Life Processes in Plants – Short Answer Type Questions
CBSE Class 7 — Science
Chapter 10: Life Processes in Plants — 50 Short Answer Questions & Answers (Topic-wise)
Class 7
Science
NCERT
CBSE
Short Answers
Content Bank — Chapter 10 Overview
This set provides concise, exam-focused short answers covering key topics: photosynthesis, leaf anatomy, transport systems (xylem & phloem), transpiration, respiration, modes of nutrition, experiments, adaptations and important definitions.
Topic-wise Short Answer Questions
Topic A — Photosynthesis (Questions 1–10)
- 1. Define photosynthesis.Photosynthesis is the process by which green plants make food (glucose) from carbon dioxide and water using sunlight and chlorophyll.
- 2. Write the balanced chemical equation for photosynthesis.6CO2 + 6H2O + light → C6H12O6 + 6O2.
- 3. Where in the cell does photosynthesis occur?In chloroplasts, which contain the pigment chlorophyll found mainly in leaf mesophyll cells.
- 4. Name three factors that affect the rate of photosynthesis.Light intensity, carbon dioxide concentration, and temperature. Availability of water and chlorophyll amount also matter.
- 5. Why are leaves green?Leaves appear green because chlorophyll absorbs other wavelengths of light and reflects green light.
- 6. How is starch related to photosynthesis?Glucose produced in photosynthesis is often converted into starch for storage in leaves, stems or roots.
- 7. Describe briefly an experiment to show that sunlight is needed for photosynthesis.Keep a potted plant in dark for 48 hours, then expose only part of a leaf to sunlight. Test leaf with iodine — only the exposed part turns blue-black showing starch formation.
- 8. What is the role of carbon dioxide in photosynthesis?Carbon dioxide is a raw material that combines with water using energy to form glucose during photosynthesis.
- 9. Explain why plants are called autotrophs.Plants make their own food (autotrophs) using inorganic materials (CO₂, H₂O) and sunlight, unlike animals that must eat other organisms.
- 10. What is the significance of photosynthesis for life on Earth?Photosynthesis produces oxygen for respiration and forms the base of the food chain by providing organic food for other organisms.
Topic B — Leaf Structure & Function (Questions 11–20)
- 11. Name the layers of a typical leaf from top to bottom.Cuticle, upper epidermis, palisade mesophyll, spongy mesophyll, lower epidermis (with stomata).
- 12. What is the function of the cuticle?The waxy cuticle reduces water loss from the leaf surface.
- 13. Why are palisade cells important?Palisade cells are packed with chloroplasts and are the main site of photosynthesis.
- 14. What are stomata and where are they located?Stomata are small pores mostly on the lower surface of leaves; they allow gas exchange and transpiration.
- 15. How do guard cells control stomata?Guard cells swell and become turgid to open stomata or lose turgor to close them, regulating gas exchange and water loss.
- 16. What is the role of veins in leaves?Veins contain xylem and phloem that transport water, minerals, and food to and from the leaf.
- 17. Explain the difference between palisade and spongy mesophyll.Palisade mesophyll has tightly packed chlorophyll-rich cells for photosynthesis; spongy mesophyll has air spaces for gas exchange.
- 18. How does leaf shape help in photosynthesis?Leaves are typically broad and thin to provide a large surface area for light absorption and efficient gas exchange.
- 19. What is a leaf blade (lamina)?The broad, flat part of the leaf that carries out most photosynthesis.
- 20. Mention one adaptation of leaves in aquatic plants.Many aquatic plants have stomata on the upper surface only to facilitate gas exchange with air above water.
Topic C — Transport of Water & Minerals (Questions 21–30)
- 21. How do roots absorb water from soil?Root hairs increase surface area and absorb water and minerals by osmosis and active transport.
- 22. What is xylem and what does it transport?Xylem is vascular tissue that transports water and dissolved minerals upward from roots to stems and leaves.
- 23. Define transpiration pull.Transpiration pull is the suction force created by water loss from leaves that helps draw water upward through xylem vessels.
- 24. Name two factors that increase transpiration.High temperature and low humidity increase transpiration; wind and bright light also increase it.
- 25. What is root pressure?Root pressure is a push from roots due to active uptake of minerals and water, which can help move water upward slightly.
