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BIOLOGY Assertion & Reason

MODEL PAPER 3 · Gujarat Board (GSEB) STD 11 Science (GSEB - English Medium). 4 questions.

Questions

Assertion & Reason

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4 questions · self-marked practice — reveal the answer and mark yourself.

MCQ 11 Mark
Assertion (A): Special vascularised structures called gills are used by most of the aquatic arthropods and molluscs.
Reason (R): Vascularised bags called lungs are used by the terrestrial forms for the exchange of gases.
  • A
    Both A and R are true and R is the correct explanation of A.
  • B
    Both A and R are true but R is not the correct explanation of A.
  • C
    A is true but R is false.
  • D
    A is false but R is true.
Answer
(b) Both A and R are true but R is not the correct explanation of A.
Explanation: Both A and R are true but R is not the correct explanation of A
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MCQ 21 Mark
Assertion (A): Amylase enzyme stops its activity in stomach.
Reason (R): In stomach, pH is acidic due to presence of HCl.
  • A
    Both A and R are true and R is the correct explanation of A.
  • B
    Both A and R are true but R is not the correct explanation of A.
  • C
    A is true but R is false.
  • D
    A is false but R is true.
Answer
(a) Both A and R are true and R is the correct explanation of A.
Explanation: Each enzyme functions at a particular pH. Specificity of pH for enzyme activity is useful in regulating enzymes, e.g., salivary amylase stops its activity in the stomach where hydrochloric acid is secreted. Salivary amylase acts at pH 6.8.
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MCQ 31 Mark
Assertion (A): Inspiration occurs due to muscular relaxation.
Reason (R): During inspiration, the diaphragm and external intercostal muscle contract simultaneously
  • A
    Both A and R are true and R is the correct explanation of A.
  • B
    Both A and R are true but R is not the correct explanation of A.
  • C
    A is true but R is false.
  • D
    A is false but R is true.
Answer
(a) Both A and R are true and R is the correct explanation of A.
Explanation: Inspiration is the result of muscular contraction. The diaphragm and external intercostal muscle contract simultaneously. The lateral thoracic wall moves outward and upward.
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MCQ 41 Mark
Assertion (A): Paroxysms are regular and daily in Quotidian malaria.
Reason (R): Recurrence of fever is after 48 hours, if the infection is caused by Plasmodium malariae.
  • A
    Both A and R are true and R is the correct explanation of A.
  • B
    Both A and R are true but R is not the correct explanation of A.
  • C
    A is true but R is false.
  • D
    Both A and R are false.
Answer
(d) Both A and R are false.
Explanation: In Quotidian malaria, paroxysms are irregular and daily (Recurrence of fever is called paroxysms). Plasmodium malariae causes Quartan malaria. Recurrence of fever is about 72 hours.
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