1. Food chains and Food webs
Objective: To understand where energy comes from and how it flows from organism to organism.

2. What would happen if?
The sun disappeared

3. What would happen if?
There were no insects?

4. What would happen if?
There were no rats or mice?

5. What would happen if?
We could grow no plants

6. All living things need energy to survive
The flow of energy from organism to organism is called a FOOD CHAIN

7. A food chain is:
A simple relationship that shows energy flow from one organism to another
It is a flow chart
All food chains start with the sun
Plants get their energy from the sun to grow,
Animals get their energy by consuming plants
These relationships are actually quite complex, and they are shown in FOOD WEBS

8. Food chains and food webs

9. Producers consumers and decomposers
Different organisms have different roles in the food chain
Producers
Consumers
Decomposers
FOOD WEBS start with the sun
Sun gives out light energy
Plants uses energy to make their food

10. Producers
Plants are called producers because they can make their own food
All organisms are dependent on the oxygen that plants produce

11. Producers (continued)
Plants trap sunlight in their leaves and use chlorophyll to help them use sunlight to make carbohydrates.
This is called photosynthesis:

12. Consumers
Animals are called consumers because they are unable to make their own food and must eat plants or other animals
There are 3 types of consumers:
Herbivores
Carnivores
Omnivores

13. Types of consumers
Herbivores: eat only plants

14. Types of consumers
Carnivores: eat only meat

15. Types of consumers
Omnivores eat both plants and animals

16. Decomposers:
Decomposers get the energy they need as they break down dead matter
If plants or animals die without being eaten, the body is broken down by bacteria and fungi

17. Food Chain

18. Energy flow through a food web
Not all energy is passed on in the web
Some is lost as heat, or used by the organism that consumes for growth and movement
Energy is also lost in the cellular reactions each organism carries out to survive
As you move up the web, there is less energy to be passed on
This means fewer organisms at each level

19. Biomass pyramid
If one organism is removed, another must replace it or it will upset the balance.

20. Your task Explain why all food webs start with the sun
In you workbook, answer questions 1 – 4 on page 237 of your textbook