NESA Biology Homeostasis
15 sample questions with marking guides and sample answers · Avg. score: 67.8%
A lizard repeatedly lifts its legs off the warm rock that it is standing on. This is an example of a
physiological response that helps the lizard to increase heat gain through radiation.
physiological response that helps the lizard to decrease heat gain through conduction.
behavioural response that helps the lizard to increase heat gain through radiation.
behavioural response that helps the lizard to decrease heat gain through conduction.
Reveal Answer
physiological response that helps the lizard to increase heat gain through radiation.
Lifting legs is a voluntary action, making it a behavioral response, not an involuntary physiological one. Additionally, this action affects heat transfer via direct contact (conduction), not radiation.
physiological response that helps the lizard to decrease heat gain through conduction.
While this action does decrease heat gain through conduction, lifting legs is a behavioral response, not a physiological process like sweating or vasodilation.
behavioural response that helps the lizard to increase heat gain through radiation.
Although it is a behavioral response, the purpose is to reduce direct contact with the warm rock, which decreases heat gain through conduction rather than increasing it through radiation.
behavioural response that helps the lizard to decrease heat gain through conduction.
Lifting its legs is a voluntary behavioral response that reduces the surface area in direct contact with the warm rock, thereby effectively decreasing heat gain through conduction.
To reduce water loss, xerophytes often have
extensive root systems.
large numbers of root hairs.
leaves with thick cuticles.
large flat leaves.
Reveal Answer
extensive root systems.
While extensive root systems help xerophytes maximize water absorption from deep or widespread soil areas, they do not function to reduce water loss.
large numbers of root hairs.
Large numbers of root hairs increase the surface area for water absorption from the soil, but they do not play a role in preventing water loss.
leaves with thick cuticles.
A thick waxy cuticle on the epidermis of leaves creates a waterproof barrier that significantly reduces water loss through transpiration.
large flat leaves.
Large flat leaves would increase the surface area exposed to the sun and air, which would actually increase water loss through transpiration rather than reduce it.
Homeostatic response mechanisms require the transfer and recognition of information from a sensory receptor and an effector. The transmission of this information
may involve both the endocrine and nervous systems.
relies only on hormones for a short-term response.
is usually a conscious process.
is under control of the autonomic system only.
Reveal Answer
may involve both the endocrine and nervous systems.
This is correct because homeostasis often relies on the integration of both the nervous system for rapid responses and the endocrine system for sustained, long-term regulation.
relies only on hormones for a short-term response.
This is incorrect because hormones, which are part of the endocrine system, typically mediate slower, long-term responses, whereas the nervous system handles rapid, short-term responses.
is usually a conscious process.
This is incorrect because homeostatic mechanisms, such as regulating blood glucose or body temperature, are primarily involuntary and unconscious processes.
is under control of the autonomic system only.
This is incorrect because homeostasis involves multiple systems, including the endocrine system and occasionally the somatic nervous system (such as shivering), not just the autonomic nervous system.
Which of the following is an example of a physiological adaptation in a plant?
closing stomata during the day
stomata located in pits
stomata surrounded by hairs
fewer stomata on upper leaf
Reveal Answer
closing stomata during the day
This is correct because the active opening and closing of stomata is an internal, functional process (often used by CAM plants to conserve water), which defines a physiological adaptation.
stomata located in pits
This is incorrect because the physical location of stomata in sunken pits is a permanent anatomical feature, making it a structural adaptation rather than a physiological process.
stomata surrounded by hairs
This is incorrect because the presence of leaf hairs (trichomes) is a physical characteristic built into the plant's anatomy, which is a structural adaptation.
fewer stomata on upper leaf
This is incorrect because the distribution and quantity of stomata on a leaf are permanent physical traits, classifying this as a structural adaptation.
Chimpanzees use piloerection (raising of body hair) to modify heat exchange with the environment. Piloerection is controlled by muscles around the hair follicles. In a negative feedback loop, these muscles represent
a response.
a sensor.
a stimulus.
an effector.
Reveal Answer
a response.
The response is the actual action or change that occurs, which in this case is piloerection (the raising of the hair), not the muscles themselves.
a sensor.
