1
A student observes a plant placed near a window. After a few days, they notice that the stem of the plant is bending towards the window.(a) What is this phenomenon called? [1 mark](b) Which plant hormone is primarily responsible for this movement? [1 mark](c) Explain how this hormone causes the stem to bend towards the light. 3marks
2
A group of students conducted an experiment to demonstrate geotropism. They placed germinated seeds in a box with light coming from one side and gravity acting downwards.(a) Predict the direction of growth of the root and the shoot in this setup. [1 mark](b) Explain the reason behind the observed growth direction for both the root and the shoot. [2 marks](c) If the box is then rotated 180 degrees, how will the roots and shoots respond after a few days? 2marks
3
Assertion (A): Reflex actions are faster than voluntary actions.Reason (R): Reflex actions involve a simpler neural pathway (reflex arc) with fewer neurons.(a) Both A and R are true and R is the correct explanation of A. [1 mark](b) Both A and R are true but R is not the correct explanation of A. [1 mark](c) A is true but R is false. [1 mark](d) A is false but R is true. 1mark
4
A person suddenly touches a hot iron. They immediately withdraw their hand without feeling the pain.(a) Identify the type of response observed in this situation. [1 mark](b) Trace the path of the nerve impulse from the receptor to the effector in this response. [3 marks](c) Name the part of the central nervous system where this response is primarily coordinated. 1mark
5
Read the following passage and answer the questions:The human brain is a complex organ responsible for various functions. It receives information from sensory organs, processes it, and sends out instructions to muscles and glands. The brain is divided into three main parts: fore-brain, mid-brain, and hind-brain, each with specific roles.(a) Which part of the brain is considered the main thinking part and is responsible for interpreting sensory information? [1 mark](b) Identify the part of the hind-brain that controls involuntary actions like blood pressure and vomiting. [1 mark](c) Which part of the hind-brain is responsible for precision of voluntary actions and maintaining posture? [1 mark](d) How is the brain protected from mechanical shocks? 2marks
6
A patient is diagnosed with diabetes due to the underproduction of insulin.(a) Name the gland responsible for producing insulin. [1 mark](b) Explain the role of insulin in the body. [2 marks](c) How does the underproduction of insulin lead to a rise in blood sugar levels? 2marks
7
During a stressful situation, a person's heart rate increases, breathing rate goes up, and blood is diverted from the digestive system to skeletal muscles.(a) Name the hormone responsible for these changes. [1 mark](b) Identify the glands that secrete this hormone. [1 mark](c) Explain the purpose of these physiological changes in preparing the body to face the situation. 3marks
8
A student is studying the structure of a neuron. They observe that it has a cell body, dendrites, and an axon.(a) Where is information acquired by the neuron? [1 mark](b) Through which part does the electrical impulse travel along the neuron? [1 mark](c) What happens at the synapse between two neurons? 2marks
9
Consider a situation where a person is trying to balance on a tightrope.(a) Which part of the brain plays a crucial role in maintaining balance and posture? [1 mark](b) How does this part of the brain achieve this coordination? [2 marks](c) What would happen if this part of the brain was not functioning correctly? 2marks
10
The leaves of a ‘chhui-mui’ plant fold up and droop when touched.(a) What is the stimulus for this rapid movement? [1 mark](b) Explain the mechanism by which the plant cells bring about this movement. [2 marks](c) How does this movement differ from the growth-related movement of a tendril around a support? 2marks
11
Read the following scenario: A boy accidentally stumbles and scrapes his knee. He immediately cries out in pain and withdraws his leg.(a) Identify the type of action observed. [1 mark](b) Explain the role of sensory neurons and motor neurons in this response. [3 marks](c) Where is the synapse located in this reflex arc? 1mark
12
Plants respond to various environmental stimuli by growing in specific directions.(a) Define a 'tropic movement'. [1 mark](b) Give an example of a plant hormone that promotes growth and explain its role. [2 marks](c) Differentiate between positive and negative tropism with an example of each. 2marks
13
Assertion (A): Adrenaline is a hormone that prepares the body for 'fight or flight'.Reason (R): Adrenaline increases heart rate, breathing rate, and diverts blood to muscles.(a) Both A and R are true and R is the correct explanation of A. [1 mark](b) Both A and R are true but R is not the correct explanation of A. [1 mark](c) A is true but R is false. [1 mark](d) A is false but R is true. 1mark
14
A farmer notices that the roots of his crops are growing downwards, away from the sunlight.(a) What is the stimulus in this case? [1 mark](b) Identify the type of tropism exhibited by the roots. [1 mark](c) Explain why this response is advantageous for the plant. 3marks
