1. Energy Flow in Ecosystems
3.4

2. Energy Flow
When an animal eats a plant, energy is transferred from plant to animal
The same thing happens when an animal eats another animal
The transfer of energy through an ecosystem can be traced
This helps scientists see how organisms are connected and how much energy is transferred

3. Food Chains Show how organisms in an ecosystem get their food
Each organism is a link in the chain and provides food for the next link
Always starts with a producer
Always ends with a consumer
Example:

4. Grasslands of Africa pg. 96
Acacia trees  producer
As producers, the trees make their own food using sunlight
Giraffes  primary consumer
They eat the leaves and get some of the energy stored in them
Lions  secondary consumer
Lions feed on giraffes and get the energy stored in their cells

5. Food Webs Most organisms are a part of more than one food chain
This network of feeding relationships is called a food web
Eating many different foods can help a consumer make sure it can find enough food
Pg. 97

6. Trophic Levels Feeding level in a food chain or web
Producers make up the first trophic level
Green plants in a grassland ecosystem
Algae in an ocean ecosystem
In few ecosystems, bacteria form the first level

7. Primary, Secondary, and Tertiary
The second trophic level is made up of herbivores (primary consumers)
The third trophic level is made up of carnivores (secondary consumers)
These feed on primary consumers
In some food chains, there is a fourth or fifth level of consumers (tertiary consumers)
These consumers eat other consumers

8. Energy Pyramids
Which are there more of: producers or consumers? _________________
Trophic levels form a pyramid because there are many more producers than primary consumers
Producers form the bottom of the pyramid
There are more primary consumers than secondary consumers

9. Think about it this way…
A field of grass can only support a certain number of rabbits
The number of rabbits can only support a smaller number of bobcats
The bobcats can only support an even smaller number of cougars

10. Energy Transfer pg. 99
An energy pyramid shows the amount of energy available at each trophic level
Each time energy is transferred, about 90% is lost
Some is lost to heat and escapes into the atmosphere
Only 10% gets stored in the consumer
As you move up the pyramid, less food energy is available

11. The pyramid break down
The first trophic level is the largest and has the most energy
Each level above it has less energy and fewer species
The top level (tertiary) has the smallest amount of energy
This is why there are more small animals than large animals in an ecosystem
Food chains only have 4-5 links

12. Vocabulary Food Chain Food Web Trophic Level Primary Consumer
Secondary Consumer
Tertiary Consumer