IBBiologySLTopic QuestionsInteraction & InterdependenceIntegration of Body Systems

Syllabus Edition

First teaching 2023

First exams 2025

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Integration of Body Systems (SL IB Biology)

Topic Questions

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1
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Which of the following statements about melatonin are correct?

I. Melatonin secretion increases in the evening in response to darkness and decreases at dawn in response to light.

II. Increasing melatonin levels stimulate the body, preparing it for waking up and staying awake during the day.

III. Melatonin is secreted by the hypothalamus.

IV. The night-time drop in core body temperature triggers an increase in melatonin secretion.

V. Melatonin levels vary during a 12-hour cycle known as a circadian rhythm.

  • II, IV and V

  • I, III and IV

  • I only

  • II and V

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1
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Which statement best describes the action of peristalsis in the alimentary canal?

  • Striated muscles contract to move the partially digested food in a wave-like movement along the alimentary canal.

  • Circular muscles contract behind the partially digested food and the longitudinal muscles shorten.

  • Skeletal muscle contractions force the food through the alimentary canal with valves preventing backflow.

  • Longitudinal muscles contract behind the partially digested food and the circular muscles shorten.

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2
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Which statement accurately describes the raising of heart rate by the cardioregulatory centre of the brain?

  • Low blood pressure, high blood oxygen concentration, and high blood pH result in a nerve signal sent by the acceleratory centre to speed up heart rate.

  • Low blood pressure, low blood oxygen concentration, and low blood pH result in a nerve signal sent by the acceleratory centre to speed up heart rate.

  • High blood pressure, high blood oxygen concentration, and high blood pH result in a nerve signal sent by the acceleratory centre to speed up heart rate.

  • High blood pressure, low blood oxygen concentration, and low blood pH result in a nerve signal sent by the acceleratory centre to speed up heart rate.

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3
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A person is admitted to hospital after suffering a stroke. It was found that the suprachiasmatic nucleus in the hypothalamus of the brain was damaged by the event. This resulted in the pineal gland secreting less melatonin into the bloodstream.

Which of the following changes would be observed in the patient?

  • Increased thirst and more frequent urination.

  • Disrupted sleep patterns and increased irritability.

  • Constantly feeling cold and weight gain.

  • Fatigue and forgetfulness.

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