Biology Lessons Part 2: Population Biology

Lesson 2.3: Chaparral Community

To Ponder
Introduction and Background

AAAS Benchmarks
Exercise 1: Examine the Chaparral Graphic
Exercise 2: Identifying Animals in the Semnet
Exercise 3: Organizing Knowledge about Plants
Exercise 4: Roles of Organisms in the Community
Exercise 5: Classify Organisms According to their Various Roles in the Community
Exercise 6: Trophic Levels in the Community
Exercise 7: Interactions in the Chaparral Community

Grade Level

Prospective and Practicing K-8 Teachers; may be adapted for use in K-12 classes.



Approximately 2.5 hours.

To Ponder

1. What does it mean to eat "lower on the food chain" in a food web?
2. Why would anyone recommend eating lower on the food chain?

What are predators? Are humans predators?



These are some materials you may want for the sample experiments supplied with this lesson.

  •  picture of some of the inhabitants of a chaparral community (Figure 1)
  • semantic network of the food web in this community (2.3b ChaparralComm LessonNet)
  • SemNet software

*To get the SemNet software and the 2.3b ChaparralComm Lesson Net click here.



Develop an understanding of biological communities by examining a chaparral community composed of many different types of organisms.


Become familiar with the interactions in a food web.


Distinguish between a food web and a food chain.


Identify the trophic levels in a food chain.


Distinguish between an organism's role and niche.



In this lesson, we will consider some of the organisms that live in a chaparral community and the interactions among them. Chaparral consists of thick shrubs and low trees. It is characteristic of the environment of San Diego State University's (SDSU's) Biological Field Stations. In addition to chaparral, the field stations also include coastal sage scrub, oak woodland habitats, and riparian (river) systems.




A biological community consists of groups of organisms of two or more different types living together within the same geographical area where they are likely to interact with each other.


  3.  Do you know if all domestic dogs are members of a single species? Explain.



Give three examples of different human populations.




Exercise 1 Examine the Chaparral Community Graphic
     1. Figure 1 on the next page shows the community of organisms we will study. Each organism is identified by a number shown above it; the numbers below each organism indicate the creatures that this organism eats. We'll use SemNet to "unpack" this complex graphic and to examine the food web within this community.

Figure 1 (click on "Chaparral Community Graphic" below) has been adapted from the Audubon Nature Encyclopedia, Volume 4, pages 708-709 (New York: National Audubon Society, Curtis Publishing, 1965).

Interactive Chaparral Community Graphic


Each individual organism in Figure 1 represents an entire population of such organisms that are living in the chaparral community.

 Exercise 2    Identify the Animals in the Chaparral Community SemNet
  To Do    1.

Identify the different types of animals represented in the chaparral community SemNet. To do this, open the "2.3b ChaparralComm LessonNet" by double clicking on it. Go to the Display menu and look at Concepts ­ Alphabetically. Scroll past the numerical synonyms for organisms (which correspond to the numbers in the graphic) down to the point where the first animal, bobcat, appears in the left column. List all the types of animals that have been described in this web in Table 1 below. Remember that each type of animal represents an entire population, a multigenerational group of interbreeding organisms of that type.

Table 1. Some Animal Populations in the SDSU Biological Field Stations


  Exercise 3  Organize your Knowledge about Plants in the Chaparral Community
To Do   1. 

How many types of plants are in the net and what are they? To figure this out, let's build a hierarchy. Create the instance, "chaparral community include(s) plant". Then double-click on the concept, plant, and create the instance, "plant has type herb. Do this with each type of plant in the net.



Let's add two additional plants, tree and shrub. Connect them to the concept, plant, using the relation type of (tree [is a] type of plant). The reverse relation ray is has type. We are adding these because, while they are shown in the Audubon graphic, their parts (rather than the entire plants) are referred to by numbers. In contrast to ferns grass, and herb, which are herbaceous plants, tree and shrub are woody plants.


Identify the plant parts in the net by looking at Concepts ­ Alphabetically on the Display menu. List the plant parts in Table 2 below.

Table 2. Plant Parts in the Chaparral Community



Using the relation has part, connect the parts of each plant to the appropriate plant types. The reverse relation ray is has part.





Exercise 4

Roles of Organisms in the Community

Background 1. Many different food chains are embedded in a food web. The term food chain describes the transfer of matter and energy from green plants through a series of animals. Matter and energy are transferred when animals eat plants or eat other animals. A food chain describes a particular linear set of relationships (A eats B eats C, etc.). It is sometimes useful to think of each successive meal in a food chain as the next "higher" level (further away from the source which is the producer). Food chains are snapshots in both space and time. The composition of a chain at any given point is determined by what specific organisms individual animals have recently eaten.

Since animals usually consume more than one other type of organism, and different types of organisms compete for the same food sources, each animal is likely to be a part of multiple food chains. A food web illustrates these complex interconnections in the feeding relationships in a community. You can see some of this complexity in Figure 2, which illustrates part of the food web in the chaparral community.

Figure 2. A portion of the chaparral community food web.

To Do 3.

