Biology Questions and Answers

Answer: A

Human blood has a pH of about 7.4 - slightly alkaline.

It is held within 7.35 to 7.45 by the bicarbonate buffer system, by the lungs regulating carbon dioxide and by the kidneys excreting acid. Outside about 6.8 to 7.8 life cannot continue.

Answer: B

Respiration proceeds glycolysis → Krebs cycle → electron transport chain.

Glycolysis splits glucose into pyruvate in the cytoplasm; the Krebs cycle oxidises it fully in the mitochondrial matrix, releasing carbon dioxide and reduced coenzymes; and the electron transport chain uses those to make most of the ATP.

Answer: C

The inflorescence of wheat is a spike.

Its flowers are borne in spikelets attached directly to the main axis without stalks, which is what defines a spike. A raceme has stalked flowers, a panicle is a branched raceme, and a catkin is a pendulous spike of unisexual flowers.

Answer: C

Cod liver oil is the richest source of vitamin D.

Vitamin D is fat-soluble and concentrated in the liver oil of fish. The other main source is the skin's own synthesis under sunlight, which supplies most of what people get.

Answer: B

IR-20 is a high-yielding variety of rice.

It came from the International Rice Research Institute in the Philippines, whose IR-8 in 1966 began the rice half of the Green Revolution. The dwarf stem resists lodging under heavy fertiliser.

Answer: A

Red, blue and purple plant colours are usually due to anthocyanins, water-soluble pigments dissolved in the cell sap.

Their colour depends on the pH: red in acid, purple near neutral, blue in alkali. They give roses, beetroot and red cabbage their colour, and autumn leaves much of theirs.

Answer: B

The heart is made of cardiac muscle.

Its fibres are striated like skeletal muscle but branched, uninucleate and joined end to end by intercalated discs, which let the impulse pass from cell to cell so the whole wall contracts as one. It is involuntary and never tires.

Answer: B

Aristotle is called the father of zoology.

His Historia Animalium, De Partibus Animalium and De Generatione Animalium describe and classify animals from direct observation, and his scala naturae was the first systematic arrangement of the animal kingdom.

Answer: C

Bowman's capsule belongs to the excretory system.

It is the cup-shaped start of the nephron, enclosing the glomerulus. Blood is filtered under pressure across the two walls into the capsule, and the filtrate then passes down the tubule, where useful substances are reabsorbed.

Answer: D

The human body has about 700 named skeletal muscles.

They make up roughly 40 per cent of body weight. The count varies with how finely muscles are subdivided; the figure of 206 belongs to the bones, not the muscles.