Organisms Respond to Changes Practice Questions
A-Levels · A-Level Biology · 144 free MCQs with instant results and detailed explanations.
144
Total
41
Easy
73
Medium
30
Hard
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Sample Questions from Organisms Respond to Changes
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Q1
Easy
What is the primary function of the nervous system in organisms?
A.
To process information and coordinate responses
B.
To produce hormones that regulate metabolism
C.
To transport nutrients throughout the body
D.
To provide structural support to cells
Show Answer & Explanation
Correct Answer: A
The primary function of the nervous system is to process information and coordinate responses to stimuli, allowing organisms to react to their environment effectively.
Q2
Easy
Which of the following is an example of a reflex action?
A.
Deciding to move your hand away from a hot surface
B.
Pulling your hand back after touching a sharp object
C.
Choosing to sit down after feeling tired
D.
Stretching when you wake up in the morning
Show Answer & Explanation
Correct Answer: B
A reflex action is an automatic and rapid response to a stimulus, such as pulling your hand back after touching a sharp object, which occurs without conscious thought.
Q3
Easy
What is the primary function of the nervous system in organisms?
A.
To transport oxygen and nutrients
B.
To coordinate responses to stimuli
C.
To produce hormones
D.
To facilitate digestion
Show Answer & Explanation
Correct Answer: B
The primary function of the nervous system is to coordinate responses to stimuli by transmitting signals between different parts of the body. This allows organisms to react appropriately to their environment.
Q4
Medium
Which of the following best describes the role of the hypothalamus in thermoregulation?
A.
It directly produces hormones that increase body temperature.
B.
It acts as the control center for regulating body temperature.
C.
It generates heat through shivering thermogenesis.
D.
It measures external temperatures to influence behavior.
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Correct Answer: B
The hypothalamus serves as the control center for thermoregulation by receiving input from thermoreceptors and initiating responses to maintain body temperature.
Q5
Medium
In plants, which hormone is primarily responsible for promoting cell elongation?
A.
Gibberellins
B.
Auxins
C.
Cytokinins
D.
Ethylene
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Correct Answer: B
Auxins are plant hormones that stimulate cell elongation, particularly in stems and roots, facilitating growth in response to environmental stimuli.
Q6
Medium
What is the expected response of a mammal's body when exposed to extreme cold?
A.
Vasodilation and increased sweating.
B.
Vasoconstriction and shivering.
C.
Increased heart rate and vasodilation.
D.
Decreased metabolic rate and increased heat production.
Show Answer & Explanation
Correct Answer: B
In response to extreme cold, mammals exhibit vasoconstriction (to reduce heat loss) and shivering (to generate heat), which are essential for maintaining body temperature.
Q7
Medium
Which of the following accurately describes the role of neurotransmitters in synaptic transmission?
A.
They directly generate action potentials in the presynaptic neuron.
B.
They are released from the postsynaptic neuron to inhibit the presynaptic neuron.
C.
They facilitate communication between neurons by binding to receptors on the postsynaptic neuron.
D.
They are responsible for the enzymatic breakdown of the neurotransmitter.
Show Answer & Explanation
Correct Answer: C
Neurotransmitters are released from the presynaptic neuron and bind to receptors on the postsynaptic neuron, facilitating the transmission of signals across the synapse.
Q8
Hard
Which of the following accurately describes the role of the hypothalamus in the regulation of body temperature in mammals?
A.
It detects changes in blood temperature and initiates responses to dissipate or conserve heat.
B.
It directly produces heat through metabolic processes to maintain temperature.
C.
It solely regulates temperature by controlling the blood flow to the extremities.
D.
It has no significant role in thermoregulation compared to the skin.
Show Answer & Explanation
Correct Answer: A
The hypothalamus functions as a thermoregulator by detecting changes in the body's blood temperature and triggering appropriate physiological responses such as sweating or shivering to maintain homeostasis.
Q9
Hard
In a study of phototropism, a plant is exposed to unilateral light. Which of the following hormonal changes is primarily responsible for the bending of the plant towards the light source?
A.
Increased levels of cytokinins on the light-exposed side.
B.
Increased auxin concentration on the dark side of the plant.
C.
Decreased gibberellins on the light-exposed side.
D.
Increased ethylene production on the dark side.
Show Answer & Explanation
Correct Answer: B
When a plant experiences unilateral light, auxin accumulates on the shaded side, promoting cell elongation and causing the plant to bend towards the light source, which is a key mechanism in phototropism.
Q10
Hard
Which of the following signaling molecules is primarily responsible for mediating the response of plants to light direction (phototropism)?
A.
Auxin
B.
Gibberellin
C.
Cytokinin
D.
Ethylene
Show Answer & Explanation
Correct Answer: A
Auxin is a plant hormone that promotes cell elongation in response to light. It accumulates on the shaded side of a plant, causing the plant to bend towards the light source. This process is known as phototropism, making auxin the key signaling molecule in this response.
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Organisms Respond to Changes — A-Levels A-Level Biology Practice Questions Online
This page contains 144 practice MCQs for the chapter Organisms Respond to Changes in A-Levels A-Level Biology. The questions are organized by difficulty — 41 easy, 73 medium, 30 hard — so you can choose the right level for your preparation.
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