Draw two different food chains embedded in this food web.


Background 4. All the types of organism in the chaparral community are members of a single food web. The green plants, called producers, are at the bottom of the food web. Plants use light energy from the sun and carbon dioxide from the air to produce organic molecules called sugars, via a process called photosynthesis. Photosynthesizers are called producers because they are the only organisms capable of converting inorganic molecules (carbon dioxide and water) into organic molecules (sugar). All other organisms obtain their organic molecules, directly or indirectly, from the producers.
To Do 5.

In the space below, list the producers in this chaparral community.




Questions   6.  Can you define a consumer? A primary consumer?
    7.  Define predator and prey.
    8.  What is a top predator? Are there any top predators in this community? If so, what are they?
    9. Decomposers are an essential part of the natural cycle. What do decomposers do?

Which six types of organisms in the chaparral community net function as decomposers?



Exercise 5

Classify Organisms in the Chaparral Community SemNet According to their Various Roles in the Community

To Do 1.

Using the concepts predator, prey, producer, decomposer and primary consumer, identify the role(s) played by each of the 5 types of plants, the 31 types of animals, and the fungi in this chaparral community. Choose Concepts - Alphabetical from the Display menu to help you work systematically. Double click on the first type of animal, bobcat, to move to its graphic frame. Look at what bobcats eat and what eats them to determine the bobcats' feeding role(s). Add each role to the net using the relation, [bobcat] plays role ___ [role]. The reverse relation ray is role played by.

Figure 3. Feeding roles of the opossum in the chaparral community. The opossum eats fruit, seeds and nuts (and thus is a primary consumer), insects and birds (and thus is a predator), and it is eaten by larger animals (and thus serves as prey).


Press the Return button to return to the alphabetical list of concepts. What is the next type of organism on the list? A centipede. Do you normally think of centipedes as being part of the animal kingdom? They are, in fact, segmented arthropods which are animals. Double-click on the concept, centipede, and describe its roles as above, based on what eats it and what it eats. Continue until you have described the feeding roles of all organisms.



    3. Connect the various roles you have introduced into the net to the concept, chaparral community. Do this by creating instances of the type, chaparral community includes organisms in role of ________________ (e.g., predator). Use is type of role in as the reverse relation ray.

Do you think your classifications are complete? One way to check is to look at each role and see how many different types of organisms function in that role. Summarize your results below, and record them on the board. Compare your numbers to those obtained by other groups.

Table 3. Number of Types of Organisms in Each Role - by Group
   Predator Prey Primary Consumer Producer Decomposer
Group 1          
Group 2          
Group 3          
Group 4          
Group 5          
Group 6          
Group 7          
Group 8          



 Exercise 6

Trophic Levels in the Community

To Do   1. Each time one organism has another for lunch, it obtains both matter and energy. Unfortunately, the amount of energy that is lost in the energy transfer process is usually much greater than the amount of energy that is transferred. Do you know what proportion of energy, on average, is transferred from one level to the next in a food chain?
    2.  The loss of energy at each trophic level places a limit on how long a food chain can be. What would you say is a typical length and maximum length of a food chain in the chaparral community?
    3.  Nearly all organisms participate in multiple food chains, but favor some chains over others. Which food chains would you expect them to prefer?

Each level in a food chain consists of one type of organism. All organisms of that type contain a total amount of matter and energy which is theoretically available to the animals at the next higher level. Biomass is the total dry weight of all the organisms present at a particular trophic level in a biological community. Given what you know about energy transfer, would you expect the total biomass at each successively higher level in a food chain to be greater or smaller than at the preceding level? Explain.



Exercise 7

Interactions in the Chaparral Community

Background 1.

Organisms have many interactions with one another and with their environment, in addition to their feeding relations. Examples of some of these interactions are given below:

  • where the organism finds shelter
  • where it finds water
  • where it finds food
  • where and how it finds its mate
  • where it gives birth to its young
  • what organisms it helps and how
  • what organisms help it and how
  • whether it is territorial and if so, how it protects its territory and from whom
  • who it competes with for food
To Do


The specifics vary with each type of organism and its specific situation. All the roles that an organism plays in the community, not just its feeding relations, are called the organism's niche. Can you describe three examples in the chaparral community in which you would expect one organism to help another? What kind of help would you expect to be provided in each case?


Suppose all the porcupines in the chaparral community were suddenly eliminated by disease. How would this affect the foxes and bobcats ?



How would the herbs and shrubs be affected by the loss of porcupines?


Suppose the ferns were to have an extremely productive year, spreading throughout the forest in a lush growth. What effect would this have on squirrels, deer and insects?


All matter is recycled through the community . For example, water that is taken in by organisms is released, sometimes to the air as water vapor or to the ground in urine and feces. The water often cycles through various bodies of soil and water and will eventually collect in the air as water vapor. In the atmosphere, the water eventually forms clouds and is returned to earth through precipitation. Plants and animals can then drink it once again. Is there a similar cycle for carbon, nitrogen, and each of the other atoms that make up living things? Explain.







