1. Food Chain Analysis Define: Trophic Level Energy Transfer
Why is less energy available at each trophic level?

3. Laws of Thermodynamics
1st Law
Explains energy use
2nd Law
Explains energy transfer

4. Ecological Pyramids
Food chains and webs are good visual models, but do not represent the amount of energy available or number of organisms at each energy level
Ecological pyramids provide ecologists with more accurate measures of the energy available to each trophic level
They are graphed using a scale
There are three types of pyramids:
Pyramid of Numbers
Pyramid of Biomass
Pyramid of Energy

5. Pyramid of Numbers
Depicted by counting the number of organisms in the population or community in each trophic level
Usually forms a regular pyramid
BUT…
sometimes you can have inverted pyramids – WHY??
Benefits: High Accuracy
Drawbacks: Time consuming, does not take size of organisms into account

6. Pyramid of Numbers

7. Pyramid of Biomass
Depicted by measuring the amount of biomass in the organisms within a population or the community
Biomass is the dry mass of living (or once living) organisms within a certain area (g/m2)
Can have inverted pyramids
Benefits: Excellent indicator of food energy stored/present at each trophic level
Drawbacks: Scientists define biomass in different ways (including dead material), and it’s time consuming

8. Pyramid of Energy
Depicts the total amount of energy transferred through each trophic level within a population or community
Cannot be inverted – WHY NOT?
Benefits: Shows a visual understanding of energy distribution (available energy at each level)
Drawbacks: Not as accurate

9. Drawing Ecological Pyramids
Using information provided about an ecosystem you can create a pyramid by using a scale