Commonly Confused Command Words (Cambridge (CIE) IGCSE Biology): Revision Note

Two individuals measured their heart rate at rest, during a period of exercise, and after the exercise.

Describe the changes in heart rate for person A.

[2]

Zero-mark answer:

• Their heart rate increases in order to pump more blood around the body

• This supplies the muscles with more oxygen and glucose for respiration

Full-mark answer:

• The heart rate increases from (approximately) 35 beats/min at rest to (approximately) 170 beats/min during exercise [1 mark]

• After exercise, the heart rate decreases to back to (approximately) 35 beats/min [1 mark]

The zero-mark answer explains why the heart rate increases, but it does not describe how the heart rate changes, and so scores nothing; it has not met the requirements of the question.

The full-mark answer makes two mark-worthy points describing the change, and using the data given.

Food handlers are told to wash their hands before preparing food.

Explain why washing hands before preparing food reduces the spread of disease.

[2]

Zero-mark answer:

• You would wash your hands with soap and warm water for 20 seconds

• You would then dry them before you touch any food

Full-mark answer:

• Hands can carry pathogens / infectious microorganisms [1 mark]

• Washing removes / kills the pathogens, so they are not passed on to the food and eaten [1 mark]

The zero-mark answer describes how to wash your hands, but the question asks why it matters. Describing the method, however accurately, does not earn marks.

The full-mark answer gains two marks for two separate biological ideas. First, it identifies the problem: pathogens can be present on the hands. Second, it explains how washing solves it: removing the pathogens breaks the route by which they would be transferred to the food and eaten.

Compare the structure of an artery with the structure of a vein.

[2]

Zero-mark answer:

• It has a thick wall because it carries blood at high pressure

Full-mark answer:

• Arteries have thicker walls than veins [1 mark]

• Arteries do not have valves, while veins do [1 mark]

The zero-mark answer only mentions one type of vessel, does not say which vessel "it" is, and gives an explanation that the question did not ask for. This explanation would have taken time to write, and might make a student think that they have written enough to score two marks when they haven't.

The full-mark answer names both vessels in every point, and uses comparative words, such as "thicker" and "while".

The photograph below shows a snowshoe hare, a small mammal native to North America.

Snowshoe hare (Lepus americanus), D. Gordon E. Robertson, converted to black and white, CC BY-SA 3.0, via Wikimedia Commons (opens in a new tab)

Suggest how two adaptive features, visible in the photograph, aid snowshoe hare survival in their environment.

[2]

Zero-mark answer:

• It is adapted to the cold

• It has a good sense of smell to avoid predators

Full-mark answer:

• It has white fur to camouflage it from predators [1 mark]

• It has large feet so it doesn't sink in the snow [1 mark]

The zero-mark answer gives a generic point ("adapted to the cold") that does not identify any feature of the hare. Its second point may be true, but a sense of smell cannot be seen in the photograph, and the question asks for visible features.

The full-mark answer applies knowledge to the specific scenario. The student has not been taught about snowshoe hares, but they use what they know about adaptive features to identify two features and say how each aids survival. They refer to the specific photograph of the hare and its environment throughout.

Note that there are many more correct answers available than the two given here.

A student counted the bubbles of carbon dioxide released by yeast at different temperatures. Their results are shown in the table below.

Predict the number of bubbles per minute at 50 °C.

[1]

Zero-mark answer:

• More bubbles, because the yeast respires faster when it is warmer

Full-mark answer:

• 20 bubbles per minute [1 mark]

The zero-mark answer continues the pattern in the table, but a prediction needs biological knowledge as well as data; at 50 °C the enzymes in the yeast would begin to denature, so the rate would fall rather than keep rising. In addition to this, no bubble number has been predicted, which is what the question has asked for.

The full-mark answer applies knowledge of enzymes and temperature to the data, and predicts a lower value than the one at 40 °C. Any value below 32 would be accepted.