Energy, however, is different. Energy passes through earth on a one-way trip. It is renewed daily, and if it weren't, life on earth wouldn't last very long. What is the ultimate source of energy for almost all living things?



    8.  How is the sun's energy used to build organic molecules?
    9.  Why build sugar? Sugar isn't even good for us! What is it used for?
    10.  Why do we say that all consumers are dependent on the producers?

Finally, do plants respire (take in oxygen and release carbon dioxide) in the same way that animals do?







Biomes of the World--Chaparral
Parker, Steve and Jane Parker. Deserts & Drylands . San Diego: Changing World. 1996

Ecoquest: Desert Edition. This is an interactive WebQuest designed for teachers in search of middle school science curriculum.

Postlethwait, J. H. & Hopson, J. L. The Nature of Life, Third Edition. San Francisco: McGraw-Hill, Inc. 1995.

Silverstein, Alvin, et al. Food Chains: Science Concepts. Millbrook Press. 1998.

Tresselt, Alvin R. and Henri Sorensen(Illustrator). The Gift of the Tree . Lothrop Lee & Shepard. 1992.

VanCleave, Janice Pratt. Janice Vancleave's Ecology for Every Kid : Easy
Activities That Make Learning About the Environment Fun
. Science for Every Kid. John Wiley & Sons. 1995.



Section D: Interdependence of Life

Grade K-2 Benchmark 1 of 2

Animals eat plants or other animals for food and may also use plants (or even other animals) for shelter and nesting.

Grade K-2 Benchmark 2 of 2

Science investigations generally work the same way in different places.

Grade 3-5 Benchmark 2 of 5

Insects and various other organisms depend on dead plant and animal material for food.

Grade 3-5 Benchmark 3 of 5

Organisms interact with one another in various ways besides providing food. Many plants depend on animals for carrying their pollen to other plants or for dispersing their seeds.

Grade 6-8 Benchmark 1 of 4

When similar investigations give different results, the scientific challenge is to judge whether the differences are trivial or sign ificant, and it often takes further studies to decide. Even with similar results, scientists may wait until an investigation has bee n repeated many times before accepting the results as correct.

Section B: Scientific Inquiry

Grade K-2 Benchmark 1 of 4

People can often learn about things around them by just observing those things carefully, but sometimes they can learn more by doing something to the things and noting what happens.

Grade K-2 Benchmark 2 of 4

Tools such as thermometers, magnifiers, rulers, or balances often give more information about things than can be obtained by just observing things without their help.

Grade K-2 Benchmark 3 of 4

Describing things as accurately as possible is important in science because it enables people to compare their observations with tho se of others.

Grade 3-5 Benchmark 1 of 4

Scientific investigations may take many different forms, including observing what things are like or what is happening somewhere, collecting specimens for analysis, and doing experiments. Investigations can focus on physical, biological, and social questions.

Grade 3-5 Benchmark 2 of 4

Results of scientific investigations are seldom exactly the same, but if the differences are large, it is important to try to figure out why. One reason for following directions carefully and for keeping records of one's work is to provide information on what might have caused the differences.

Grade 6-8 Benchmark 1 of 4

Scientists differ greatly in what phenomena they study and how they go about their work. Although there is no fixed set of steps that all scientists follow, scientific investigations usually involve the collection of relevant evidence, the use of logical reasoning , and the application of imagination in devising hypotheses and explanations to make sense of the collected evidence.

Grade K-2 Benchmark 1 of 3

Everybody can do science and invent things and ideas.

Grade K-2 Benchmark 2 of 3

In doing science, it is often helpful to work with a team and to share findings with others. All team members should reach their own individual conclusions, however, about what the findings mean.

Grade K-2 Benchmark 3 of 3

A lot can be learned about plants and animals by observing them closely, but care must be taken to know the needs of living things and how to provide for them in the classroom.


Section D: Interdependence of Life

Grades 3-5 Benchmark 1 of 5

For any particular environment, some kinds of plants and animals survive well, some survive less well, and some cannot survive at all.

Section E: Flow of Matter and Energy

Grades K-2 Benchmark 1 of 2

Plants and animals both need to take in water, and animals need to take in food. In addition, plants need light.

Grades 3-5 Benchmark 2 of 3

Some source of "energy" is needed for all organisms to stay alive and grow.

Grades 6-8 Benchmark 1 of 3

Food provides molecules that serve as fuel and building material for all organisms. Plants use the energy from light to make sugars from carbon dioxide and water. This food can be used immediately or stored for later use. Organisms that eat plants break down the plant structures to produce the materials and energy they need to survive. Then they are consumed by other organisms.

Grades 6-8 Benchmark 3 of 3

Energy can change from one form to another in living things. Animals get energy from oxidizing their food, releasing some of its energy as heat. Almost all food energy comes originally from sunlight.

Grades 9-12 Benchmark 3 of 3

The chemical elements that make up the molecules of living things pass through food webs and are combined and recombined in different ways. At each link in a food web, some energy is stored in newly made structures but much is dissipated into the environment as heat. Continual input of energy from sunlight keeps the process going.