1. Food Chains and Food Webs
Unit Seventh Grade

2. Food Chain A food chain shows how each living thing gets its food
Some animals eat plants
Some animals eat other animals
Some animals eat both plants and animals

3. Food Chains Each link in this chain is food for the next link
A food chain always starts with the sun and ends with an animal

4. Food Webs vs. Food Chains

5. Food Chains and Food Webs--- there is a difference!
Food chains show how energy in foods flows from one organism to another.
Few organisms eat just one kind of food!
Food chains are rare!
Food webs show the feeding relationships between organisms in an ecosystem.
Since most organisms eat more than one kind of food, webs are more commonly used!

6. Parts of food chains and Webs
As stated before, a food chain always starts with the sun and ends with an animal.
There are four parts to every food chain
The Sun
Plants (Producers)
Animals (Consumers)
Decomposers

7. The Sun
The Sun is the original source of energy, in the form of light, for the food chain.
Plants (producers) capture this energy to make their food.

8. Producers
Plants are called producers because the are able to make their own food using the Sun’s energy.

9. Consumers
Animals cannot make their own food so they must eat plants and/or other animals.
They are called consumers because they must eat, or consume their energy.

10. Types of Consumers There are 3 kinds of consumers
Herbivores: only eat plants (primary consumers)
Carnivores: only eat other animals
Omnivores: eat both plants and animals

11. Carnivores are broken into two subgroups….
Secondary Consumers
Tertiary Consumers
Carnivores who eat herbivores Example: A snake that eats rabbits
Carnivores who eat other carnivores
Example: Owl eating the snake!

12. Decomposers
Decomposers speed up the decay process in the food chain/web that puts nutrients back into the food chain for the plants to use.
These plants feed the herbivores, which feed the carnivores…..
Examples: bacteria and fungi

13. There are more producers than consumers……
Do you know why?
In a food chain, energy is passed down from one link to another.
When an herbivore eats, only a fraction of that energy that it gets from the plant becomes new body mass.

14. So what happens to the rest of that energy?????
It is used to carry out….
Digestion
Movement
Reproduction
Or it’s just given off as
waste!

15. Review What starts all food chains/webs?
What starts all food chains/webs?
What is the difference between food chains/webs?
What are the four parts of every food chain/web?
Give three examples of a producer
Give three examples of a consumer
What happens to most of the energy in a food chain/web?
Where does this energy go?

16. Therefore-----
When a carnivore eats an herbivore only a small amount of the energy consumed by the herbivore gets passed to the carnivore.

17. And of that small amount of energy ….
Some of it will be “wasted” or “used up” by the carnivore as it carries on its life processes.
A carnivore has to eat A LOT of herbivores to get enough energy to grow!

18. Because of the large amount of energy that is lost at each link ,
the amount of energy that is transferred is lesser and lesser….
In general….
The further up the food chain you go, the less food (and hence, energy) remains available
Most food chains have fewer than five links
A change in size of one population in a food chain will affect other populations

19. The further up you go, the less energy remains available
This is why there are less consumers than producers!

20. Most food chains only have 4-5 links
Why?
There cannot be too many links in a single food chain because
the animals at the end of the chain would not get enough food/energy to stay alive.
Many animals are part of more than one food chain and eat more than one kind of food so they can meet their
energy requirements.
They are part of a food web

21. A change in the size of one population will…
Affect other populations within the same food chain.
For example, if there are too many giraffes, there will not be enough trees and shrubs for them to eat.
This will lead to giraffes dying of starvation.
Fewer giraffes will mean less food for lions
Lions will die of starvation
But….
With less giraffes to eat trees and shrubs, the tree/shrub numbers will grow
And, if there are less lions to eat the giraffes, the giraffe population will have time to multiply again.
ISN’T IT GREAT HOW NATURE WILL TAKE CARE OF ITSELF????

22. Quick Write Use your notes to complete the quick write.
All terms must be used and underlined.
Use at least 3 evidence-based terms in your writing.
If you run out of space on the front, there is this mystical place called the other side of the paper. Visit it!
Draw a picture of a food web when you are finished writing
EVIDENCE-BASED TERMS Because … According to my notes… Mrs. Belaski said … For example … For instance … In my notes, I noticed …

23. Food Web Creation http://www.vtaide.com/png/foodchains.htm
We will be creating a food web as a class.
Remember food web/chain “rules”
Starts with the sun, ends with an animal
Your choices must make sense
I will be using the sticks to call on students