and (R) are true and (R) is the correct explanation of (A)
2. Both (A) and (R) are true but (R) is NOT the correct explanation of (A)
3. (A) is true but (R) is false
4. (A) is false but (R) is true

A1: 1
A2: 2
A3: 3
A4: 4

Answer: A1: 1

Explanation: Polyploidy leads to genetic variation and speciation in plants. It often results in larger cell size, increased vigor (gigas effect), and better adaptability, which explains its importance in crop evolution.

 

 

Objective Question 62

Which of the following processes is responsible for the fixation of atmospheric nitrogen in leguminous plants?

1. Photosynthesis
2. Respiration
3. Symbiotic nitrogen fixation
4. Transpiration

A1: 1
A2: 2
A3: 3
A4: 4

Answer: A3: 3

Explanation: Leguminous plants form a symbiotic association with Rhizobium bacteria, which fix atmospheric nitrogen into usable forms like ammonia, enriching soil fertility.

 

 

Objective Question 63

Given below are two statements :
Statement (I) : Plasma membrane in bacteria is composed of double layer of phospholipid molecules.
Statement (II) : Plasma membrane is the site of enzymes involved in energy production in bacteria.
In light of the above statements, choose the most appropriate answer from the options given below.

1. Both Statement (I) and Statement (II) are false.
2. Both Statement (I) and Statement (II) are true.
3. Statement (I) is true but Statement (II) is false.
4. Statement (I) is false but Statement (II) is true.

Correct Option: 2

Explanation: Bacterial plasma membrane is a phospholipid bilayer. Since bacteria lack mitochondria, respiratory enzymes are located in the plasma membrane, making it the site of energy production.

 

 

Objective Question 64

Given below are two statements :
Statement (I) : Saccharomyces cerevisiae used in baking industry is a multicellular fungus.
Statement (II) : Both haploid and diploid cells of Saccharomyces cerevisiae may divides asexually by budding.
In light of the above statements, choose the most appropriate answer from the options given below.

1. Both Statement (I) and Statement (II) are true.
2. Both Statement (I) and Statement (II) are false.
3. Statement (I) is true but Statement (II) is false.
4. Statement (I) is false but Statement (II) is true.

Correct Option: 4

Explanation: Saccharomyces cerevisiae is a unicellular fungus, so Statement (I) is false. Both haploid and diploid forms reproduce by budding, so Statement (II) is correct.

 

 

Objective Question 65

Match List-1 with List-11
List-1 (Fungi) List-11 (Importance)
(A) Pleurotus ostreatus                 (I) Phytopathogenic
(B) Magnaporthe oryzae               (II) Entomopathogenic
(C) Rhizophagus irregularis          (III) Edible
(D) Metarhizium                            (IV) Mycorrhizal

Choose the correct answer from the options given below :

1. (A) – (I), (B) – (II), (C) – (IV), (D) – (III)
2. (A) – (III), (B) – (II), (C) – (I), (D) – (IV)
3. (A) – (I), (B) – (III), (C) – (IV), (D) – (II)
4. (A) – (III), (B) – (I), (C) – (IV), (D) – (II)

 

Correct Option: 4

Explanation:

• Pleurotus ostreatus → edible mushroom
• Magnaporthe oryzae → rice blast pathogen
• Rhizophagus irregularis → mycorrhizal fungus
• Metarhizium → entomopathogenic fungus (insect pathogen)

 

 

Objective Question 65

Given below are two statements, one is labelled as Assertion (A) and other one labelled as Reason (R).

Assertion (A): Enzymes have an optimum temperature at which their activity is maximum.
Reason (R): High temperatures always increase enzyme activity without any limit.

In light of the above statements, choose the correct answer from the options given below:

1. Both (A) and (R) are true and (R) is the correct explanation of (A)
2. Both (A) and (R) are true but (R) is NOT the correct explanation of (A)
3. (A) is true but (R) is false
4. (A) is false but (R) is true

A1: 1
A2: 2
A3: 3
A4: 4

Answer: A3: 3

Explanation: Enzymes function best at an optimum temperature. Beyond this, high temperature causes denaturation, reducing activity. Thus assertion is true, but reason is incorrect.

 

 

Objective Question 66

Which of the following is the main function of stomata in plants?

