IBBiologyDPSLExam QuestionsInteraction & InterdependenceIntegration of Body Systems

Integration of Body Systems (DP IB Biology: SL): Exam Questions

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Integration of Body Systems

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1a
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The graph below shows changes in levels of the hormone melatonin over a 24-hour period. Blood melatonin concentration is measured in picograms per ml.

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Calculate the percentage increase in melatonin concentration between 2 pm and 12 am.

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1b1 mark

Identify one physiological changes that would occur between 2 pm and 3 am in the body of an individual with the melatonin levels shown in part a).

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1c1 mark

Another hormone is thyroxin.

Identify the gland that secretes thyroxin.

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1d2 marks

Outline the part played by thyroxin in regulating body temperature.

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1a2 marks

Outline how peristalsis ensures one way movement of food through the alimentary canal.

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1b3 marks

An increase in blood CO2 concentration was detected in the chemoreceptors of a person's medulla.

(i) State how this change in CO2 concentration is detected.

(ii) This change caused the person's breathing rate to increase by 38.5% up to 18 breaths per minute.

Calculate the person's breathing rate before the increase in blood CO2 concentration. State your answer to the nearest whole number. 

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1a3 marks

A group of students investigated the effect of a person's fitness level on the heart rate before, during and after exercising. They measured the resting heart rate of an unfit person leading a sedentary lifestyle and that of a trained athlete. After monitoring their resting heart rate for 10 minutes, both participants were asked to run for a period of 10 minutes. Their heart rates were monitored during this time by a heart rate monitor that was attached to their wrists. After exercising, their heart rates were monitored for a period of 40 minutes.

The results of this investigation is shown in the following graph.

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Contrast the results of the two participants.

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1b3 marks

Explain the mechanisms that caused the change in heart rate that was observed after the exercise ended.

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1c3 marks

The group of students concluded that an increased fitness level enables the heart to recover more quickly after exercise.

Evaluate the conclusion of the students.

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