Do now: Characterize the feeding relationships in this food web.

Question: How does energy enter this food web?

Energy enters a food web Green plants and algae (autotrophs) use sunlight to synthesize nutrients. What is the process called? Some of the energy in the sunlight is now stored in the bonds of the glucose molecules.

What do you notice about this figure? Does this diagram look like a certain shape? Why do you think it is titled “How many”?

Aim How can we explain the pyramid of energy?

How does energy flow in a food chain? Energy flows from the producers to the primary consumers to the secondary consumers.

Energy pyramid The amount of energy available in the different levels of an ecosystem is commonly depicted as a pyramid. Question: How does the amount of energy at the producer level compare with the energy at the top consumer level?

Energy levels The greatest amount of energy is present in the producers and the least amount of energy is present in the highest consumers. Question: Why do you think this is so?

Each energy level contains less than the previous level Each level contains only about 10% of the energy in the previous level. Question: Why does the total energy available decrease with each higher feeding level? Demonstration

How is the energy going away? Some energy is used by the plant for its own survival for processes involved in metabolism Some is released or dissipated as heat. This cannot be used by organisms as an energy source. Some is used to make new tissue in growth As we just saw, herbivores might only eat some parts of the plants (such as the fruit but not the wood) Thus, a lot of energy is not directly used by the consumer.

Question Why does energy have to be continually put into an ecosystem? Because energy is always lost in an ecosystem. Plants need to constantly grow to replenish the lowest source of energy in a food web. What is the ultimate source of energy in any ecosystem?

Group activity Now that we know about energy levels in a food web, let’s think about the total mass of living organisms at each energy level. This is called biomass. Predict how the total mass of living organisms at each level would compare. Justify your prediction.

As energy levels decrease, biomass also decreases

In successful, self-sustaining ecosystems, there must be a great deal more biomass in previous energy levels

What do you think happens deep under the ocean, where there is little sunlight?

Ecosystems that do not depend on the sun for energy Instead of using photosynthesis, these producers use chemosynthesis for energy The producers use energy obtained from the oxidation of hydrogen sulfide rather than from the sun

Summary Summarize, in words or in a diagram, the relationship between energy levels and biomass levels in a food web

Bottle ecosystems Take 5 minutes to make observations about your ecosystem. Remember that the fish is dead is a CONCLUSION. What do you see that makes you conclude that the fish is dead? Do you see changes in abiotic factors? Water changing colors?

Homework Due Wednesday. Design and create your own food web. Search on the web for an ecosystem and either draw or make a collage of an ecosystem that you are interested in. Due Thursday: The materials and methods section from your bottle ecosystem lab report. Friday: Microscope lab. Lab report is due on Monday.