Biology Questions and Answers

Answer: A

Tea is the crop India is best known for producing and exporting.

India is the world's second largest producer after China, growing about 1.3 million tonnes a year in Assam, West Bengal and the Nilgiris, and is among the leading exporters.

Answer: C

Phloem is a plant tissue. It carries the sugars made in the leaves to the rest of the plant, in both directions as needed.

Its conducting elements are sieve tubes, living cells whose end walls are perforated, assisted by companion cells. Xylem, the other vascular tissue, carries water upward only.

Answer: A

When the androecium and gynoecium of a bisexual flower mature at different times, the condition is dichogamy.

It prevents self-pollination and so promotes outbreeding. Where the anthers mature first it is protandry; where the stigma does, protogyny. Herkogamy achieves the same end by physical separation instead.

Answer: A

The largest flower in the world is Rafflesia arnoldii, of Sumatra and Borneo.

It reaches a metre across and weighs up to 11 kg. It is a parasite with no leaves, stem or roots of its own, and it smells of decaying flesh to attract the carrion flies that pollinate it.

Answer: A

If blood becomes acidic, the oxygen-carrying capacity of haemoglobin decreases.

This is the Bohr effect: a fall in pH shifts the oxygen dissociation curve to the right, so haemoglobin releases oxygen more readily and binds it less. It is useful in the tissues, but in acidosis it means the lungs load less oxygen too.

Answer: D

Dental caries is linked to a deficiency of fluorine.

Fluoride is incorporated into tooth enamel as fluorapatite, which resists acid better than the ordinary hydroxyapatite. Too much has the opposite effect, causing the mottling of dental fluorosis.

Answer: A

The potato is not a root - it is a stem tuber, the swollen tip of an underground branch, with buds (the eyes) and scale leaves.

Carrot and radish are swollen taproots, and sweet potato is a swollen adventitious root.

Answer: A

A bud is an embryonic shoot - a compressed stem tip with immature leaves or flower parts folded round it, protected by scales.

A terminal bud extends the shoot; axillary buds in the leaf axils give branches.

Answer: C

Photosynthesis is fastest in white light, because it contains every wavelength chlorophyll can use.

Chlorophyll absorbs most strongly in the blue-violet and red, and the accessory pigments capture parts of the spectrum chlorophyll misses, so the full white spectrum drives the process harder than any single colour.

Answer: D

Uttar Pradesh is the leading producer of basmati rice, with Punjab and Haryana close behind.

Basmati is grown only in the Indo-Gangetic plain at the foot of the Himalaya, and has a protected geographical indication limiting it to seven northern states.