1. Food Chains, Food Webs, and the Transfer of Energy

2. Standards
S7L4 Students will examine the dependence of organisms on one another and their environments.
Demonstrate in a food web that matter is transferred from one organism to another and can recycle between organisms and their environment.

3. Standards Continued
Explain in a food web that sunlight is the source of energy and that this energy moves from organism to organism.

4. Essential Question:
How is energy transferred from one organism to another?

5. What is the source of all energy?
The sun is the source of the energy that cycles from organism to organism. The sun helps drive the cycle of energy being converted from potential energy to kinetic energy.

6. What are autotrophs or producers?
Autotrophs, also called Producers, produce all of the food that heterotrophs use.
Producers use the process of photosynthesis to make their own food.
Without autotrophs, there would be no life on this planet
Ex. Plants and Algae

7. Autotrophs

8. What are heterotrophs or consumers?
Organisms that can not make their own food but depend on other consumers or producers for food are called heterotrophs or consumers
Another term for Heterotroph is consumer because they consume other organisms in order to live
Ex. Rabbits, Deer, Mushrooms

9. Heterotrophs

10. What are the types of consumers?
Detritivores
Herbivores
Carnivores
Omnivores
Decomposers

11. What is a detritivore or scavenger?
Scavengers or detritivores feed on the tissue of dead organisms (both plans and animals)
Ex. – Vultures and Crows

12. What are herbivores? Herbivores are consumers that ONLY eat plants
Ex. – Cows, Elephants, Giraffes

13. What are carnivores? Carnivores are consumers that ONLY eat meat
Ex. – Lions, Tigers, Sharks

14. What are omnivores?
Omnivores are consumers that eats BOTH plants and animals
Ex. – Bears and Humans

15. What are decomposers?
Decomposers absorb any dead material and break it down into simple nutrients or fertilizers
Ex. – Bacteria and Mushrooms

16. Transfer of Energy
When a zebra eats the grass, it does not obtain all of the energy the grass has (much of it is not eaten)
When a lion eats a zebra, it does not get all of the energy from the zebra (much of it is lost as heat)

17. Transfer of Energy
The two (2) previous examples of energy transfer show that no organism EVER receives all of the energy from the organism they just ate
Only 10% of the energy from one trophic level is transferred to the next – this is called the 10% law

18. What are trophic Levels?
Energy moves from one organisms to another when it is eaten
Each step in this transfer of energy is know as a trophic level
The main trophic levels are producers, consumers, and decomposers

19. What is a food chain?
A food chain is a linear pathway depicting the flow energy from one organism to another.
A food chain is linear, simple and direct.
It involves one organism at each trophic level
Primary Consumers – eat autotrophs (producers)
Secondary Consumers – eat the primary consumers
Tertiary Consumers – eat the secondary consumers
Decomposers – bacteria and fungi that break down dead organisms and recycle the material back into the environment

20. Food Chain

21. Food Web
A complex network of feeding relationships among several different organisms.
Resembles a spider’s web and is complex, involving many organisms.
When many organism are involved it is know as a FOOD WEB

22. Food Web

23. What does the arrow in a food web or food chain mean?
The arrow  points in the direction of the energy transfer.
Ex. The elk provides energy to the gray wolf
Elk Gray Wolf

24. Food Web

25. Biomass
The total mass of the organic matter at each trophic level is called biomass
Biomass is just another term for potential energy – energy that is to be eaten and used.
The transfer of energy from one level to another is very inefficient (10% Law)

26. Biomass

27. What is an ecological pyramid?
Ecological pyramid show the relationship between consumers and producers at different trophic levels in an ecosystem
Shows the relative amounts of energy or matter contained at each trophic level
The Pyramid shows which level has the most energy and the highest number of organisms

28. Ecological Pyramid

29. Ecological Pyramid

30. Ecological Pyramid Which level has the most energy?
Which level has the most organisms?
Which level has the least organisms?
Which level has the least energy?