1. Food Webs
We will examine the components of an ecosystem in order to analyze and construct food webs.

2. The Source of All Energy?

3. Anatomy of a Food Chain
The source of energy for almost all food chains is the sun
The first organism in every food chain is an autotroph or producer.

4. The Characters
A PRODUCER is an organism that can make it’s own food (AUTOTROPH).

5. Organisms that eat, or consume, the producers or other animals are called CONSUMERS.

6. When organisms die…
Decomposers feed off of dead and decaying matter.

7. Niche An organism’s niche is the role that it plays in an ecosystem.
Includes:
The type of food it eats
How it gets its food
Other organisms that use it for food
Examples:
Carnivore
Predator
Consumer

8. Energy Flow Energy flows in one direction through an ecosystem.
consumer
sun
producer

9. The Food Chain
Energy flow through an ecosystem can be represented by a food chain.
Arrows show the direction of energy flow.

10. In reality, it’s not that simple…

11. The reality is called a “Food Web”
A food web shows the complex interactions between all of the organisms in an ecosystem; it usually consists of several food chains.

12. Types of Consumers
The first, or primary consumer, in every food chain eats the producers.
It would be an herbivore (eats plants only) or an omnivore (eats plants and animals).

13. Types of Consumers
The next, or secondary consumer, eats the primary consumers.
These would be carnivores (eats meat only) or omnivores.
We might also call them predators.

14. Types of Consumers
The chain continues with tertiary consumers, who eat the secondary consumers, etc.

15. Working on the Food Chain

16. Pyramids TROPHIC LEVELS are feeding levels.
Food webs can be represented by a pyramid, with the producers forming the base, because the most energy is stored at that level.

17. To feed 1 human… Fish Frog Grasshopper Grass Pyramid of Numbers Man
Energy Flow
Grasshopper
Grass
Pyramid of Numbers

18. Energy Flow Energy Pyramid H E A T Producers Primary consumers
Tertiary consumers
Secondary consumers
Primary consumers
Producers
Energy Flow
H E A T

19. The RULE OF 10
As energy flows through an ecosystem, only ~10% of stored energy gets passed from one level to the next. The rest returns to the environment as heat.
0.001%
0.01%
0.1% 1%
10%
100%

20. Everything decreases! Biomass (dry weight) decreases Energy decreases
Numbers decrease