Most biological energy here on Earth can be traced back to one single source: the sun. Plants and blue-green algae use photosynthesis to trap the electromagnetic wave energy generated by the sun, transforming it into chemical energy in the form of food for themselves and for other creatures that eat them.

Sounds simple so far, right? In an effort to simplify the way you think about creatures and their energy relationships, you often use food chains that show a very clear link between creatures and the things that eat them. Here is one example:

Rose bush > Beetle > Robin > Domestic Cat > Coyote

Organisms are connected by an arrow that points toward the creature consuming it.

While this kind of chain is great for visualizing how some creatures eat, it is not very realistic since most creatures eat a variety of foods. Most robins, for example, like to eat many kinds of insects, not just beetles.

You can learn more about the ecological relationships and the flow of energy through food chains and food webs by clicking on the publisher resources for chapter 3 and selecting "Biology Basics." On this page, find and explore the study module "Ecosystems and Communities."

To demonstrate how real creatures behave and to better portray the flow of energy through an ecological community, food webs are often used as described within the energy flow section of the module above.

Please respond to the following questions throughout the week. Focus on part 1 early in the week and part 2 after you have completed the unit Readings and explored the provided materials within this prompt. You will have two main posts this week in addition to the minimum of two responses to your classmates.

Energy and Food Webs

Part 1:

• Provide an example of a food chain in the area where you live.
• Humans are parts of food chains and food webs, too. Where on a food web would you typically find humans (near the bottom with the producers, at the top with carnivores, or somewhere in between)? Explain.
• What are some advantages of being part of a food web rather than a food chain?

Part 2:

Here is a food web for Lake Michigan:

http://www.glerl.noaa.gov/pubs/brochures/foodweb/LMfoodweb.pdf 

To see this PDF, you will need to download the free Adobe Reader.

• In the Lake Michigan food web, is it possible to identify the most important producer? Why or why not?
• What would happen if there was a change in the population size for any one of the producers (either an increase or a decrease)? How could these changes impact other producers and organisms on other trophic levels?
• Provide at least two types of impacts that humans could have on this food web.
• Read the description of the sea lamprey on page 2 of the food web. This species is described as non-native.
  • Propose a mechanism for how this fish was introduced to Lake Michigan.
  • What challenges could occur within a food web when a new predator like this is introduced into an ecosystem?
  • What natural population controls are missing for this species within this food web?
  • Do you think steps should be taken to eradicate this species from the food web? Explain why or why not? If so, what steps can be implemented?