Science and Technology Class 9 Important Questions Chapter 15 Maharashtra Board

Life Processes in Living Organisms

Short Questions

1. How does root pressure contribute to water movement in plants?

• It pushes water and minerals into xylem, forming a water column.

2. Why is transpiration more effective during the day?

• Stomata open in sunlight, increasing water vapor release.

3. What role does ATP play in phloem transport?

• ATP provides energy to move food like sucrose through phloem.

4. How does the concentration gradient affect root absorption?

• It drives water and minerals into root cells from soil.

5. Why is transpiration pull stronger in tall trees?

• Greater evaporation from leaves creates stronger suction.

6. How do guard cells regulate transpiration?

• They control stomata opening by changing shape with water content.

7. What makes translocation an active process?

• It requires ATP to transport food against concentration gradients.

8. Why do plants store waste in vacuoles?

• To isolate harmful substances before they fall off as leaves or bark.

9. How do raphides function in plant defense?

• Their needle-like structure irritates herbivores, deterring them.

10. Why is resin stored in old xylem?

• It safely deposits waste without affecting active plant tissues.

11. How does the nephron ensure selective reabsorption?

• It reabsorbs useful substances like water while leaving wastes.

12. Why is the urinary bladder under nervous control?

• Nerves allow voluntary control over urination in adults.

13. How does dialysis mimic kidney function?

• It filters nitrogenous wastes from blood using a machine.

14. Why is less urine produced in summer?

• Increased sweating reduces water available for urine formation.

15. How does the skin assist in human excretion?

• It excretes water and salts through sweat.

16. Why is coordination essential for homeostasis?

• It maintains balance by aligning body responses to changes.

17. How do electrochemical impulses aid plant coordination?

• They transmit signals to trigger movements like leaf folding.

18. Why is phototropism critical for plant survival?

• It ensures leaves face sunlight for maximum photosynthesis.

19. How does gravitropism benefit root growth?

• It directs roots downward to access water and nutrients.

20. What triggers chemotropic movement in plants?

• Chemical stimuli, like ovule signals, guide pollen tube growth.

21. Why do touch-me-not leaves fold on contact?

• Water content changes in cells cause rapid movement.

22. How does auxin influence plant growth?

• It promotes cell enlargement in shoots toward light.

23. What makes neurons unique in signal transmission?

• They conduct electrochemical impulses across long distances.

24. Why is the synapse critical in nerve function?

• It allows impulse transfer between neurons via neurotransmitters.

25. How does the cerebrum’s structure enhance its function?

• Convolutions increase surface area for more neurons.

26. Why is the medulla oblongata vital for survival?

• It controls essential functions like breathing and heartbeat.

27. How do sensory neurons differ from motor neurons?

• Sensory neurons carry impulses to the brain; motor neurons signal effectors.

28. What role does cerebrospinal fluid play in the brain?

• It cushions the brain and supplies nutrients.

29. Why are reflex actions faster than conscious responses?

• They bypass the brain, using the spinal cord for quick action.

30. How does the autonomic nervous system function?

• It controls involuntary organs like the heart without conscious effort.

Long Questions

1. How does root pressure facilitate water transport in plants?

• Root pressure, created by turgid root cells absorbing water and minerals, pushes them into the xylem, forming a water column. This helps small plants move water upward, as seen when stained solution travels up a balsam stem.

2. What is the significance of transpiration in plants?

• Transpiration releases water vapor through stomata, creating a pull that draws water from roots to leaves. It cools the plant and aids nutrient distribution, like in maize releasing thousands of liters daily.

3. How does phloem transport food in plants?

• Phloem moves food, like sucrose, from leaves to other parts using ATP energy against concentration gradients. This supports growth, as sugar reaches buds during flowering.

4. How do plants manage waste without excretory organs?

• Plants store waste in vacuoles of leaves or bark, which fall off, or release gases via stomata. Some wastes, like resin, are deposited in xylem, unlike human kidney-based excretion.

5. What are raphides, and how do they affect humans?

• Raphides are needle-shaped calcium oxalate crystals in plants like arum, causing skin irritation when touched. They defend plants but can prickle human skin during handling.

6. How does the human kidney form urine?

• Kidneys filter blood in nephrons, where the glomerulus separates wastes like urea, forming urine. Useful substances are reabsorbed, and urine is stored in the bladder for expulsion.

7. What is the purpose of dialysis in kidney failure?

• Dialysis filters nitrogenous wastes from blood using a machine when kidneys fail, preventing toxin buildup. Purified blood is returned, as done for 500 ml at a time.

8. Why is coordination crucial for organism survival?

• Coordination ensures body systems work together to respond to changes, maintaining balance. For example, nerves coordinate muscle movement to avoid a hot surface.

9. What are tropic movements, and why are they important?

• Tropic movements are growth responses to stimuli, like sunflowers bending toward light for photosynthesis. They help plants optimize growth and resource use in their environment.

10. How do growth-irrelevant movements function in plants?

• Growth-irrelevant movements, like touch-me-not leaves folding when touched, occur due to water content changes. Venus flytraps closing on insects show rapid, non-growth responses.

11. How do neurons contribute to human coordination?

• Neurons transmit electrochemical impulses from sensory organs to muscles or glands, enabling quick responses. For example, they signal hand withdrawal from a hot object.

12. What is the role of the human brain’s cerebrum?

• The cerebrum, with convolutions for more neurons, controls thinking, speech, and memory. It manages complex tasks, like solving math or writing, unlike other brain parts.

13. How does the cerebellum differ from the medulla oblongata?

• The cerebellum ensures balance and coordination, like during walking, with shallow grooves. The medulla oblongata controls vital functions, like breathing, and connects to the spinal cord.

14. What is a reflex action, and how does it protect the body?

• Reflex action is an involuntary response to stimuli, like blinking at approaching objects, bypassing the brain. It protects by enabling rapid reactions via the spinal cord.

15. How does the autonomic nervous system regulate body functions?

• The autonomic nervous system controls involuntary organs, like the heart and lungs, without conscious effort. It ensures steady heartbeats and breathing, maintaining body functions.