1. Absorption of nutrients
2. Transport of water
3. Exchange of gases and transpiration
4. Storage of food

A1: 1
A2: 2
A3: 3
A4: 4

Answer: A3: 3

Explanation: Stomata regulate gas exchange (CO₂ and O₂) and control transpiration (water loss), playing a key role in photosynthesis and water balance.

 

 

Objective Question 67

Given below are two statements:

Statement (I): DNA is composed of nucleotides containing sugar, phosphate, and nitrogenous bases.
Statement (II): RNA contains thymine instead of uracil.

In light of the above statements, choose the most appropriate answer from the options given below:

1. Both Statement (I) and Statement (II) are true
2. Both Statement (I) and Statement (II) are false
3. Statement (I) is true but Statement (II) is false
4. Statement (I) is false but Statement (II) is true

A1: 1
A2: 2
A3: 3
A4: 4

Answer: A3: 3

Explanation: DNA is made of nucleotides (sugar + phosphate + base), so Statement I is correct. RNA contains uracil instead of thymine, so Statement II is incorrect.

 

 

Objective Question 68

Which of the following is a major function of nitrogen in plants?

1. Cell wall formation
2. Protein synthesis
3. Water absorption
4. Fruit ripening

A1: 1
A2: 2
A3: 3
A4: 4

Answer: A2: 2

Explanation: Nitrogen is a key component of amino acids, proteins, nucleic acids, and chlorophyll, making it essential for plant growth and metabolism.

 

Objective Question 69

Which of the following is involved in the transfer of amino acids from cytoplasm to the ribosome for protein synthesis ?

1. mRNA
2. rRNA
3. tRNA
4. siRNA

Correct Option: 3

Explanation: tRNA (transfer RNA) carries specific amino acids to the ribosome and matches them with codons on mRNA during translation, enabling protein synthesis

 

 

Objective Question 70

Given below are two statements, one is labelled as Assertion (A) and other one labelled as Reason (R).

Assertion (A): Auxins play an important role in apical dominance in plants.
Reason (R): Auxins produced at the apical bud inhibit the growth of lateral buds.

In light of the above statements, choose the correct answer from the options given below:

1. Both (A) and (R) are true and (R) is the correct explanation of (A)
2. Both (A) and (R) are true but (R) is NOT the correct explanation of (A)
3. (A) is true but (R) is false
4. (A) is false but (R) is true

A1: 1
A2: 2
A3: 3
A4: 4

Answer: A1: 1

Explanation: Auxins synthesized in the apical bud suppress the growth of lateral buds, a phenomenon known as apical dominance. When the apical bud is removed, lateral buds grow due to reduced auxin concentration.

 

Objective Question 71

Given below are two statements :
Statement (I): Irradiation of DNA with UV light cause formation of covalent bond between the thymine molecules on the same strand.
Statement (II): Thiamine dimerization in DNA caused by UV radiations can be reverted by Photo- reactivation.
In light of the above statements, choose the most appropriate answer from the options given below.

1. Both Statement (I) and Statement (II) are false.
2. Both Statement (I) and Statement (II) are true.
3. Statement (I) is true but Statement (II) is false.
4. Statement (I) is false but Statement (II) is true.

Correct Option: 2

Explanation: UV radiation causes formation of thymine dimers (covalent linkage between adjacent thymine bases), which distort DNA structure. These can be repaired by photoreactivation using photolyase enzyme, which breaks the dimer using light energy.

 

 

Objective Question 72

Microbes which consume organic molecules for carbon and energy are called ?

1. Chemolithotrophs
2. Photoautotrophs
3. Chemoautotrophs
4. Chemoheterotrophs

Correct Option: 4

Explanation: Chemoheterotrophs obtain both energy and carbon from organic compounds. In contrast, chemoautotrophs use inorganic compounds and photoautotrophs use light energy.

 

 

Objective Question 73

How many nucleotides will be present in a double stranded DNA fragment of 2 kb ?

1. 1000
2. 2000
3. 4000
4. 500

Correct Option: 3

Explanation: 1 kb = 1000 base pairs. Since DNA is double stranded, each base pair has 2 nucleotides, so 2 kb = 2000 bp = 4000 nucleotides.

