Green plants make their own food through photosynthesis. This is why they are called autotrophs (producers). Photosynthesis is one of the most frequently examined topics in WAEC Biology.
What is Photosynthesis?
Photosynthesis is the process by which green plants manufacture carbohydrates (glucose) from carbon dioxide and water, using sunlight energy trapped by chlorophyll.
Conditions and Raw Materials
- Raw materials: carbon dioxide (from the air) and water (from the soil).
- Conditions: sunlight (energy) and chlorophyll (in the chloroplasts).
- Products: glucose (used or stored as starch) and oxygen (released into the air).
Structure of the Leaf (Adaptations for Photosynthesis)
| Leaf feature | Adaptation |
|---|---|
| Broad, flat shape | Large surface area to absorb sunlight |
| Thin structure | Short distance for gases to diffuse |
| Stomata (pores) | Allow carbon dioxide in and oxygen out |
| Chloroplasts in palisade cells | Contain chlorophyll to trap light energy |
| Network of veins (xylem) | Deliver water to the leaf |
Importance of Photosynthesis
- Produces food for plants (and, indirectly, all animals).
- Releases oxygen needed for respiration by all living things.
- Removes carbon dioxide from the atmosphere.
Test yourself: Name the four conditions and materials needed for photosynthesis. Answer: carbon dioxide, water, sunlight and chlorophyll.
Summary
Photosynthesis converts carbon dioxide and water into glucose and oxygen, using sunlight trapped by chlorophyll. The leaf is specially adapted for this process, and photosynthesis is essential for life on Earth as it produces food and oxygen.
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