1. Interdependence NOTES
When one tugs at a single thing in nature, he finds it attached to the rest of the world.
-- John Muir

2. REVIEW: Producers or autotrophs make their own food (photosynthesis!)
Example: phytoplankton, oak tree, grass
Consumers or heterotrophs must eat to gain energy
Primary consumers eat producers
Examples: Deer, crickets, rabbits
Secondary consumers eat primary consumers
Examples: fox, snake
Tertiary consumers are at the top of the food web
Example: shark, lion, human
Decomposers break down dead matter for energy, allowing plants to use those nutrients again
Example: mushrooms, bacteria, worms

3. PREY  PREDATOR

4. How Are All of These Organisms Connected in an Ecosystem?
Populations are interdependent
If the population of one organism changes, it will affect all the populations connected to it.
Food chains/webs show interdependence. You can use it to predict how a change in one population will affect other organisms.

5. 3 General Rules (Common Sense!):
1. When prey change  Direct Relationship:
prey ______ = predators ______
2. When predators change  Inverse Relationship:
predators ______ = prey ______
3. Decreasing the population of producers decreases all the other organisms in the food web.

6. Check for Understanding
What is the producer in this ecosystem? Algae
What would happen to the rest of the food chain if the algae population were to increase?
All other trophic levels would increase.
3. What would happen to the hawk population if the algae were to decrease?
All other trophic levels would decrease.
4. What would happen to each trophic level in this food chain if the perch population increased?
Hawk: increase, Minnow: decrease, Zooplankton: increase, Algae: decrease

8. Mesquite bush: increase; Horned Lizard, Snake, & Hawk: Decrease

9. Humans used pesticides to dramatically lower the population of grasshoppers in this ecosystem. Predict the effects to the rest of the organisms.