A sensor (or receptor) detects changes in the environment, such as thermoreceptors in the skin detecting cold, rather than carrying out the physical response.
a stimulus.
A stimulus is the environmental change, such as a drop in temperature, that triggers the negative feedback loop to begin.
an effector.
An effector is a muscle or gland that receives signals from the control center and carries out the physical response to restore homeostasis.
Two unrelated patients; X and Y, visited the same neurosurgeon. The patients had very similar names, and both had a form of brain damage. The neurosurgeon asked Patient X to complete a point-to-point movement test, where the index finger touches the nose and then touches the outstretched finger of the neurosurgeon. He was also asked to walk across the room while the neurosurgeon observed his stability. Patient X found this very strange, as these tests were not what he normally experienced. He has a benign growth below the hypothalamus, reducing levels of thyroid-stimulating hormone. When Patient X questioned this, the neurosurgeon realised he had mixed up the two patients and mistakenly thought he was seeing Patient Y.
Using the information above, identify the part of the brain damaged in both patients (X and Y), describe the role of these parts in normal body functioning and describe the effects damage to these structures would have on both patients.
Reveal Answer
An example response:
For patient X, the affected part is the anterior pituitary. Its role is to produce hormones, release hormones, and maintain homeostasis. The possible effects of damage include hypothyroidism, fatigue, and loss of appetite.
For patient Y, the affected part is the cerebellum, which coordinates voluntary motor movement and maintains balance. Possible effects of damage include weak muscles, slurred, speech, and abnormal eye movements.
Patient X
| Descriptor | Marks |
|---|---|
Identifies the affected part as the Anterior Pituitary | 1 |
1 mark for each correct point (any 2 of):
| 2 |
1 mark for each correct point (any 3 of):
| 3 |
Patient Y
| Descriptor | Marks |
|---|---|
Identifies the affected part as the Cerebellum | 1 |
1 mark for each correct point (any 2 of):
| 2 |
1 mark for each correct point (any 3 of):
| 3 |
Describe how the hypothalamus and pituitary work together to achieve their main function.
Reveal Answer
An example response:
Hormones are produced in the hypothalamus, and are transported down the axons. Hormones are stored in posterior lobe and released via nervous stimulation.
Hormones are produced in the anterior lobe Inhibiting and releasing factors secreted by hypothalamus determine the release of hormones. Blood vessels connect hypothalamus with the anterior lobe, and released via hormonal stimulation.
Posterior pituitary
| Descriptor | Marks |
|---|---|
States that hormones are produced (in cell bodies located) in the hypothalamus or not produced by the pituitary | 1 |
Describes that hormones are transported down the axons or neurosecretory cells | 1 |
States that hormones are stored in the posterior lobe | 1 |
Identifies that they are released via nervous stimulation | 1 |
Anterior pituitary
| Descriptor | Marks |
|---|---|
States that hormones are produced in the anterior lobe | 1 |
Explains that inhibiting and releasing factors secreted by the hypothalamus determine the release of hormones | 1 |
Describes that blood vessels (hypothalamic-hypophyseal portal system) connect the hypothalamus with the anterior lobe or that it travels in the blood | 1 |
Identifies that they are released via chemical or hormonal stimulation | 1 |
Which of the following is an example of a response in a negative feedback loop?
dog panting on a hot day
bear hunting for food
human turning on a light
plant growing towards sunlight
Reveal Answer
dog panting on a hot day
Panting is a physiological response that cools the dog down, counteracting the initial stimulus of high body temperature to maintain homeostasis.
bear hunting for food
While hunger is related to homeostasis, hunting is a complex, voluntary behavior rather than a direct, involuntary physiological negative feedback mechanism.
human turning on a light
Turning on a light is a conscious, voluntary action to alter the external environment, not an internal biological process regulating a physiological set point.
plant growing towards sunlight
A plant growing towards sunlight is an example of phototropism, which is a directional growth response rather than a negative feedback loop designed to reverse a change.
Flynn was standing at second base during a game of baseball. The batter hit the ball straight at him. Without thinking, Flynn put his baseball glove up to stop the ball from hitting his face and his face flinched (involuntarily turned) away from the incoming ball.
