Biology Questions and Answers

Answer: C

The mitochondrion is the powerhouse of the cell.

It carries out the Krebs cycle and the electron transport chain, producing most of the cell's ATP. Its inner membrane is deeply folded into cristae to give the enzymes room, and it has its own DNA and ribosomes.

Answer: A

Pollination is the transfer of pollen from the anther to the stigma.

It is the transfer itself, not what follows: germination of the pollen grain and growth of the pollen tube down the style come afterwards, and fertilisation is a separate event again.

Answer: C

Cell division takes place by mitosis, and by meiosis in the formation of gametes.

Mitosis produces two daughter cells genetically identical to the parent, and is how an organism grows and repairs itself. Meiosis halves the chromosome number and produces four genetically varied cells.

Answer: D

Water and minerals are transported by the xylem.

Its tracheids and vessels are dead, hollow, lignified cells forming continuous tubes from root to leaf. Water is drawn up by the pull of transpiration, helped by the cohesion between water molecules.

Answer: B

Insect-pollinated flowers have pollen that is rough and sticky, often with spines or a sticky coating, so it clings to a visiting insect.

Wind-pollinated pollen is the opposite: small, smooth, dry and light, produced in enormous quantity so that a little of it reaches a stigma by chance.

Answer: A

The leaves are called the lungs of a plant.

They take in carbon dioxide and give out oxygen through the stomata, and the same pores admit the oxygen the plant needs for its own respiration. Their broad thin form gives the surface area the exchange requires.

Answer: C

Japanese encephalitis is not spread by tiger mosquitoes.

It is carried by Culex, breeding in rice fields, with pigs and wading birds as reservoirs. The Asian tiger mosquito, Aedes albopictus, transmits dengue, chikungunya and yellow fever.

Answer: C

Pathogenic bacteria grow fastest between about 20 and 45°C.

This is the danger zone for food, and it brackets body temperature, 37°C, which is where human pathogens are best adapted to grow. Refrigeration below 5°C slows them and cooking above 70°C kills them.

Answer: B

Epinephrine - adrenaline - is used to treat cardiac arrest.

It constricts the peripheral vessels, raising the pressure that drives blood to the heart and brain during compressions, and stimulates the heart itself. It is given intravenously during resuscitation.

Answer: C

Ranikhet disease, or Newcastle disease, is the commonest poultry disease in India.

It is a viral infection causing respiratory and nervous symptoms and can kill an entire flock. It is named after the Uttarakhand town where it was first reported in India in 1928, and is controlled by vaccination.