For growth to occur in organisms, the rate of

Step 1: Analyze the question The question asks what must happen to metabolic rates for an organism to grow. It is testing your understanding of the two parts of metabolism.

Step 2: Explain the concept Metabolism is all the chemical reactions in a living organism. It has two parts:

• Anabolism (constructive metabolism): small molecules are built up into larger, complex ones, e.g. amino acids into proteins, or glucose into starch. It uses energy.
• Catabolism (destructive metabolism): large molecules are broken down into smaller ones, e.g. respiration breaking glucose down to release energy.

Step 3: Work through the options Growth is a permanent increase in size, mass, and cell number. This requires new protoplasm, cell walls, enzymes and tissues to be built.

• A. Anabolism must exceed catabolism: Correct. When building up is faster than breaking down, there is a net gain in body materials, so the organism grows.
• B. Catabolism must exceed anabolism: Wrong. This leads to a net loss of body mass, as in starvation or weight loss.
• C. Food storage must be low: Wrong. Low food storage does not by itself cause growth.
• D. Food storage must be high: Wrong. Storing food (e.g. fat in an obese person) is not the same as growth. Growth is the actual building of new tissue.

Step 4: Answer The correct option is A.

Tip: Remember "Anabolism = Assemble" (build up, growth) and "Catabolism = Cut down" (break down, energy release). If anabolism beats catabolism, the organism grows. If they are equal, the organism maintains its size. If catabolism wins, the organism shrinks.