Describe the components of the mechanism that produced the flinching response.
Reveal Answer
It is a reflex action so it only involves the spinal cord. Impulse travels from receptor to sponal cord via a sensory neuron through the dorsal root.
Synapse between a sensory neuron and an interneuron in the grey matter of the spinal cord. Synapse between interneuron and motor neuron. And impulse is sent to effector through ventral root. Motor neuron stimulates muscle movement via a neuromuscular junction.
| Descriptor | Marks |
|---|---|
1 mark for each correct point (any 8 of): Reflex action (so only involves the spinal cord); Impulse travels from receptor to spinal cord; via a sensory/afferent neuron; through the dorsal root; Synapse between a sensory/afferent neuron and an interneuron; In the grey matter of the spinal cord; Synapse between interneuron and motor/efferent neuron; Impulse sent to effector through ventral root; Motor/efferent neuron stimulates muscle movement; via a neuromuscular junction/across a motor end plate | 8 |
Explain how a nerve impulse travels along an axon and between neurons.
Reveal Answer
Along the axon:
Depolarisation occurs and reaches threshold. Cell membrane becomes permeable to sodium ions, which diffuse into the cell across the cell membrane. Potassium ions diffuse out of the cell across the membrane. Inside the membrane becomes negative relative to the outside. A sodium-potassium pump transport sodium ions out of the cell transports potassium into the cell. The neuron is repolarised.
Between the neurons:
Action potential reaches axon terminal. Calcium channels open and calcium causes vesicles to release neurotransmitter via exocytosis. Neurotransmitters bind to neuroreceptors on post synaptic dendrite, and action potential triggerred in post synaptic neuron.
Along the axon
| Descriptor | Marks |
|---|---|
1 mark for each correct point (any 7 of): Depolarisation occurs; Reaches threshold/-55 mV; Cell membrane becomes permeable to sodium ions/sodium channels open; Sodium ions diffuse into the cell (across the cell membrane); Inside the cell/membrane becomes positive relative to the outside; Potassium ions diffuse out of the cell (across the membrane)/potassium channels open; Inside the membrane becomes negative relative to the outside; A sodium–potassium pump transports sodium ions out of the cell transports potassium ions into the cell; Returns to a polarised/resting state/neuron repolarised | 7 |
Between neurons
| Descriptor | Marks |
|---|---|
1 mark for each correct point (any 5 of): Action potential reaches axon terminal; Calcium channels open; Calcium causes vesicles to release neurotransmitter (via exocytosis); Neurotransmitter diffuses across synaptic cleft; Neurotransmitters binds to (neuro)receptors on post synaptic dendrite; Action potential triggered in post synaptic neuron | 5 |
Some birds can dilate or constrict the blood vessels in their beaks to control heat exchange with the environment. Smooth muscles constrict the blood vessels. In this example of a negative feedback loop, the diameter of blood vessels is the
response and the smooth muscles are the effector.
response and the smooth muscles are the control centre.
effector and the smooth muscles are the control centre.
effector and the smooth muscles are the stimulus.
Reveal Answer
response and the smooth muscles are the effector.
The change in blood vessel diameter is the physiological response, and the smooth muscles that execute this change act as the effector in the feedback loop.
response and the smooth muscles are the control centre.
While the diameter is the response, the smooth muscles are the effector, not the control center (which is typically the brain or hypothalamus).
effector and the smooth muscles are the control centre.
The blood vessel diameter is the response, not the effector, and the smooth muscles are the effector, not the control center.
effector and the smooth muscles are the stimulus.
The blood vessel diameter is the response, not the effector, and the smooth muscles are the effector, not the stimulus (which would be a change in temperature).
Most xerophytes have
fewer stomata open in the day than in the night.
more stomata open in the day than in the night.
the same number of open stomata in the day and night.
no stomata open during either the day or the night.
Reveal Answer
fewer stomata open in the day than in the night.
Xerophytes are adapted to arid environments and typically open their stomata at night to minimize water loss through transpiration during the hot day.
more stomata open in the day than in the night.
