General Science Questions and Answers

Answer: B

Iodine deficiency causes thyroid malfunction. Iodine is needed to make thyroxine, and without it the gland enlarges as it tries to compensate - producing a goitre.

In children the deficiency stunts growth and mental development, which is why salt is iodised.

Answer: D

The pulmonary artery carries impure, deoxygenated blood - from the right ventricle to the lungs.

It is the one artery that does so; the pulmonary vein is likewise the one vein carrying oxygenated blood, from the lungs back to the left atrium. The rule that arteries carry pure blood fails for exactly this pair.

Answer: A

Frederick Banting, with Charles Best, discovered insulin at the University of Toronto in 1921.

They extracted it from dog pancreas and showed it controlled blood sugar in diabetic dogs, then in patients. Banting shared the 1923 Nobel Prize and sold the patent for a dollar.

Answer: B

A lactometer tests the purity of milk. It is a hydrometer calibrated for milk, and measures specific gravity - normally between 1.028 and 1.034.

Adding water lowers the reading, so the instrument detects dilution, though it will not detect skimming, which raises the density instead.

Answer: B

The oxygen released in photosynthesis comes from water, not from carbon dioxide.

In the light reaction water is split - photolysis - to supply electrons and hydrogen, and the oxygen is left over:

\[ \mathrm{2H_2O \rightarrow 4H^+ + 4e^- + O_2} \]

Experiments with the heavy isotope ¹⁸O in the 1940s proved it.

Answer: C

The kiwi of New Zealand is the smallest flightless bird, about the size of a domestic hen at 25 to 45 cm and 1 to 3 kg.

It is also unusual in having nostrils at the tip of its beak and in laying an egg about a fifth of its own body weight.

Answer: D

Bile is produced by the liver and stored in the gall bladder until it is needed.

It contains no digestive enzyme; its bile salts emulsify fat into small droplets so that lipase can act on a much larger surface area. It is released into the duodenum.

Answer: D

The ovum is the largest human cell, about 0.1 mm across - just visible to the naked eye.

It is around twenty times the diameter of a sperm, which is the smallest human cell. The nerve cell is the longest, but not the largest in volume.

Answer: B

Saurology is the study of lizards, from the Greek sauros, lizard - the same root as in dinosaur.

Ophiology covers snakes and entomology insects.

Answer: A

A pheromone is a chemical secreted by an animal that affects the behaviour of other members of its own species - most familiarly, a sex attractant.

A female silk moth's pheromone can draw males from kilometres away, and ants lay pheromone trails to food. Hormones, by contrast, act only within the animal producing them.