Biology Questions and Answers

Answer: A

A codon is three nucleotides.

Three bases give \( 4^3 = 64 \) combinations for twenty amino acids and a stop signal, so the code is degenerate - most amino acids have more than one codon. Two bases would give only sixteen, too few.

Answer: C

Darwin observed the finches and giant tortoises on the Galápagos Islands, in 1835.

Each island had its own form, differing in beak or shell, which suggested that one ancestral stock had diverged as it adapted to different conditions. The observation was central to his thinking about the origin of species.

Answer: C

About 7 weeks are needed to replace the body's reserve of red corpuscles after giving a pint of blood.

The plasma volume is restored within a day or two, and the red cell count within a few weeks, but the iron stores that back it up take considerably longer - which is why donors are asked to wait about three months.

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: B

The study of cells is cell biology, also called cytology.

It covers the structure, function and division of cells, and it became possible only with the microscope - Hooke named the cell in 1665 and Schleiden and Schwann framed the cell theory in 1838–39.

Answer: C

Tikka disease affects the groundnut.

It is a leaf spot caused by the fungi Cercospora; dark spots with yellow haloes spread over the leaves, which fall, and the yield drops sharply. It is the most damaging groundnut disease in India.

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.