C3.1 Integration of body systems
Practice exam-style IB Biology questions for Integration of body systems, aligned with the syllabus and grouped by topic.
Question 1
A hormone released into the blood affects only some organs. What explains this specificity?
A.
Hormones are destroyed before reaching non-target organs.
B.
Hormones travel only through nerves to one organ.
C.
Only target cells have receptors for the hormone.
D.
Only target cells contain blood capillaries.
Question 2
What is the main role of the cerebellum in movement?
A.
Secreting epinephrine before vigorous activity
B.
Coordinating timing and precision of skeletal muscle contraction
C.
Detecting blood pressure in the carotid arteries
D.
Initiating peristalsis throughout the gut wall
Question 3
What is a role of grey matter in the spinal cord?
A.
Processing information at synapses in unconscious reflexes
B.
Producing melatonin during darkness
C.
Transporting hormones from glands to target organs
D.
Insulating nerve fibres in peripheral nerves
Question 4
In a pain reflex arc withdrawing the hand from a hot surface, what is the effector?
A.
Medulla oblongata in the brainstem
B.
Interneuron in the spinal cord
C.
Skeletal muscle of the arm
D.
Free sensory nerve ending in the skin
Question 5
During exercise, carbon dioxide production increases. What directly explains the resulting increase in ventilation rate?
A.
Oxygen raises blood pH, inhibiting the diaphragm.
B.
Melatonin stimulates intercostal muscles to contract faster.
C.
Carbon dioxide lowers blood pH, stimulating chemoreceptors.
D.
Baroreceptors detect glucose concentration in the aorta.
Question 6
A shoot is illuminated from one side and curves toward the light. What caused the curvature?
A.
Cells on the shaded side elongated faster than cells on the illuminated side.
B.
Cells on the illuminated side divided by meiosis more rapidly.
C.
Ethylene diffused away from the light and hardened cell walls.
D.
Root tips detected light and inhibited shoot growth.
Question 7
Ethylene production during ripening fruit is an example of positive feedback because:
A.
ethylene is transported only in xylem vessels
B.
ethylene stimulates ripening, and ripening stimulates more ethylene production
C.
ethylene reduces ripening once the fruit becomes soft
D.
ethylene only acts on fruits with no receptors
Question 8
A labelled drawing of seedling shoots bending toward a lamp is best classified as:
A.
qualitative observation
B.
quantitative observation
C.
positive feedback data
D.
a controlled variable
Question 9
State the level of organization formed by several tissues working together.
[1]
Outline why a cheetah’s ability to catch prey is an emergent property.
[1]
Question 10
The expected pattern of melatonin secretion in a normal light–dark cycle is best described as:
A.
low during daytime and higher during darkness
B.
released only during vigorous activity
C.
high during daytime and low at night
D.
constant throughout 24 hours
Question 11
Blood pressure rises above the normal range. What response is expected from negative feedback control of heart rate?
A.
Reduced stroke volume caused by the enteric nervous system
B.
Increased heart rate following chemoreceptor input to the cerebellum
C.
Reduced heart rate following baroreceptor input to the medulla
D.
Increased ventilation rate caused by melatonin secretion
Question 12
What best describes control of peristalsis after food has been swallowed?
A.
It is caused by epinephrine secretion from the pancreas.
B.
It is mainly coordinated involuntarily by the enteric nervous system.
C.
It is consciously controlled by the cerebral hemispheres throughout the gut.
D.
It is initiated by baroreceptors in the carotid arteries.
Question 13
What is the function of auxin efflux carriers in plant tissues?
A.
They convert ethylene into cytokinins during ripening.
B.
They digest cellulose cross-links in the apoplast.
C.
They actively transport auxin out of cells to help maintain gradients.
D.
They detect gravity in root caps by absorbing starch grains.
Question 14
After the shoot tip of a young plant is removed, lateral buds grow more strongly. What explains this?
A.
Auxin changes into melatonin in the leaves.
B.
Cytokinin production in root tips stops completely.
C.
Ethylene production in fruits becomes negative feedback.
D.
Auxin from the shoot tip is reduced, so inhibition of lateral buds decreases.
Question 15
What is a phytohormone?
A.
