General Science Questions and Answers

Answer: C

A solar eclipse occurs when the moon comes between the sun and the earth, casting its shadow on the earth's surface.

This can happen only at new moon. When the earth comes between the sun and the moon, the moon passes into the earth's shadow and there is a lunar eclipse instead.

Answer: C

The speed of light in a medium remains unaltered by a change in the medium's temperature, to any appreciable degree.

It depends on the medium's refractive index, which is set by its optical density rather than by its temperature. In vacuum the speed is a fixed constant, 3 × 10⁸ m/s.

Answer: B

Stainless steel is an alloy, and an alloy is a homogeneous mixture - iron with about 11 per cent chromium and often nickel, mixed uniformly at the atomic level.

It is not a compound, because the constituents are not combined in a fixed proportion and can be varied continuously. The chromium forms an invisible oxide film that makes the steel stainless.

Answer: C

Chlorophyll is carried in the quantosomes, the pigment-bearing units embedded in the thylakoid membranes of the chloroplast.

Each quantosome holds about 230 chlorophyll molecules and is regarded as the physical unit of photosynthesis. Mitochondria, centrosomes and lysosomes contain no chlorophyll.

Answer: D

Saturn has the great ring system, bright enough to be seen in a small telescope. The rings are about 280,000 km across but only tens of metres thick, and are made of countless pieces of water ice.

Jupiter, Uranus and Neptune also have rings, but all three are faint and were discovered only in the twentieth century.

Answer: B

The nephron is the functional and structural unit of the kidney. Each human kidney contains about a million of them.

A nephron consists of a glomerulus, where blood is filtered, and a tubule, where water and useful solutes are reabsorbed and the remainder passes on as urine. A neuron is a nerve cell, not a kidney unit.

Answer: A

Stress accumulating along the boundaries of lithospheric plates is released as earthquakes. The rocks lock, strain builds, and eventually the fault slips and the stored elastic energy radiates as seismic waves.

This is why the world's earthquake belts trace the plate boundaries almost exactly.

Answer: D

The ostrich is the largest flightless bird - up to 2.7 m tall and 150 kg.

It is also the fastest running bird, at about 70 km/h. The emu is next in size, and the kiwi and the smaller penguins are much smaller.

Answer: D

The fish is the vertebrate with a two-chambered heart - one atrium and one ventricle.

Blood is pumped once, to the gills and then straight on to the body, so the circulation is single. Amphibians have three chambers, and birds and mammals four, which keeps oxygenated and deoxygenated blood completely separate.

Answer: C

White blood cells live about 2 to 15 days, though the span varies greatly with the type - neutrophils survive only hours to a few days, while some lymphocytes persist for years as memory cells.

A normal count is 4,000 to 11,000 per cubic millimetre of blood.