Chapter Overview
Plants obtain matter and energy, transport materials and exchange gases. Leaves, roots, stems and specialised tissues cooperate in photosynthesis, respiration and growth.
The chapter follows an enquiry-based approach: observe carefully, distinguish evidence from explanation, use appropriate units and communicate conclusions honestly.
Learning Objectives
After studying this chapter, you should be able to:
- explain photosynthesis in clear scientific language;
- explain respiration in clear scientific language;
- explain transport tissues in clear scientific language;
- explain transpiration in clear scientific language;
- connect scientific ideas with familiar situations;
- plan or evaluate a safe and fair investigation.
Key Concepts
| Concept | Explanation | |---|---| | Photosynthesis | Green plants use light energy to make carbohydrates from carbon dioxide and water, releasing oxygen. | | Respiration | Plant cells, like animal cells, release energy from food through respiration throughout day and night. | | Transport tissues | Xylem carries water and minerals mainly upward; phloem transports sugars from sources to places where they are used or stored. | | Transpiration | Water vapour leaves mainly through stomata. This contributes to water movement and cooling but must be regulated. |
Detailed Explanation
Photosynthesis
Green plants use light energy to make carbohydrates from carbon dioxide and water, releasing oxygen.
Respiration
Plant cells, like animal cells, release energy from food through respiration throughout day and night.
Transport tissues
Xylem carries water and minerals mainly upward; phloem transports sugars from sources to places where they are used or stored.
Transpiration
Water vapour leaves mainly through stomata. This contributes to water movement and cooling but must be regulated.
A scientific statement should be supported by observations, measurements or a tested explanation. Record unexpected results instead of hiding them.
Investigation
Cover a leafy twig with a clear dry bag and a second bag over a bare twig as a comparison. Observe droplets after some time without detaching or harming the plant.
For a fair test, identify what is changed, what is measured, and which important conditions are kept the same. Record results before interpreting them.
Important Definitions
- Photosynthesis: Green plants use light energy to make carbohydrates from carbon dioxide and water, releasing oxygen.
- Respiration: Plant cells, like animal cells, release energy from food through respiration throughout day and night.
- Transport tissues: Xylem carries water and minerals mainly upward; phloem transports sugars from sources to places where they are used or stored.
- Transpiration: Water vapour leaves mainly through stomata. This contributes to water movement and cooling but must be regulated.
Use precise terms, labelled diagrams where relevant, and complete cause-and-effect statements. A correct scientific reason is more useful than a one-word answer.
Common Mistakes
- Saying plants respire only at night.
- Assuming plants obtain food directly from soil.
- Confusing xylem with phloem.
Quick Revision
- Photosynthesis: Green plants use light energy to make carbohydrates from carbon dioxide and water, releasing oxygen.
- Respiration: Plant cells, like animal cells, release energy from food through respiration throughout day and night.
- Transport tissues: Xylem carries water and minerals mainly upward; phloem transports sugars from sources to places where they are used or stored.
- Transpiration: Water vapour leaves mainly through stomata.
Practice Questions
- Name the raw materials for photosynthesis.
- What does xylem transport?
- What does phloem transport?
- What are stomata?
Answers and Explanations
- Carbon dioxide and water; light energy and chlorophyll are necessary conditions.
- Water and dissolved minerals.
- Sugars and other organic substances.
- Tiny pores, mainly on leaves, involved in gas exchange and transpiration.
Apply Your Learning
Find one example of this chapter’s science in your home, school or neighbourhood. Describe what you observe, propose an explanation, and state what additional evidence would test that explanation.