- 26. How does transpiration help in cooling the plant?Evaporation of water from leaf surfaces removes heat, helping to cool the plant.
- 27. Why is cohesion and adhesion important for water transport?Cohesion (water molecules stick to each other) and adhesion (stick to xylem walls) allow a continuous water column to be pulled up in xylem.
- 28. Give one structural feature of xylem vessels that helps water flow.Xylem vessels are long, tubular and hollow with lignified walls, providing an open conduit for water movement.
- 29. How are minerals transported in plants?Minerals dissolved in water are transported along with water in the xylem from roots to different plant parts.
- 30. Explain briefly how you would demonstrate transpiration experimentally.Place a leafy shoot in a closed transparent plastic bag — water vapour will condense inside indicating transpiration; alternatively use a potometer to measure water uptake.
Topic D — Transport of Food & Translocation (Questions 31–38)
- 31. What is phloem and what is its function?Phloem is vascular tissue that transports organic food (sugars) from leaves to other plant parts (translocation).
- 32. Define translocation.Translocation is the movement of soluble food materials through phloem from source (leaf) to sink (root, fruit).
- 33. How is translocation different from xylem transport?Xylem transport is mainly unidirectional (upwards) and moves water; translocation is bidirectional and moves organic solutes.
- 34. What are companion cells?Companion cells are specialized cells associated with phloem sieve tubes that help in loading and unloading sugars.
- 35. Why is translocation important for growth?Translocation supplies sugars and nutrients to growing and storage tissues required for growth and development.
- 36. Where are sources and sinks in a typical plant?Sources: mature leaves producing food; Sinks: roots, developing fruits, young leaves or storage organs.
- 37. Mention one method to show movement of food in plants.Use labelled carbon (C-14) in CO₂ or use coloured sugar solutions and track movement; for school level, remove a ring of bark to show accumulation above the ring.
- 38. How do phloem tubes differ in structure from xylem vessels?Phloem sieve tubes have living cells with sieve plates and companion cells; xylem vessels are dead, hollow and lignified.
Topic E — Respiration & Excretion (Questions 39–44)
- 39. Define respiration in plants.Respiration is the process of breaking down food (glucose) to release energy for cellular activities.
- 40. Differentiate between photosynthesis and respiration (one line).Photosynthesis stores energy by making food; respiration releases energy by breaking food down.
- 41. What is aerobic respiration?Aerobic respiration uses oxygen to completely break down glucose into carbon dioxide, water and energy.
- 42. When does anaerobic respiration occur in plants?Anaerobic respiration occurs when oxygen is scarce (e.g., waterlogged conditions); it produces ethanol and CO₂ in some organisms like yeast.
- 43. How do plants get rid of excess oxygen produced during photosynthesis?Oxygen diffuses out through stomata or is used for respiration by plant cells.
- 44. Explain briefly how plants excrete wastes.Plants excrete wastes by storing them in leaves (later shed), bark, or in vacuoles; gases may be released through stomata and excess water via transpiration or guttation.
Topic F — Modes of Nutrition & Adaptations (Questions 45–50)
- 45. What are heterotrophic plants? Give an example.Heterotrophic plants obtain food from other organisms; example: Cuscuta (dodder) is parasitic and takes food from host plants.
- 46. What are saprophytes?Saprophytes (like many fungi) obtain nutrients from dead organic matter by secreting digestive enzymes and absorbing nutrients.
- 47. Describe one adaptation of plants in deserts.Desert plants may have reduced leaves or thickened stems to store water and a thick cuticle to reduce water loss (e.g., cactus).
- 48. Why are insectivorous plants like Venus flytrap considered special?They trap insects to obtain nitrogen and other minerals from prey, helping them in nutrient-poor soils.
- 49. What is the function of aerenchyma in aquatic plants?Aerenchyma provides buoyancy and large air spaces for gas exchange in aquatic plants.
- 50. How do deciduous trees manage waste and energy during seasonal changes?Deciduous trees shed leaves in unfavorable seasons to reduce water loss and conserve energy; nutrients are reabsorbed before leaf fall.
Prepared as per NCERT Class 7 Chapter 10 — suitable for classroom handouts, revision notes and short answer practice for CBSE exams.