Lesson Plan - Get It!
What is a food web? Is it where a spider has lunch? What are examples of producers, consumers, and decomposers that live in the ocean?
All ecosystems have a food web.
What is a food web? Tell your teacher or parent what you think it is.
A food web is an interlocking system of food chains that displays how energy is transferred between organisms in an ecosystem.
Food webs are made up of producers, consumers, and decomposers.
- Producers are organisms that produce their own food.
- Consumers are organisms that feed off other organisms. Some consumers eat plants (herbivores), some eat meat (carnivores), and some eat both plants and meat (omnivores). When looking at a food web, consumers are often divided into two groups; primary consumers and secondary consumers. Primary consumers are herbivores, and secondary consumers are carnivores and omnivores.
- Decomposers are organisms that eat dead and decaying matter.
The image below shows an example of an ocean food web. Notice how the lines show what living organisms consume other living organisms. Tell your teacher or parent which organisms are producers and consumers:
You have noticed decomposers are not a part of this food web. Decomposers are not always shown on a visual representation of food webs. Tell your teacher or parent what some examples are of marine decomposers, and what role they might play in the food web shown above. (If you are uncertain, check out the Elephango lesson in the right-hand sidebar under Additional Resources to find some examples of the ocean's decomposers.)
The transfer of energy always moves in a cycle from producers, to primary consumers, to secondary consumers, and finally to decomposers. This is a never-ending cycle.
The transfer of energy always begins with the sun, because sunlight is needed for plants to make their own food during the process of photosynthesis. All food webs start with producers. What organism is the start of all ocean food webs? Tell your teacher or parent.
If you said phytoplankton, you are correct! Phytoplankton are the most basic form of plant life in the ocean, and are responsible for about 50% of the oxygen in Earth's atmosphere.
Primary consumers such as zooplankton and small fish consume phytoplankton. The primary consumers are eaten by larger fish and sea creatures, such as squid. Finally, these secondary consumers are consumed by even larger secondary consumers, such as sharks, whales, and dolphins. All dead and decaying animals are consumed by bacterioplankton, who are decomposers, and recycled back into the ocean as nutrients.
Watch Exploring Ecosystems: Coastal Food Webs | California Academy of Sciences (California Academy of Sciences, below) to see an example of a marine food web. As you watch the video, make a list of the producers, primary consumers, secondary consumers, and decomposers that are shown in the video:
When you are finished watching the video, have your teacher or parent check over your list. Discuss what would happen to this particular food web if one of the organisms shown became extinct.
When you are finished discussing what you saw, move on to the next section to practice creating your own ocean food web!