A receptor cell that detects light in animal retina
B.
A plant signalling chemical controlling growth, development or responses to stimuli
C.
An animal hormone transported only through the xylem
D.
A mineral ion required for chlorophyll synthesis
Question 16
Distinguish between nervous and hormonal signalling in animal body-system integration. [3]
Question 17
State one type of input processed by the brain during movement.
[1]
Outline the role of the brain in learning and memory.
[1]
Question 18
The diagram shows a transverse section of a peripheral nerve.
Identify the outer protective sheath.
[1]
Identify one feature that distinguishes a myelinated nerve fibre from an unmyelinated fibre.
[1]
State why many peripheral nerves can carry impulses in both directions between the body and CNS.
[1]
Question 19
Outline how epinephrine prepares the body for vigorous activity. [3]
Question 20
A student records seedling phototropism using photographs and angle measurements.
Distinguish between qualitative and quantitative observations in this investigation.
[1]
State one factor that could limit accuracy of the angle measurements.
[1]
Question 21
Define phytohormone.
[1]
State one role of auxin, cytokinin and ethylene.
[1]
Question 22
The graph shows plasma melatonin concentration in healthy adults over 24 hours.
State when melatonin concentration is highest.
[1]
Describe the overall relationship between light period and melatonin concentration.
[1]
Suggest how exposure to bright light late at night could affect sleep timing.
[1]
Question 23
Seedlings were grown with light from one side. Curvature angle was measured after 48 hours.
| Treatment | Mean angle / ° | Range / ° | Sample size / n |
|---|---|---|---|
| Lateral light | 42 | 28–57 | 24 |
| Overhead light | 6 | 0–14 | 24 |
| Darkness | 3 | 0–9 | 24 |
Identify the treatment with the greatest mean curvature.
[1]
Describe the effect of increasing sample size on confidence in the mean.
[1]
Suggest two improvements to increase reliability of this investigation.
[1]
State whether curvature angle is qualitative or quantitative data.
[1]
Question 24
Auxin promotes cell elongation in shoots by:
A.
causing ethylene gas to polymerize into cellulose
B.
stimulating hydrogen ion secretion into the apoplast, loosening wall cross-links
C.
blocking all active transport across the plasma membrane
D.
reducing turgor pressure so cellulose microfibrils collapse inward
Question 25
A student measures seedling curvature angles from photographs. What change would most improve reliability?
A.
Using seedlings of many different ages in one trial
B.
Removing the fixed distance between lamp and seedlings
C.
Measuring each photograph with a different protractor scale
D.
Using more seedlings of similar age and calculating a mean angle
Question 26
Explain how a pain reflex arc withdraws a hand from a damaging stimulus before conscious analysis of pain. [4]
Question 27
Explain how baroreceptors contribute to negative feedback control of heart rate when blood pressure is too high. [4]
Question 28
State one part of digestive movement that is under voluntary control by the CNS.
[1]
Explain how the enteric nervous system coordinates peristalsis between swallowing and egestion.
[1]
Question 29
Explain positive phototropism in a shoot exposed to lateral light. [4]
Question 30
Outline how auxin and cytokinin help integrate root and shoot growth. [4]
Question 31
Explain why ethylene production during fruit ripening is described as positive feedback and state one biological benefit. [4]
Question 32
A student used a spirometer to record breathing before and after stepping exercise.
State one variable from the trace that can be used to estimate ventilation rate.
[1]
Describe the change in ventilation after exercise.
[1]
Explain why this change helps maintain blood pH.
[1]
Question 33
The table shows cardiovascular measurements in a person while resting, standing suddenly and after recovery.
| Time interval | Systolic blood pressure / mmHg | Heart rate / beats min⁻¹ |
|---|---|---|
| Resting, before standing | 118 | 68 |
| 0–15 s after standing | 92 | 88 |
| 15–30 s after standing | 104 | 96 |
| 30–60 s after standing | 112 | 82 |
| 2–3 min after standing | 116 | 72 |
Identify the time interval when blood pressure is lowest.
[1]
Describe the change in heart rate when blood pressure falls.
[1]
Suggest how baroreceptor feedback explains this response.
[1]
Question 34
Two-point discrimination thresholds were measured on four body regions.
