21.

Assertion: Smoking causes oxygen deficiency in the body.

Reason: Carbon monoxide when inhaled while smoking, combines with haemoglobin to form chemically stable compound.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

Assertion: The immune responses of old persons become weak.

Reason: Thymus is degenerated in old individuals resulting in a decreased production of thymosin

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

Assertion: The enlarged Q and R waves indicate myocardial infarction.

Reason: The QRS complex represents ventricular repolarisation.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

Assertion: The leaves in gymosperms are well adapted to with stand extremes of temperature, humidity and wind.

Reason: Unlike bryophytes and pteridophytes, in gymnosperms the male and female gametophytes do not have an independent free-living existence.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

Assertion: Glucose is the favoured respiratory substrate.

Reason: When glucose is used as respiratory substrate and is completely oxidized, the RQ is 1.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

Assertion: Human heart is myogenic.

Reason: The contraction is initiated by a specialized patch of modified heart muscles without requiring stimulation from nerve cells.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

Assertion: In basidiomycetes, basidiospores are produced endogenously in the basidium.

Reason: In ascomycetes, ascospores are produced exogenously in ascus.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

Assertion: In a pivot joint, rounded or pointed bone fits into a shallow depression in another bone.

Reason: Pivot joints are present between the metacarpals and phalanges of the fingers.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

Assertion: Deficiency symptoms of N, K and Mg are first visible in the senescent leaves.

Reason: Biomolecules containing these elements are broken down in the older leaves, making these elements available for mobilising to younger leaves.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.

Assertion: Photorespiration interferes with the successful functioning of Calvin cycle.

Reason: Photorespiration oxidises ribulose1,5 biphosphate which is an acceptor of CO₂ in Calvin cycle.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false.

• If both assertion and reason are false.