(a) Explain how the leaf of a flowering plant is adapted for photosynthesis. (b) Describe briefly the mode of feeding in tapeworm. (c) Name one mineral elem...

(a) How the leaf is adapted for photosynthesis

• Broad, flat lamina gives a large surface area to trap maximum sunlight.
• Thin lamina so that light and gases diffuse quickly to the inner cells.
• Abundant chloroplasts (rich in chlorophyll), especially in the palisade layer, to absorb light energy.
• Palisade cells are elongated and packed near the upper surface to catch the most light.
• Many stomata allow entry of carbon dioxide and exit of oxygen.
• Air spaces in the spongy mesophyll allow rapid diffusion of gases.
• A network of veins (xylem) supplies water and (phloem) removes manufactured food.
• Leaves are arranged in a mosaic (leaf mosaic) to avoid overshadowing one another.

(b) Mode of feeding in tapeworm: the tapeworm lives in the host's small intestine and feeds by absorbing already-digested food (mainly soluble sugars and amino acids) directly through its flat body wall over its whole large surface area. It has no mouth or gut of its own; it secretes anti-enzymes to protect itself from being digested and simply absorbs the host's nutrients (parasitic nutrition).

(c) One mineral element needed for the proper functioning of

• (i) Bones: calcium (phosphorus also acceptable).
• (ii) Red blood cells: iron.
• (iii) Thyroid gland: iodine.

(d)(i) Three benefits of roughage in the diet

• Adds bulk to food and stimulates peristalsis, aiding movement of food through the gut.
• Prevents constipation and helps regular egestion of faeces.
• Helps prevent bowel disorders (such as colon cancer) and absorbs/removes harmful substances.

(ii) Three reasons why proteins are important to humans

• For growth and formation of new cells and tissues.
• For repair of worn-out and damaged tissues.
• For making enzymes, hormones and antibodies.