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

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

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

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

Pyramid of Numbers

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

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

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