Opening more stomata during the day would result in excessive water loss, which is detrimental to plants living in dry conditions.
the same number of open stomata in the day and night.
Xerophytes actively regulate their stomata based on environmental conditions, keeping them mostly closed during the day and open at night to conserve water.
no stomata open during either the day or the night.
Plants must open their stomata at some point to take in the carbon dioxide required for photosynthesis.
The defining feature of a negative feedback loop is that it acts to
disrupt homeostasis.
change a behaviour.
counter a stimulus.
stimulate a response.
Reveal Answer
disrupt homeostasis.
Incorrect. Negative feedback loops are the primary mechanism used by the body to maintain homeostasis, not disrupt it.
change a behaviour.
Incorrect. While a feedback loop might indirectly result in a behavioral change, its defining physiological purpose is to regulate internal states rather than alter behavior.
counter a stimulus.
Correct. The defining characteristic of a negative feedback loop is that it produces a response that opposes or counters the initial stimulus, returning the system to its set point.
stimulate a response.
Incorrect. Both positive and negative feedback loops stimulate a response; what defines a negative feedback loop is that the response specifically opposes the original stimulus.
While the nervous and endocrine systems work together to co-ordinate the functions of the body systems, they differ in several ways. Contrast three ways in which these systems operate.
Reveal Answer
Answers could include:
- The nervous system is rapid while the endocrine system is slower.
- Nervous system work along neurons while endocrine system works via the blood stream.
- Nervous system responses are usually local and specific to one effector, while endocrine system may be very general and widespread.
| Descriptor | Marks |
|---|---|
2 marks for each correct point (any 3 of):
| 6 |
The autonomic nervous system helps to control homeostatic mechanisms. The effects of these can often be demonstrated consciously. For example, an athlete competing in an important race event noticed the following whilst standing waiting for the race to start; they had a 'funny feeling' in their stomach, they were sweating, the light seemed brighter than usual, and they felt their heart was going to explode.
Outline the neural pathway of the autonomic nervous system activated in the athlete and explain the reasons for these symptoms.
Reveal Answer
The pathway involved is the sympathetic pathway.
Neurons originate in the middle region of the spinal cord, specifically the thoracic and lumbar regions, and leave the spinal cord via the ventral root. They synapse close to the spinal cord with the next neuron, the postganglionic fibre, and release noradrenaline to effect the target organ, involving two motor neurons and one synapse.
The reasons for these responses are to prepare the body for physical work and the activation of fight or flight responses. Sweating was because of the activation of sweat glands to keep the body cool during physical activity. The stomach feeling was due to decreased movement of digestive organs, to divert blood and energy to other parts of the body that need it more. Light changes were due to the dilation of the pupil to allow for more precise vision. The heart racing was due to an increased rate and strength of heart contractions to ensure enough blood and energy is being pumped to vital organs and muscles.
| Descriptor | Marks |
|---|---|
Identifies the sympathetic pathway | 1 |
1 mark for each correct point (any 3 of): neurons originate in the middle region of the spinal cord (thoracic and lumbar); neurons leave spinal cord via ventral root; synapse close to spinal cord with next neuron (postganglionic fibre); release noradrenaline to effect target organ; two motor neurons and one synapse | 3 |
Explains that the responses prepare the body for physical work | 1 |
States that this is the activation of fight or flight responses, protects the body from harm, or acts as lifesaving mechanisms | 1 |
Explains that sweating was because of the activation of sweat glands | 1 |
States that this is to keep the body cool during physical activity | 1 |
Explains that the stomach feeling was due to decreased movement of digestive organs or intestinal arterioles constricting | 1 |
States that this is to divert blood or energy to other parts of the body that need it more | 1 |
Explains that light changes were due to the dilation of the pupil | 1 |
States that this allows for more precise vision or the ability to interpret visual stimuli | 1 |
Explains that the heart racing was due to an increased rate or strength of heart contractions | 1 |
States that this ensures enough blood or energy is being pumped to vital organs or muscles | 1 |
The level of expression in a gene in the bacterium E. coli varies. It depends on the amount of gene product in the bacterial cell, where the level of expression declines as the amount of product increases and vice-versa. This is an example of
transcription.
translation.
positive feedback.
negative feedback.
