Biology Questions and Answers

Answer: C

Biofuel is obtained from the seed of Jatropha.

The seeds are about 35 per cent oil, which is transesterified into biodiesel. The plant grows on poor land and does not compete with food crops, which is why India promoted it heavily, though yields have often disappointed.

Answer: A

Organisms that make their own food are autotrophs.

Photoautotrophs, such as green plants and cyanobacteria, use light; chemoautotrophs, such as the nitrifying bacteria, use energy from oxidising inorganic compounds. Everything else in the food chain depends on them.

Answer: A

Botany is also called phytology, from the Greek phyton, plant.

Phycology is the study of algae specifically, and pedology the study of soil.

Answer: D

Most bacteria reproduce by binary fission.

The chromosome is replicated, the two copies move apart, and the cell divides in two. It is asexual, so the daughters are genetically identical, and under good conditions a bacterium can divide every twenty minutes.

Answer: A

Starch is a polysaccharide - a polymer of hundreds or thousands of glucose units.

It occurs as amylose, an unbranched chain, and amylopectin, a branched one. It is the storage carbohydrate of plants; glycogen plays the same role in animals.

Answer: C

Cretinism is a disorder of the thyroid.

Deficiency of thyroxine from birth stunts both physical growth and mental development irreversibly. It is caused by iodine deficiency in the mother or by a failure of the child's own gland, and is now screened for in newborns.

Answer: C

The edible radish is a modified root - a swollen taproot storing food for the plant's second year.

Carrot, beetroot and turnip are the same kind of structure. A bulb is a compressed shoot with fleshy leaves, a corm a swollen stem base, and a tuber a swollen underground stem.

Answer: B

Robert Brown discovered and named the cell nucleus in 1831, while studying orchids.

He is also remembered for Brownian motion, the random movement of pollen grains in water that he described in 1827. Robert Hooke had named the cell itself in 1665.

Answer: A

Bacteria divide by binary fission.

The chromosome is replicated, the copies move apart and the cell divides into two identical daughters. Under good conditions a bacterium may divide every twenty minutes, which is why a colony grows so fast.

Answer: A

In photosynthesis light energy is converted into chemical energy, stored in the bonds of glucose.

\[ \mathrm{6CO_2 + 6H_2O \xrightarrow{light} C_6H_{12}O_6 + 6O_2} \]

It is the entry point for almost all the energy in the living world; respiration then releases it again.