Identify the body region with the smallest receptive fields.
[1]
Describe the relationship between threshold distance and sensitivity to touch.
[1]
Suggest one reason why fingertips differ from the shoulder in this test.
[1]
Question 35
Segments of young shoot tissue were placed in solutions with different auxin concentrations. Mean cell length was measured after 6 hours.
Describe the relationship shown at low to moderate auxin concentrations.
[1]
Explain the mechanism by which auxin causes the observed change in cell length.
[1]
Question 36
Unripe bananas were stored either alone or with one ripe banana. Ethylene concentration and peel colour were recorded over several days.
| Time / d | Ethylene alone / µL L⁻¹ | Peel index alone / 1-7 | Ethylene with ripe / µL L⁻¹ | Peel index with ripe / 1-7 |
|---|---|---|---|---|
| 0 | 0.2 | 1 | 0.2 | 1 |
| 1 | 0.2 | 1 | 0.6 | 1 |
| 2 | 0.3 | 1 | 2.5 | 2 |
| 3 | 0.5 | 2 | 8.0 | 4 |
| 4 | 1.2 | 2 | 18.0 | 6 |
| 5 | 4.0 | 3 | 25.0 | 7 |
| 6 | 10.0 | 5 | 22.0 | 7 |
| 7 | 18.0 | 6 | 18.0 | 7 |
| 8 | 24.0 | 7 | 14.0 | 7 |
Describe the difference in ethylene concentration between the two treatments.
[1]
Describe the difference in ripening time between the two treatments.
[1]
Explain how the results show positive feedback in fruit ripening.
[1]
Question 37
Explain how auxin efflux carriers can create an auxin concentration gradient across plant tissue. [4]
Question 38
Explain how auxin promotes elongation of shoot cells. [4]
Question 39
A tropism experiment using seedlings gives highly variable curvature angles.
Suggest three changes to improve precision, accuracy or reliability.
[1]
Question 40
The graph shows changes in blood flow to selected organs after injection of epinephrine at time 0.
State which tissue shows the largest increase in blood flow.
[1]
Describe the change in blood flow to the gut.
[1]
Explain how these changes prepare the body for vigorous activity.
[1]
Question 41
A fluorescent marker was used to show the position of auxin efflux carriers in cells of a shoot tip exposed to lateral light.
Describe the distribution of efflux carriers shown in the diagram.
[1]
Predict the side of the shoot where auxin concentration will become higher.
[1]
Explain how carrier distribution can lead to curvature toward light.
[1]
Question 42
Lateral bud growth was measured in plants with intact shoot tips, removed shoot tips, or removed shoot tips plus applied auxin or cytokinin.
Identify the treatment with the greatest lateral bud growth.
[1]
Describe the effect of applying auxin after shoot tip removal.
[1]
Discuss how the data support antagonistic interaction between auxin and cytokinin.
[1]
Question 43
Outline two ways in which blood contributes to integration of organs in animals.
[1]
Compare and contrast nervous and endocrine signalling in body-system integration.
[1]
Question 44
Outline how carbon dioxide affects blood pH.
[1]
Explain feedback control of ventilation rate following sensory input from chemoreceptors.
[1]
Question 45
Define negative feedback and positive feedback.
[1]
Discuss the role of feedback and signalling in integrating body systems, using examples from this topic.
[1]
Question 46
State the locations and stimuli detected by baroreceptors and chemoreceptors involved in heart-rate control.
[1]
Explain how sensory input is used to regulate heart rate by negative feedback.
[1]
Question 47
Distinguish between qualitative and quantitative observations in seedling tropism experiments.
[1]
Explain how lateral light leads to positive phototropism in shoots.
[1]
Question 48
State where auxin and cytokinin are produced and the general direction in which each is transported.
[1]
Discuss how interactions between auxin and cytokinin regulate root and shoot growth.
[1]
Question 49
Outline three changes that occur during fruit ripening.
[1]
Evaluate the role of ethylene positive feedback in fruit ripening and its biological benefit.
[1]
Question 50
State two properties of auxin movement into and out of plant cells.
[1]
Explain how auxin efflux carriers and auxin action on cell walls produce shoot curvature in phototropism.
[1]
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