Reveal Answer
transcription.
Transcription is the process of synthesizing RNA from a DNA template, not the regulatory mechanism described in the prompt.
translation.
Translation is the process of synthesizing proteins from an mRNA template, which does not describe the feedback loop mentioned.
positive feedback.
In positive feedback, an increase in the product would cause an increase in gene expression, amplifying the response rather than reducing it.
negative feedback.
This is a classic example of negative feedback, where the accumulation of a product inhibits the process that creates it, helping the cell maintain homeostasis.
The rate of heat exchange between an animal and its environment could be increased by
the animal standing in the open in a strong wind.
insulating layers of feathers or fur on the animal.
vasoconstriction in the limbs of the animal.
reducing the number of sweat glands in the animal.
Reveal Answer
the animal standing in the open in a strong wind.
Standing in a strong wind increases convective heat transfer, which accelerates the rate of heat exchange between the animal and its environment.
insulating layers of feathers or fur on the animal.
Feathers and fur act as insulation by trapping a layer of air near the body, which decreases the rate of heat exchange.
vasoconstriction in the limbs of the animal.
Vasoconstriction narrows blood vessels near the skin's surface, reducing blood flow and thereby decreasing the rate of heat exchange with the environment.
reducing the number of sweat glands in the animal.
Sweat glands facilitate evaporative cooling; reducing their number would decrease the animal's ability to exchange heat with the environment.
Homeostatic processes involve both nerves and hormones in the maintenance of many bodily functions, such as blood glucose levels.
Define homeostasis and describe how a negative feedback model contributes to the maintenance of bodily functions.
Reveal Answer
Homeostasis is the ability of an organism to maintain a constant internal environment or steady state, despite changes in either internal or external conditions, to maintain optimal functioning of cells.
Negative feedback is activated when internal or external conditions change from optimal conditions. It is when the response counteracts the change, which returns the body to normal.
In the maintenance of bodily functions, a stimulus is a change in the internal or external environment. The receptor detects a change outside of the tolerance limits and produces a nervous or hormonal signal. The control centre receives and processes the signal, then sends a message to the effector. The effector, such as a muscle or gland, carries out the response. The response counteracts the initial stimulus.
Homeostasis
| Descriptor | Marks |
|---|---|
Defines homeostasis as the ability of an organism to maintain a constant internal environment/steady state | 1 |
States that this occurs despite changes in either internal or external conditions | 1 |
Explains that the purpose is to maintain optimal functioning of cells/cell processes/metabolic processes | 1 |
Negative feedback
| Descriptor | Marks |
|---|---|
States that negative feedback is activated when internal or external conditions change from optimal conditions | 1 |
Describes that the response counteracts the change/response reduces stimulus | 1 |
States that it returns the body/body cells to normal | 1 |
Maintenance of bodily functions
| Descriptor | Marks |
|---|---|
Defines a stimulus as a change in the internal/external environment | 1 |
States that the receptor detects a change (outside of the tolerance limits) | 1 |
States that it produces a nervous or hormonal signal | 1 |
States that the control centre/modulator receives the signal/processes signal | 1 |
States that it sends a message to the effector | 1 |
States that the effector/muscle/gland carries out the response | 1 |
States that the response counteracts the initial stimulus/reduces stimulus/has the opposite effect to the initial stimulus | 1 |
Explain the role the adrenal glands play in maintaining blood glucose levels.
Reveal Answer
The adrenal cortex secretes cortisol or glucocorticoids, which stimulates the conversion of glycogen into glucose. It increases the rate that amino acids are removed from muscle cells and taken to the liver, where amino acids are converted into glucose by the liver. It also increases the movement of fatty acids from adipose tissue to muscle cells for use. The adrenal medulla produces adrenaline or noradrenaline, which stimulates the production of lactic acid from glycogen in muscle cells. This lactic acid is then converted to glucose in the liver.
| Descriptor | Marks |
|---|---|
1 mark for each correct point (any 7 of):
| 7 |