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

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

PREY  PREDATOR

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.

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.

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

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

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