Let's explore the various tools biologists use to study and monitor the movement of matter and energy in an ecosystem. Food chains, food webs, and ecological pyramids help us understand who eats whom and how changes in a population of organisms can impact predators and prey. Before you get started, don’t forget to print out the OnTRACK Biology Journal. 

TEKS Standards and Student Expectations

B(12) The student knows that interdependence and interactions occur within an environmental system. The student is expected to:

B(12)(C) analyze the flow of matter and energy through trophic levels using various models, including food chains, food webs, and ecological pyramids

Learning Objective

Describe and apply the tools scientists use to study the movement of matter and energy within environmental systems, including food chains, food webs, and ecological pyramids.

Essential Questions

How do matter and energy move through an ecosystem?

What happens when an energy resource in an ecosystem becomes depleted?

Vocabulary

Check your prior knowledge. Before completing this resource, check the boxes of the vocabulary words that you already understand in your OnTRACK Biology Journal.

• Organism
• Ecosystem
• Autotroph
• Producer
• Photosynthesis
• Heterotroph
• Consumer
• Secondary Consumer
• Tertiary Consumer
• Quaternary Consumer
• Carnivore
• Herbivore
• Omnivore
• Decomposer
• Food Chain
• Food Web
• Trophic Level
• Kilocalorie
• Ecological Pyramid
• Pyramid of Energy
• Pyramid of Numbers
• Pyramid of Biomass
• Biodiversity
• Invasive Species

Now view the video to review the components of a food chain and see a real life example in the Everglades ecosystem, which is a region of tropical wetlands found in the southern portion of Florida. Use the graphic organizer on page 4 in your OnTRACK Biology Journal to take notes from the video.

Compare your notes to those of a classmate. Make sure you both have a complete set of notes that includes all the terms from the video. If you don’t, view the video again.
 

Ecosystem Research
An ecosystem is a community of living organisms in conjunction with the nonliving components of their environment (things like air, water, and soil), interacting as a system.

In the video, the Everglades ecosystem was used to show how energy and matter flow from one organism to another. What other kinds of ecosystems do you know about? In Texas, we have many ecosystems, such as deserts, mountains, plains, prairies, seacoasts, timberlands, and marshes. Choose one type of ecosystem you are curious about and brainstorm at least three questions to research. Write them on page 5 in your OnTRACK Biology Journal. Include some of the new terms you have learned in your questions by referring to page 4 of your OnTRACK Biology Journal. Use available resources to research and answer your questions and write them in your journal. You will use this information later.

In every ecosystem, organisms are linked through feeding relationships. There are a great many feeding relationships in any ecosystem, but energy always flows from primary producers to various consumers. These feeding relationships are represented by food chains and food webs. 

A food chain is a sequence in which organisms transfer energy by eating and being eaten. Here is an example of a food chain from the video.

Notice that the arrows point in the direction of the energy flow. The point of the arrow goes to who is doing the eating.

In most ecosystems, feeding relationships are much more complicated than the relationships shown in a food chain. The network of feeding interactions is called a food web. View the video to see an example of a food web from the Everglades ecosystem.

Compare and contrast a food chain and a food web on the graphic organizer on page 6 of your OnTRACK Biology Journal. Use the Venn diagram to list the features of a food chain and food web as well as what the two have in common.
 

Check Your Learning
Drag the circle icon and place it over the arrow that is pointing in the correct direction in the following diagram.

Make Your Own Food Web
Now that you have seen an example of a food web, refer to the ecosystem you researched in the first section of this resource and create a food web to show how matter and energy flow between organisms that are likely to live in that ecosystem. You can show your food web on a poster or through a digital graphic organizer created online such as in Lucidchart or in Google Drive with Google Drawings. Remember to draw the arrows moving in the direction that the matter and energy are flowing.

Once your food web is complete, label each of the following:

• Producers
• Consumers
• Herbivores
• Omnivore
• Carnivore
• Decomposers
• Scavengers

Additionally, complete the following and post near or on your food web diagram:

Describe the food web and the places on Earth where this ecosystem and these organisms might be found.

Have you ever heard the phrase, “top of the food chain”? What does this phrase mean? What kinds of organisms are typically at the top of the food chain?

Look at the food web you created at the end of the previous section, Energy Flow in Ecosystems. Count how many organisms are between the top of the food chain and the sun. Keep this activity in mind as you complete the next section. Be sure to take notes on any new concepts on page 7 of your OnTRACK Biology Journal.

Each step in a food chain or food web is called a trophic level. Trophic is derived from the Greek word for nutrition. In ecology, it means of or relating to feeding and nutrition. Therefore, a trophic level is a feeding level. Primary producers always make up the first trophic level as they are the basis of all other nutrition. Various consumers occupy every other level.

