1. Food Webs
S&S 2.2

2. Do Now
Respond to the following question in your lab notebook:

3. Lesson Target
I can create a food web that shows the transfer of chemical energy within an ecosystem, and I understand that not all energy makes it to the next level.

4. Vocabulary
Food chain- a linear representation of how food is transferred from one organism to another.
Food web- A web that shows all of the feeding relationships within an ecosystem.
Trophic Level- feeding levels within an ecosystem- the producers are in the first trophic level.

5. Vocabulary
Law of Conservation of Energy- Energy cannot be lost because it cannot created or destroyed.
Calories- a measure of the amount of energy stored in food.

6. Every organism, dead or alive is a potential source of food for other organisms

7. Food Chain
Used to show how energy is transferred, via food, from producers to primary consumers, from primary to secondary consumers, and so on

9. Food Chains cont.
In nature, many consumers feed on both producers and other consumers, because of this, a Food Chain may not adequately describe all the pathways of energy transfer.

10. Food Webs
A diagram that illustrates the transfer of chemical energy within an ecosystem

13. Trophic Levels
Based upon its position in the Food Web, each member of an ecosystem can be assigned to a Trophic Level

14. First Trophic Level
Producers [plants and plankton]

15. Second Trophic Level
Primary Consumers [usually herbivores]

16. Third and Fourth Trophic Levels
Secondary and tertiary consumers [carnivores and omnivores]

17. Whenever one organism eats another, chemical energy is transferred to a higher trophic level Some energy is not used by the consumer; some is transformed into heat, some remains in the food not eaten The amount of energy stored in food is measured in CALORIES

19. Procedure 1; page 21
Draw a Food Web, showing energy transfer among: Trout Gulls Humans Catfish Minnows Bacteria Insects Phytoplankton Herbivorous zooplankton Carnivorous zooplankton

20. H/W Questions p22; 1 - 4
1. Rank the organisms in your Food Web from most abundant in the ecosystem to least abundant in the ecosystem. Explain how you determined your rankings.

21. H/W Questions p22; 1 - 4
2. When 1 organism eats another, not all of the energy stored in the food gets transferred to the consumer. What happens to the energy that is “lost” during each transfer?

22. H/W Questions p22; 1 - 4
3. In 1 m3 of a typical open ocean ecosystem, phytoplankton can generate 1,600,000 Calories of chemical energy per year. Assume there is an 80% “loss” of usable energy during transfers from one trophic level to another. Make a Data Table AND Graph showing energy available at each of the first 5 Trophic Levels.

23. Available Energy [Calories]
TITLE?
Trophic Level
Available Energy [Calories]
1st
1,600,000
2nd
3rd
4th
5th

24. Responding Variable
TITLE?
Manipulated Variable

25. H/W Questions p22; 1 - 4
4. How many more humans could be fed if everyone ate from the second trophic level rather than the fifth. Is this a reasonable possibility? EXPLAIN.