15
The endocrine system in animals uses chemical signals for coordination.(a) Name one endocrine gland and the hormone it secretes. [1 mark](b) Describe the function of the hormone you named in part (a). [2 marks](c) Explain the importance of precise secretion of hormones in the body. 2marks
16
A student is studying the communication system in plants. They are particularly interested in how plants respond to touch.(a) How do plants communicate information from one cell to another? [1 mark](b) What physical process allows plant cells to change shape for movement? [2 marks](c) Compare the speed of this communication and movement with that in animals. 2marks
17
A person experiences a sudden loss of balance while walking.(a) Which part of the brain is primarily responsible for maintaining balance? [1 mark](b) What could be the reason for the loss of balance? [2 marks](c) How does this part of the brain coordinate to maintain balance? 2marks
18
Read the following statement: "The timing and amount of hormone release are regulated by feedback mechanisms."(a) Explain what a feedback mechanism is in the context of hormone regulation. [2 marks](b) Provide an example of a hormone and its feedback regulation. 3marks
19
When you touch something hot, your hand withdraws automatically.(a) Name the type of response this is. [1 mark](b) Why is this response necessary for survival? [2 marks](c) How does the nervous system ensure such a rapid response? 2marks
20
A child is experiencing stunted growth. A doctor suspects a hormonal imbalance.(a) Name the hormone responsible for regulating growth and the gland that secretes it. [1 mark](b) What would be the effect of deficiency of this hormone during childhood? [2 marks](c) What is the role of the hypothalamus in regulating the secretion of this hormone? 2marks
Answers
1
(a) Phototropism. 1mark(b) Auxin. [1 mark](c) When light falls on the plant from one side, auxin diffuses towards the shady side of the shoot. This increased concentration of auxin on the shady side stimulates the cells to grow longer than the cells on the illuminated side. This differential growth causes the shoot to bend towards the light. [3 marks]
2
(a) The shoot will grow upwards, away from gravity, and towards the light. The root will grow downwards, towards gravity, and away from the light. 1mark(b) Roots exhibit positive geotropism (grow towards gravity) and negative phototropism (grow away from light). Shoots exhibit negative geotropism (grow away from gravity) and positive phototropism (grow towards light). These responses help anchor the plant and obtain resources. [2 marks](c) After rotation, the roots will reorient themselves to grow downwards (towards gravity) and the shoots will reorient themselves to grow upwards (away from gravity) and towards the light source. [2 marks]
3
(a) Both A and R are true and R is the correct explanation of A. [1 mark] (Explanation: Reflex actions bypass conscious brain processing and involve a direct spinal cord pathway (reflex arc), making them faster than voluntary actions which involve higher brain centers.)
4
(a) Reflex action. 1mark(b) Receptors in the skin detect the heat. A sensory neuron transmits the impulse to the spinal cord. In the spinal cord, a relay neuron (or interneuron) connects the sensory neuron to a motor neuron. The motor neuron transmits the impulse to an effector muscle in the arm. The muscle contracts, causing the hand to withdraw. [3 marks](c) Spinal cord. [1 mark]
5
(a) Fore-brain. 1mark(b) Medulla (in the hind-brain). [1 mark](c) Cerebellum (in the hind-brain). [1 mark](d) The brain is protected by being enclosed in a bony box (skull). It is also surrounded by a fluid-filled balloon (meninges and cerebrospinal fluid) which provides shock absorption. [2 marks]
6
(a) Pancreas. 1mark(b) Insulin is a hormone secreted by the pancreas that regulates the level of glucose (sugar) in the blood. It helps cells to take up glucose from the blood, thereby lowering blood sugar levels. [2 marks](c) When insulin is not produced in sufficient amounts, glucose from the digested food cannot be effectively taken up by the body cells. As a result, glucose accumulates in the blood, leading to hyperglycemia (high blood sugar levels). [2 marks]
7
(a) Adrenaline. 1mark(b) Adrenal glands. [1 mark](c) These physiological changes prepare the body to either confront the dangerous situation (fight) or escape from it (flight). Increased heart rate and breathing rate supply more oxygen and nutrients to the muscles. Diversion of blood to skeletal muscles ensures they are ready for quick action. [3 marks]
8
(a) At the dendritic tip of the neuron. 1mark(b) Through the axon. [1 mark](c) At the synapse, the electrical impulse at the end of the axon triggers the release of chemical substances (neurotransmitters). These chemicals cross the gap (synapse) and initiate a similar electrical impulse in the dendrite of the next neuron. [2 marks]
9
