1. 7 th Grade Science FOOD WEBS AND CHAINS

2. OBJECTIVES Define and give examples of organisms at different trophic levels Describe how energy flows in a food chain. Explain why producers must outnumber consumers in a balanced ecosystem.

3. PRODUCERS Food chains begin with producers organism that makes its own food Green Plants use energy from the Sun to create food through photosynthesis Make up Trophic Level in an ecosystem Examples: Grass, Trees, and Algae

4. CONSUMERS Organism that get their energy by eating other organisms “YOU” cannot make your own food, no matter how hard you try! Must obtain energy from other sources to live and grow (EAT!!!!!) All animals, including humans are consumers

5. PRIMARY CONSUMER First consumer in Food Chain Obtain energy directly from “Producers” a.k.a—”HERBIVORES” or plant eaters Land Ecosystem Herbivores include: Cows, Deer, and Grasshoppers Aquatic Ecosystem Herbivores include: Shrimp, Minnows, and Snails

6. LAND ECOSYSTEM HERBIVORES

7. AQUATIC HERBIVORES

8. SECONDARY CONSUMERS Eat Primary Consumers Include “Carnivores” (meat eaters) Lions, Tigers, Coyotes, and Wolves

9. TERTIARY CONSUMER Eats “Secondary Consumer” Includes: Carnivores and Omnivores Carnivores: Only eat meat Omnivores Eats both meat and plants Examples of Omnivores: Humans and Bears

10. DECOMPOSERS Last link in a food chain Break down nutrients in dead organisms and return essential chemicals to earth: Nitrogen (N), Carbon (C), and Phosphorous (P) In land ecosystems, chemicals are released into soil. In aquatic ecosystems, chemicals are dissolved in water. Essential part of an ecosystem because: Producers absorb nutrients to make food Most common Decomposers are: Bacteria and Fungi

11. ENERGY FLOW Where do you get energy to read, come to school, hunt, and play ball? Eating what? Food!! All energy as you already know, comes from the Sun Producers absorbs the energy and uses “Photosynthesis” to make food 50% of energy absorbed from Sun is used to live and grow Unfortunately not all energy is transferred to consumer, due to heat “loss” Only around 10% of energy is transferred from producer to consumer

13. BALANCED ECOSYSTEM Producers outnumber consumers greatly More Specifically: Producers outnumber Primary Consumers Primary Consumers outnumber Secondary Consumers Secondary Consumers outnumber Tertiary Consumers and so on……. Since energy decreases 10% with each Trophic level, it is very important for higher level consumers to eat a lot to get enough energy to survive. Example: Even though a mouse only has to eat a few stalks of grass to have energy, a snake must eat several mice to survive. To take this one step further, a hawk has to eat even more snakes!

14. TROPHIC PYRAMID

15. FOOD WEBS Used to represent the complex food relationships between organisms in an ecosystem. Network of interconnecting food chains

16. FOOD WEB #2

17. END OF CLASS REVIEW How much energy is transferred from one trophic level to the next? Describe a Balanced Ecosystem. Where do producers get their food and how? What are the 3 types of consumers? How do they get their food? Describe a food web