Syllabus Edition
First teaching 2023
First exams 2025
1 markA sycamore tree seed lands on sloping ground at a particular spot, shown as X in the diagrams. Conditions there are favourable to the sycamore seed's germination.
Which diagram of A - D best shows the direction of growth of the tree's shoots and roots in its early life after germination of the seed?
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1 markWhich row of the table gives the most accurate summary of the actions of auxins?
| In shoots | In roots | |
| A. | Cells elongate | Growth inhibited |
| B. | Cells grow in number | Growth inhibited |
| C. | Cells elongate | Growth promoted |
| D. | Cells grow in number | Growth promoted |
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1 markWhich 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 markWhich of A - D gives the most accurate description of how efflux pumps contribute to plant tropisms?
Efflux pumps pump low-density particles to the top of a horizontal root in order to initiate a positive gravitropism.
Light denatures PIN3 proteins which leads to fewer efflux pumps, and hence less cell elongation, on the sunny side of a plant shoot.
Efflux pumps are coded for by PIN3 genes and carry auxins from one cell to another in order to maintain an uneven distribution of auxins.
Efflux pumps carry auxins away from growing tissues on the removal of a stimulus, in order to maintain an even distribution of auxins.
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1 markWhich 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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1 markWhich 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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1 markA 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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1 markA pot plant falls over and after a few days shows the following growth pattern.
Which of the following is the most accurate explanation for the growth shown at each of the labels on the diagram?
This part of the stem demonstrates negative gravitropism in order to receive the maximum amount of sunlight for photosynthesis
This part of the stem shows positive phototropism as it will bend towards the light
The lateral roots demonstrates negative gravitropism as they are not growing towards gravity
The main root shows positive gravitropism as it is bending towards gravity
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1 markWhat would not be considered a function of auxins?
Stimulates cell elongation in shoots, leading to an increase in plant height
Stimulates the development of axillary buds further away from the shoot apical meristem
Inhibits the development of axillary buds close to the shoot apical meristem
Inhibits cell elongation in root cells, therefore slowing down root growth
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1 markWhich would be the most accurate description and explanation for the growth response that would be observed in the shoot tip below?
|
Description |
Explanation |
|
| A |
The shoot tip grows away from the light source |
Auxins inhibit cell elongation on the shady side of the shoot tip |
| B |
The shoot tip grows towards the light source |
Auxins inhibit cell elongation on the side of the light source |
| C |
The shoot tip continues to grow straight up |
Auxins are evenly distributed across the shoot tip |
| D |
The shoot tip grows towards the light source |
Auxins cause cell elongation on the shady side of the shoot tip |
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