Control and Coordination in Living Organisms – Long Answer Questions
Medium Level (Application & Explanation)
Q1. Why do living organisms need both control and coordination? Explain with examples from daily life.
Answer:
Living organisms face constant changes in their environment, such as light, temperature, or threats. To survive, they must sense these changes and respond quickly and properly. Control helps manage or direct these activities, while coordination ensures all parts of the body work together. For example, when we touch a hot object, nerves send a signal to the brain, which tells our muscles to move the hand away. Similarly, plants bend towards sunlight, showing they coordinate growth for photosynthesis. Without control and coordination, organisms would not be able to respond to changes, maintain internal stability, or perform activities like moving, hunting, or growing.
Q2. Describe how the nervous system in animals carries out control and coordination.
Answer:
The nervous system uses specialized cells called neurons to carry electrical messages throughout the body. It includes the brain, spinal cord, and nerves. When a sensory organ (like the skin) detects a stimulus, it sends a signal through nerves to the brain or spinal cord. The brain processes this information and sends a response message to muscles or glands via motor nerves. For example, if you step on something sharp, a signal goes to your spinal cord, and a response is immediately sent to lift your foot (a reflex action). This ensures quick, accurate, and targeted responses to the environment.
Q3. In what ways do plants control and coordinate their responses if they do not have a nervous system?
Answer:
Plants lack a nervous system, so they use chemical coordination. They release chemicals called plant hormones or phytohormones like auxins, gibberellins, cytokinins, abscisic acid, and ethylene. These hormones help control processes like growth direction, flowering, fruit ripening, and falling of leaves. For example, auxins cause bending towards light (phototropism), and abscisic acid makes leaves fall off in autumn. Plant responses are generally slower compared to animals but are very important for adapting to their environment.
Q4. How do the nervous and endocrine systems work together to control and coordinate activities in humans? Give examples.
Answer:
The nervous system provides quick and brief responses using electrical signals, while the endocrine system uses hormones for slow but long-lasting effects. Sometimes, both systems work together. For example, when you get scared, the nervous system senses danger and sends signals to the adrenal glands (part of the endocrine system) to release adrenaline. This hormone increases heartbeat and energy, preparing the body to deal with the situation (fight or flight response). Another example is eating food: the sight and smell trigger salivation (nervous control), while hormones like insulin manage blood sugar (endocrine control).
Q5. Why are reflex actions important in animals? Describe the pathway of a reflex action.
Answer:
Reflex actions are quick, automatic responses to certain stimuli, protecting the body from harm. They happen without thinking because the signal does not first go to the brain. The pathway is called the reflex arc. First, a sensory receptor detects a stimulus (like a pinprick). The message goes by a sensory neuron to the spinal cord. In the spinal cord, an immediate response is generated and sent by a motor neuron to a muscle or gland, making it act at once (like withdrawing your hand). Reflexes help in survival by preventing injuries and enabling fast reactions.
High Complexity (Analysis & Scenario-Based)
Q6. Imagine you are running a race. Describe how your body’s control and coordination systems help you during the race.
Answer:
During a race, your nervous system sends signals from your brain to coordinate the movement of muscles, allowing you to run smoothly. Your eyes and ears help you balance and avoid obstacles. As you need more energy, the endocrine system releases hormones like adrenaline to increase heart rate and provide extra glucose for muscles. Your breathing also speeds up, controlled by the brain, to supply more oxygen. Sweat glands are activated to cool your body. All these activities are coordinated so you can run efficiently and respond to the environment, showing the importance of both fast (nervous) and slow (hormonal) controls.
Q7. Analyze how a plant kept near a window bends towards sunlight. Name the hormone involved and explain the process.
Answer:
This bending towards sunlight is called phototropism. When sunlight comes more from one direction, the hormone auxin moves to the shady side of the stem. Auxin makes cells on that side grow faster, causing the stem to bend toward the light. This allows the plant to get more sunlight for photosynthesis. The process happens slowly and without a nervous system because plants use chemical coordination through hormones. This shows how even simple organisms adapt to their environment using internal control mechanisms.
Q8. Suppose a child eats sweet food. Outline the sequence of events involving both nervous and endocrine control leading to proper digestion of sugars.
Answer:
When the child sees and smells sweet food, the nervous system sends signals to the salivary glands to start making saliva. As food enters the mouth and then the stomach, digestive enzymes start working. When the sugars are absorbed into the blood, blood sugar levels rise. The endocrine system (pancreas) senses this and releases insulin hormone. Insulin tells cells to absorb the sugar, lowering blood sugar levels. Thus, the body coordinates quick responses (saliva production) with slower hormonal responses (glucose absorption) to digest and use the sugar properly.
Q9. Compare and contrast how animals and plants respond to stimuli using examples of (i) escaping a predator and (ii) growing towards light.
Answer:
(i) Escaping a predator: In animals, special sense organs (like eyes, ears) detect danger and the nervous system sends immediate signals to muscles for running or hiding. Hormones like adrenaline help increase energy for escape. In contrast, plants cannot run from danger but may develop thorns or chemicals to discourage herbivores, using slow chemical responses.
(ii) Growing towards light: Animals can move towards or away from light using their nervous system. Plants, lacking a nervous system, use hormones like auxin to grow towards light (phototropism). Animal responses are quick and involve movement, while plant responses are slow and involve growth changes.
Q10. A person sweats while running in sunlight. Explain the role of control and coordination here, and why this response is important for survival.
Answer:
While running in sunlight, body temperature rises. Thermoreceptors in the skin detect this increase. The nervous system sends signals to the part of the brain called the hypothalamus, which directs sweat glands to produce sweat. Sweating cools the body as water evaporates from the skin. The endocrine system may also release hormones to balance water and salt in the body. This coordinated response prevents overheating and keeps the body working properly, which is vital for survival, especially during physical activity in hot conditions.