 

 

Objective Question 74

Given below are two statements, one is labelled as Assertion (A) and other one labelled as Reason (R).

Assertion (A): Transpiration pull is an important force for the upward movement of water in plants.
Reason (R): Water molecules exhibit cohesion and adhesion, forming a continuous column in xylem vessels.

In light of the above statements, choose the correct answer from the options given below:

1. Both (A) and (R) are true and (R) is the correct explanation of (A)
2. Both (A) and (R) are true but (R) is NOT the correct explanation of (A)
3. (A) is true but (R) is false
4. (A) is false but (R) is true

A1: 1
A2: 2
A3: 3
A4: 4

Answer: A1: 1

Explanation: Transpiration pull generates a negative pressure that pulls water upward through the xylem. This is possible because of cohesion (water-water attraction) and adhesion (water-wall attraction), which maintain a continuous water column. Thus, the reason correctly explains the assertion.

 

Objective Question 75

Given below are two statements, one is labelled as Assertion (A) and other one labelled as Reason (R).
Assertion (A): In Bacillus culture raised in a chemically defined medium, sporulation is initiated in the stationary phase.
Reason (R): Lack of nutrients and high cell density trigger sporulation.
In light of the above statements, choose the correct answer from the options given below.

1. Both (A) and (R) are true and (R) is the correct explanation of (A).
2. Both (A) and (R) are true and (R) is not the correct explanation of (A).
3. (A) is true but (R) is false.
4. (A) is false but (R) is true.

Correct Option: 1

Explanation: In Bacillus, sporulation begins during stationary phase when nutrients are depleted. High cell density and stress conditions trigger spore formation, so Reason correctly explains Assertion.

 

 

Objective Question 76

Which of the following association is favourable for P nutrition in higher plants ?

1. Rhizobium-Legume symbiosis
2. Azolla-Anabaena symbiosis
3. Actinorrhizal symbiosis
4. Mycorrhizal association

Correct Option: 4

Explanation: Mycorrhizae enhance phosphorus uptake by increasing root surface area and solubilizing phosphorus, making it available to plants.

 

 

Objective Question 77

Given below are two statements :
Statement (I): Viral genome is protected by protein shell known as capsid.
Statement (II): Viruses can be used as vectors to transfer foreign gene into plants.
In light of the above statements, choose the most appropriate answer from the options given below.

1. Both Statement (I) and Statement (II) are true.
2. Both Statement (I) and Statement (II) are false.
3. Statement (I) is true but Statement (II) is false.
4. Statement (I) is false but Statement (II) is true.

Correct Option: 1

Explanation: Viruses have a protein coat (capsid) protecting their genetic material. They are also used as gene transfer vectors in genetic engineering.

 

 

Objective Question 78

Given below are two statements :
Statement (I): Biogas is a mixture of CH₄, CO₂ and H₂
Statement (II): Biogas is produced by aerobic digestion of organic waste material.
In light of the above statements, choose the most appropriate answer from the options given below.

1. Both Statement (I) and Statement (II) are false.
2. Both Statement (I) and Statement (II) are true.
3. Statement (I) is true but Statement (II) is false.
4. Statement (I) is false but Statement (II) is true.

Correct Option: 3

Explanation: Biogas contains methane, CO₂, and traces of H₂, so Statement (I) is correct. It is produced under anaerobic conditions, not aerobic, so Statement (II) is false.

 

 

Objective Question 79

According to Koch’s first postulate

1. The same disease causing agent must be isolated from experimentally infected animal
2. The isolated causative agent of the disease must be able to produce disease when injected into healthy animal
3. The causative agent of the disease must be present in every diseased animal
4. The disease causing agent must be isolated from diseased animal and grown in pure culture

Correct Option: 3

Explanation: Koch’s first postulate states that the pathogen must be present in all diseased individuals and absent in healthy ones.

 

Objective Question 80

Which of the following plant hormones is primarily responsible for fruit ripening?

1. Auxin
2. Gibberellin
3. Ethylene
4. Cytokinin

A1: 1
A2: 2
A3: 3
A4: 4

Answer: A3: 3

Explanation: Ethylene is a gaseous plant hormone that regulates fruit ripening, especially in climacteric fruits like banana, mango, and tomato. It accelerates processes like softening, color change, and sugar accumulation.