What it shows
Energy passes from the Sun to plants and then to animals that eat them. The spinner shows who eats whom and why the chain starts with a producer.
The science
Green plants are producers; they make food by photosynthesis using sunlight. Herbivores eat plants, carnivores eat herbivores and decomposers break down dead matter. Each step passes on only about 10 percent of the energy, so food chains are short. Many chains join to form a food web.
Materials
Cost: under Rs 50. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.
- Four paper plates, one for the top and three for the bottom wheels
- A split pin or paper fastener
- Markers and pictures cut from old magazines
- Glue
- Scissors (adult help)
- A strip of card as the pointer
Safety
For this project: An adult must cut the window in the plate and push the split pin through.
Never use mains electricity: power models with cells, batteries or a low-voltage adapter. Sharp and hot tools, flames and lab chemicals need an adult or your teacher beside you. Keep magnets, button cells and small parts away from young children, and wash your hands after making.
Step by step
8 steps. Do them in order, and test each part before you go on to the next. Write what you notice in a notebook as you go.
On the top plate, cut out a pie slice window one eighth in size.
On the first bottom plate, divide it into eight sections and draw one organism in each, putting grass, grasshopper, frog, snake and eagle in order in the first five sections.
Fix the top plate over the bottom with a split pin so it can turn.
Write the heading Who eats whom at the top.
Turn the wheel one section at a time to show the grass, grasshopper, frog, snake, eagle chain in order.
Draw arrows from eaten to eater on a card.
Make the second and third bottom plates for a pond chain and a forest chain, and swap them under the same top plate.
Draw a food web linking the chains together.
What you should see
A spinner that shows any food chain by turning, and a web combining three chains.
Viva questions
A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.
01Why do all food chains start with plants?
Plants make food from sunlight.
02What do the arrows show?
The direction of energy flow from eaten to eater.
03What is a decomposer?
An organism like fungi that breaks down dead matter.
04Why are food chains short?
Only about 10 percent of energy passes on at each step.
Take it further
Draw an energy pyramid with 1000 units at the base and calculate energy at each level.
Change one thing, measure what happens, and add a table or chart of your readings: that is what turns a model into your own investigation.
Free ebooks for this project
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