Assertion: Secondary metabolites are used in defense against pathogens, phytoplanktons, improving tolerance to abiotic, etc. Reason: Secondary metabolites are intermediate or indirect products.
Explanation
Option B is correct because both the assertion and reason are true, but the reason does not correctly explain the assertion. The context clearly states that 'Secondary metabolites take part in a variety of functions' including 'defence for protection against pathogens, phytoplanktons and herbivores, to improve tolerance to abiotic stresses' - making the assertion TRUE. The context also states that 'secondary metabolites are intermediates or indirect products, elaborated by entirely different metabolic pathways called secondary metabolic pathways' - making the reason TRUE. However, the reason merely describes the NATURE of secondary metabolites (being intermediate or indirect products), while the assertion describes their FUNCTIONS. The fact that they are intermediate products does not explain WHY they are used in defense or for improving tolerance. These are two separate facts about secondary metabolites mentioned independently in the textbook.
Solution Steps
Step 1: Verify the assertion using context - Secondary metabolites are indeed used in defense against pathogens, phytoplanktons, and for improving tolerance to abiotic stresses (Assertion is TRUE).
Step 2: Verify the reason using context - Secondary metabolites are described as 'intermediates or indirect products' in the textbook (Reason is TRUE).
Step 3: Check if reason explains assertion - The reason describes the nature/origin of secondary metabolites, not why they perform defensive functions. These are independent facts (Reason is NOT the correct explanation).
Step 4: Select Option B - Both true but reason is not the correct explanation.