IB Biology SL C3.1 Integration of body systems questions

Exam-style multiple choice and written questions with full markschemes. Check multiple choice answers straight away, or type, photograph or draw a written answer and get it marked.

Type
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Question 1

Paper 2Easy5 marks

A healthy adult’s pineal gland secretes melatonin. The table shows relative melatonin secretion over 24 hours. A student walks along a narrow beam while catching a ball.

TimeRelative melatonin secretion / arbitrary units
08:002
14:001
20:005
02:009
08:00 next day2
(a)

Describe the pattern of melatonin secretion shown in the table.

[1]
(b)

Explain how this pattern helps establish a cycle of sleeping and waking.

[2]
(c)

State two roles of the cerebellum in the student’s movements.

[2]

Question 2

Multiple choiceMedium1 mark

A sharp object touches a hand, which is then withdrawn. The table gives the first time after contact at which activity is detected at each site. Which pathway and response description is consistent with the data?

SiteFirst activity after contact / ms
Sensory neuron entering spinal cord2
Skeletal muscle of arm9
One interneuron in grey matter of spinal cord4
Free sensory nerve ending in hand0
Motor neuron leaving spinal cord6
Show answer and explanation

Answer: D. The activity occurs in sequence at the free sensory nerve ending, sensory neuron, spinal interneuron, motor neuron and skeletal muscle. This is an involuntary pain reflex pathway, with the skeletal muscle as the effector.
A: reverses the order of the interneuron and motor neuron, contrary to their recorded activity times.
B: gives the correct pathway but misclassifies the reflex response as voluntary.
C: substitutes smooth muscle for the skeletal muscle recorded as active.
Remember: a pain reflex passes from a sensory neuron through an interneuron in spinal grey matter to a motor neuron and skeletal muscle.

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