(a) Cerebellum. 1mark(b) The cerebellum receives information from the inner ear (which controls balance) and from sensory receptors in the muscles and joints. It processes this information to coordinate muscle movements, maintain posture, and ensure balance during voluntary actions. [2 marks](c) If the cerebellum is not functioning correctly, the person would likely have difficulty maintaining balance, posture, and executing precise voluntary movements, leading to unsteadiness and clumsiness. [2 marks]
10
(a) Touch. 1mark(b) When touched, plant cells at the base of the leaves change their turgor pressure by altering the amount of water they contain. This causes the cells to swell or shrink, leading to the folding and drooping of the leaves. [2 marks](c) The movement in the sensitive plant is rapid and independent of growth, caused by changes in turgor pressure. The movement of a tendril is slow and dependent on growth, where differential growth causes it to coil around a support. [2 marks]
11
(a) Reflex action. 1mark(b) Sensory neurons carry the impulse from the pain receptors in the knee to the spinal cord. In the spinal cord, the sensory neuron connects to a motor neuron (possibly via a relay neuron). The motor neuron then carries the impulse from the spinal cord to the effector muscles in the leg, causing it to withdraw. [3 marks](c) In the spinal cord, at the junction between the sensory neuron and the motor neuron (or relay neuron). [1 mark]
12
(a) A tropic movement is a growth-related movement of a plant in response to a stimulus, where the direction of growth is determined by the direction of the stimulus. 1mark(b) Auxin is a plant hormone that promotes growth. It stimulates cell elongation. In shoots, auxin helps in the growth of stems and leaves. In tendrils, it can cause differential growth, leading to coiling around a support. [2 marks](c) Positive tropism is movement towards the stimulus, e.g., roots showing positive geotropism (growing downwards towards gravity). Negative tropism is movement away from the stimulus, e.g., shoots showing negative geotropism (growing upwards away from gravity). [2 marks]
13
(a) Both A and R are true and R is the correct explanation of A. [1 mark] (Explanation: The physiological changes caused by adrenaline are precisely what prepare the body for fight or flight.)
14
(a) Gravity (Earth's pull). 1mark(b) Negative geotropism. [1 mark](c) Growing downwards into the soil allows the roots to anchor the plant firmly and absorb water and essential minerals from the soil, which are crucial for the plant's survival and growth. [3 marks]
15
(a) Example: Hormone - Thyroxin, Gland - Thyroid gland. 1mark(b) Thyroxin regulates carbohydrate, protein, and fat metabolism in the body, ensuring adequate energy for growth and development. [2 marks](c) Hormones need to be secreted in precise quantities because both under-secretion and over-secretion can lead to various disorders and health problems. For example, deficiency of growth hormone causes dwarfism, while excess causes gigantism. [2 marks]
16
(a) Plants use electrical-chemical means to convey information from cell to cell. 1mark(b) Plant cells change shape by altering the amount of water in them, leading to swelling or shrinking, which results in movement. [2 marks](c) In plants, this communication and movement (especially in response to touch) can be relatively quick but is generally slower than the electrical impulse transmission and muscle action seen in animals, which are designed for rapid responses. [2 marks]
17
(a) Cerebellum. 1mark(b) Possible reasons include a problem with the inner ear (which controls balance), damage to the cerebellum, or issues with sensory input from muscles and joints. [2 marks](c) The cerebellum coordinates signals from the inner ear and sensory receptors to ensure smooth, precise muscle movements and maintain body posture and balance. [2 marks]
18
(a) A feedback mechanism is a regulatory process where the output of a system influences its own operation. In hormone regulation, a change in the body's condition (e.g., blood sugar level) triggers a response (e.g., hormone secretion) that then acts to correct that change, bringing the system back to its normal state. 2marks(b) Example: Insulin regulation. When blood sugar levels rise after a meal, the pancreas detects this and releases insulin. Insulin helps cells take up glucose, lowering blood sugar. As blood sugar levels fall, the pancreas reduces insulin secretion. This is a negative feedback loop. [3 marks]
19
(a) Reflex action. 1mark(b) This rapid withdrawal prevents severe damage to the body, such as burns or deep cuts, from potentially harmful stimuli. [2 marks](c) The nervous system ensures a rapid response through a reflex arc. The sensory impulse bypasses the conscious brain and is directly processed by the spinal cord, which then sends an immediate command to the muscles to contract and withdraw from the stimulus. [2 marks]
20
(a) Hormone: Growth hormone; Gland: Pituitary gland. 1mark(b) Deficiency of growth hormone during childhood leads to dwarfism, characterized by significantly stunted physical growth. [2 marks](c) The hypothalamus plays a role in regulating the release of growth hormone. It secretes releasing hormones that stimulate the pituitary gland to release growth hormone. When growth hormone levels are low, the hypothalamus signals the pituitary to release more. [2 marks]
