Photosynthesis and food webs
Photosynthesis as a word equation, and how food webs share the Sun’s energy. Read one part at a time and tap “I know this”. Then test yourself in the quiz.
Know it already? Jump straight to the quiz
The word equation
carbon dioxide + water → sugar + oxygen
The plant takes in water through its roots and carbon dioxide through its leaves. The green chlorophyll in the chloroplasts captures light energy and builds sugar. Oxygen is made along with the sugar: a by-product. Without light there is no energy, so in the dark photosynthesis stops.
- In autumn the chlorophyll breaks down, and the leaves change colour.
- Large forests absorb lots of carbon dioxide: important for the climate.
- In a crowded forest plants compete for light, water and nutrients.
Where does the sugar go?
The plant uses some of the sugar straight away for energy. It turns the rest into starch and stores it in its leaves, stems, roots, fruits and seeds. That is why potatoes, mealies, rice and bread are full of starch. Food from animals, such as meat and eggs, has no starch: only plants make it.
- The oxygen leaves through tiny holes in the leaves into the air. Animals and people need it to breathe.
- Drop iodine on a slice of potato: it turns blue-black, because the potato has stored starch.
Food webs
| Role | What it does | Example |
|---|---|---|
| Producer | Makes its own food with sunlight | Grass, trees, ferns |
| Herbivore (plant eater) | Eats only plants | Bushbuck |
| Carnivore (meat eater) | Eats other animals | Forest buzzard |
| Omnivore (eats everything) | Eats plants and animals | Baboon, human |
| Decomposer | Breaks down dead plants and animals; the nutrients go back into the soil | Fungi, bacteria (micro-organisms) |
- A food chain shows one path of food: grass → locust → bird. The arrow means “is eaten by” and shows the direction the energy flows, from the food to the eater.
- A food web is many food chains joined together. A predator hunts and eats other animals, its prey.
- All the energy starts with the Sun. If all the plants disappeared, all the animals would eventually die.
- A top predator becomes extinct? Its prey increase, and the web goes off balance.
- A fungus on a dead log is a decomposer.
- Poison builds up higher in the web: biomagnification.
Remember this and test yourself
- Carbon dioxide + water → sugar + oxygen (with light energy).
- Chlorophyll captures the light; in a plant cell photosynthesis happens in the chloroplasts.
- Oxygen is a by-product. Day and night the plant releases energy from its sugar by respiration; at night there is only respiration.
- The first consumer is a herbivore; energy is lost at each level.
- The more links in a web, the better the ecosystem survives: other species fill a gap.
Write these points in your book. Read them again the night before the test.
The plant eats light: CO₂ + water in, sugar + O₂ out. That gives us the oxygen we breathe. But plants also respire day and night, just like us.
Important words
First say what the word means, then turn the card over.
Match column A to column B
Tap a word in column A, then its meaning in column B. You can also start in column B.
True or false?
Read the question and the answer. Is the answer right? Tap True or False.
Now the real quiz!
The quiz has many more questions on this topic. Every question shows straight away whether you are right and explains why.
Take the quiz: Photosynthesis and food webs- Read one part together and ask your child to tell it back in their own words.
- The ticks (“I know this”) are saved on this device only. We never ask for names or emails.
Follows CAPS for Grade 6 Natural Sciences and Technology. Always check your teacher’s notes and textbook too.