The shape of a pyramid is used to show the difference in the amount of energy at each trophic level in a food web. We call these diagrams ecological pyramids. Most of the energy is found at the bottom of the food web where the producers are found, and more and more energy is lost as it travels from organism to organism. On the following pyramid, place the term in the correct trophic level on this ecological pyramid by dragging and dropping them into the blanks next to the organism’s photo.

As we explained before, most of the energy in a food web is found at the bottom of the ecological pyramid where producers are found. These producers obtain their energy from the sun. As these plants are consumed by primary and secondary consumers, most of the energy is used by the animal, and very little is passed to the next consumer.

Refer back to the food web you created at the end of the previous section. Can you identify producers, first level or primary consumers, secondary consumers, third level or tertiary consumers, and fourth level or quaternary consumers in your food web? Use these organisms to create an ecological pyramid on page 7 of your OnTRACK Biology Journal. Find a friend to share your pyramid with!

Consider the difference between the temperature in the room and the temperature inside your body. Why do you think your body is able to stay so much warmer than the air around it? Did your response have anything to do with the fact that much of the energy we get from food is used to keep us warm?

We're going to learn how energy moves up the food chain, the different ways it can be measured, and how most of that energy is lost as heat at each level.

You've already learned about ecological pyramids. There are three main types of ecological pyramids: pyramid of energy, pyramid of numbers, and pyramid of biomass.
 

Pyramid of Energy
A pyramid of energy shows the relative amount of energy available at each trophic level of a food chain or web. On average, about 10 percent of the energy available within one trophic level is transferred to the next level. The other 90 percent is given off as heat during metabolic processes that allow our bodies to function. In this pyramid, the energy is expressed in Kcal or kilocalories. In this pyramid of energy, you will see the primary producer and consumers from the videos. What do you notice when you look at the number of kilocalories at each level?

Pyramid of Energy Interactive - Image Sources:

Periphyton

Mosquito Larvae

Gambusia Affinis

Myakka River Blue Heron

American Alligator

Pyramid of Biomass
A pyramid of biomass shows the relative amount of organic matter, or living tissue, available at each trophic level in an ecosystem. Biomass is usually measured in grams or kilograms of organic matter per unit area.

Not all ecological pyramids are uniform in structure. For example, look at the pyramid below. Notice the bottom level is smallest. This represents a pyramid of biomass from the ocean ecosystem. Phytoplankton is the producer. They are so small and weigh so little that there is very little biomass.

Pyramid of Numbers
A pyramid of numbers shows the relative number of individual organisms at each trophic level in an ecosystem.

Again, not all pyramids of numbers have the largest amount at the bottom. Look at this pyramid of numbers in a forest. One oak tree provides nutrition for 2000 insects, which feed 90 sparrows and one hawk.

Why Does It Matter?

Biodiversity is essential to all organisms living in an ecosystem. Picture these organisms on a balance scale. If one of the organisms is removed or its population decreases or increases drastically, the scale is thrown off the balance. For a real life example of how this can happen, listen to the following podcast about the Florida Everglades ecosystem and respond to the comprehension questions on page 10 of your OnTRACK Biology Journal.

Ecologists and biologists keep a watchful eye on human activity in threatened ecosystems like the Everglades. Choose a type of ecological pyramid. Respond to the following prompt on page 11 of your OnTRACK Biology Journal:

• How could this pyramid help biologists study and track the balance of matter and energy in an ecosystem? Provide an example.
   

Invasive Species
Invasive species are plants, animals, or pathogens that are non-native (or alien) to the ecosystem under consideration and whose introduction causes or is likely to cause harm.

View the linked video about several invasive species found in the Everglades.

//www.nps.gov/media/video/view.htm?id=F7B580CC-1DD8-B71C-07EE48C133240AE7
 

Complete the ecological pyramid for before and after the Burmese Python was introduced to the wetlands on page 9 of your OnTRACK Biology Journal. Respond to the following prompts in your journal:

• In what ways did the introduction of the Burmese Python impact the organisms native to the ecosystem?
• What are some reasons the Burmese Python thrives in the Everglades ecosystem?
• What are some reasons humans are responsible for responding to these problems?

Extend Your Knowledge
To learn more, visit the National Invasive Species Information Center. Identify an invasive species in Texas that has a negative impact on the flow of matter and energy in an ecosystem. Create a presentation to share your understanding. Your presentation should demonstrate how this species fits into the ecosystem’s food web, the consequences of the introduction of this species to the ecosystem, and current efforts to respond to the problem as well as any actions citizens can take to help.