Food chains show the dietary relationships between all living things. A food web may contain several interconnected chains. Studying food chains and webs at the high school level will enable you to see this interconnectedness and to understand the complex relationships of energy and matter flow within an ecosystem. To open and download the worksheets, click on the image you require and a PDF should open up. If you need help, follow this guide for working with Adobe printables.
Worksheet one can be considered a learning activity which will help consolidate your ideas in graphic form. The first part of worksheet one contains a food web which can be found in a woodland ecosystem. There are several food chains within this web. Some examples of these are:
- Oak Tree - Squirrel - Fox
- Oak Tree - Earthworm - Mouse - Owl
- Oak Tree - Caterpillar - Shrew - Owl
Activity: Part One
Using the words from the helpful terminology section below to assist you, have your student complete this worksheet by deciding whether each organism in the diagram is a producer, a decomposer, a primary consumer, a secondary consumer, or a tertiary consumer. Then have your student label each organism as a herbivore, omnivore, or carnivore, paying attention to where particular dietary groups fit into the food web.
Activity: Part Two
Have your student label the five levels of the trophic pyramid, using the organisms from the word bank on the worksheet. Even though there will be many correct versions of the pyramid, the student should be able to demonstrate that the producers they have chosen for the bottom level of the pyramid can be consumed by the primary consumers, the primary consumers by the secondary consumers and so on, all the way to the quaternary trophic level.
Trophic levels can be described as the feeding positions of particular organisms within a food chain. CK-12's trophic level table provides extensive information on trophic levels.
The Movement of Energy
Trophic levels in a food chain can also be discussed in terms of energy. The pyramid depicts how both energy and substances are passed from one trophic level to the next, and how much of the energy is lost to the environment. Approximately ten percent of energy is passed on from one level to the next. That is why a trophic pyramid is usually pyramid shaped.
An Example of a Trophic Pyramid
The first level of the pyramid might be clover plants. This level will always be a producer. It takes many clover plants to support, for example, a snail population which feeds upon it. Therefore, the next level would show that there were fewer snails than clover. In turn, birds might feed upon the snails and there would be fewer birds than snails. The final level in this pyramid might be birds of prey, such as hawks. There would be an even smaller number of hawks which could survive upon the population of other birds. However, it is important to note that if the producer in the food chain is a single tree, the trophic pyramid would look less like a pyramid and more like a diamond because one tree might support a large number of primary consumers. For more information and images of trophic pyramids see Britannica.com.
Biomass is also depicted as a pyramid. It describes the mass of the organism or organisms available at each level of the chain rather than the population. This BBC high school guide provides an in-depth review of biomass.
Worksheet two allows you to use information from this lesson plan to test your student's knowledge. Worksheet two can be administered as a quiz and will test your student's knowledge of the terminology and facts found in the material below.
Activity: Part One
Have your student match the definitions on the left labeled A through N to the vocabulary terms on the right. They may choose their answer for each and fill in the correct letter in the column on the right.
Activity: Part Two
Administer the five multiple choice questions as a mini quiz.
You may remember many of these words and terms from your study of food chains at the elementary or middle school level. If you missed out, this helpful article will provide an introduction. In case you need a vocabulary refresher, here are some useful terms:
- Herbivore - An organism which feeds on the nutrients from plants.
- Carnivore - An organism which feeds on the nutrients found in animals.
- Omnivore -An organism which feeds on both animal and plant nutrients
- Food chain - A sequence (or diagram) of the eating relationships between organisms and the movement of energy through trophic levels
- Biomass - The mass of an organism
- Primary consumer - The name given to an organism (a herbivore or omnivore) that eats a producer
- Dry mass - The mass of an organism after its water content has been removed
- Decomposer - An organism which eats dead material or animal droppings and breaks them down into simpler materials
- Producer - An organism, such as a plant, which absorbs the sun's energy and converts it into food
- Secondary consumer - An organism (omnivore or carnivore) that obtains its energy by eating the primary consumer
- Trophic level -The position of an organism in a food chain, food web, or pyramid
- Ecosystem - A community of animals, plants, and microorganisms in a particular habitat
- Food web - A network of food chains, showing how they link together
- Photosynthesis -A chemical process used by plants and algae to make glucose and oxygen from carbon dioxide and water, using light energy and producing oxygen as a by-product
- Habitat - A place where plants, animals, and microorganisms live
- Tertiary consumer - An organism (usually a carnivore) that obtains its energy by eating the secondary consumer
- Quaternary consumer - An organism (carnivore) that obtains its energy by eating the tertiary consumer
The Circle of Life
It is important to remember that all organisms within a particular environment are interconnected and are dependent upon each other for their food and survival. Food chains begin with producers who use photosynthesis to obtain nutrients from the sun and end with the highest level of consumers found in that particular environment. When those consumers die, the decomposers ingest their nutrients and provide sustenance to consumers in their turn. Food webs and food chains are part of the circle of life.