1. Introduction to Biodiversity Unit.

Have students complete the Michigan Biodiversity Blitz student activity. Students should be given about 10 minutes to circulate amongst one another obtaining as many answers as possible. Unless you have a very small class, each student should sign a particular paper only once. Following the activity, lead a discussion about student responses.

What makes Michigan a special place to live? Refer to the list provided at the end of Lesson 1 (and/or PowerPoint presentation by the same name, found on the MEECS Ecosystems & Biodiversity CD) to stimulate a discussion about what makes Michigan a special place to live. Also ask students for ideas of how Michigan is not different from other states. [For example, Michigan has more coastline along the Great Lakes than any other state.] (Skip this part if already completed in Lesson 1.)

2. Create a model of a Michigan forest ecosystem.

Have students sit in a circle (on the floor or in chairs). Ask students what living things might be found in a Michigan forest. Distribute one Forest Ecosystem Picture Card to each student. (The teacher should wear one, too.) Each card depicts a living thing from a forest. The card should be hung around the student’s neck so that other students can see it. Ask each student to describe his or her card, i.e., “who they are.” Have them give one unique detail about themselves.

Note: You may wish to point out that the ratio of producers to consumers in this model is inaccurate. In reality, there are far more producers than consumers in any balanced ecosystem.

Ask students what else is found in a forest ecosystem. Students should be able to identify non-living things including sunlight, water, air, soil, and nutrients. The students all represent different living things in an ecosystem that together make up a community. Review that a community of living things, together with the sunlight, water, air, soil, and nutrients, make up an ecosystem.

3. Illustrate interdependence within a Michigan forest ecosystem.

Tell students that this activity uses string to illustrate how different living things depend upon one another within an ecosystem. Model the activity by holding the ball of string and stating what organism you are (e.g., squirrel). Then, holding onto the end of the string, pass the ball to another organism, explaining the connection. For example, you might state something like “I am a squirrel. I depend on the beech tree for food and shelter.” Each time, before the ball of string is passed, the student must explain the rationale for the connection. It is helpful to make sure that the entire group understands and agrees with the rationale before moving on to the next person. Direct students to establish a connection with everyone in the circle, so that no organism is left out.

What pattern does the twine make? When you have every organism connected, direct the students to slide back, pulling gently so the string becomes taut, and then keep still. Ask the students to observe the complex pattern they have created, which represents the interconnections between organisms that occur within a community and is sometimes referred to as the “web of life.” Have students identify examples of interdependent relationships within the ecosystem. For example, a flower may be dependent on a hummingbird for pollination, while the hummingbird is dependent on the flower for food.

How does the classroom web compare to the web of life that actually exists in a forest? While the classroom model does illustrate interdependencies that would be found in an ecosystem, students should also observe that in reality, a Michigan forest is home to thousands of different kinds of plants, animals, and microbes.

4. Demonstrate the effect of natural or human disturbance in an ecosystem.

Designate one student to start tugging (gently!) on the twine. Any student who feels a tug should respond by also tugging, which should continue until every organism within the web is tugging, and the entire web is shaking. Explain that when the population of even one species is affected because of a natural or human-caused disturbance, other interdependent populations will also be affected as a result, often causing some populations to decrease and allowing others to increase. While some species may be harmed by a disturbance, others may actually benefit.

What would happen if one species was removed from the ecosystem? Suggest that mosquitoes (or another organism) be eliminated, because many people don’t like them. Have the student with the mosquito card let go of the string. After the string is released, immediately ask if anyone felt the tension in the string change when the mosquito dropped out. [Several, including the birds and frog should say yes.] Ask those affected by the loss of the mosquitoes to say how they were affected and whether the population of the species they represent would increase or decrease. Have these “affected” students drop the string. Repeat the procedure until everyone has dropped the string. Discuss how even the slightest change may eventually be felt by all species within an ecosystem.

5. Demonstrate how loss of diversity can weaken ecosystems.

What happens when we reduce the number of species living in an ecosystem? Explain that during the early 1800s, Michigan was almost entirely forested (95%), and settlers cleared away many acres of forests because they wanted to farm the land or sell the trees. Today, about half of Michigan is forested, while the other half is mostly farmland or urban areas where people live. Discuss which of the forest species would be able to live in an urban or farmland area. [Least likely: beech tree, bunchberry, black bear, box turtle, salamander, wolf, porcupine, red-shouldered hawk, ring-necked snake, tiger beetle, white-breasted nuthatch, wolf spider, and oyster mushroom.] Have those students who would not survive take off their cards and partner with one of the surviving organisms for the remainder of the activity.

Note: In order to guarantee a noticeable effect, 30-50% of the species should be eliminated.

Discuss the following questions:

How does the number of species in this “altered” ecosystem compare to the forest ecosystem? [The forest ecosystem had more species. In reality, Michigan hardwood forests tend to be more diverse than residential and urban areas.]

Will the lower diversity of species in this “altered” ecosystem make any difference if there is a sudden change in the environment (such as introduction of a disease or pest)? [Allow students to make predictions.]

Have the remaining organisms start over with the yarn and create a new web. Make sure students realize that this web is much less complicated. Repeat the same procedure as in step #3. Were the effects of losing one species more visible when the SAME ecosystem contained fewer or more species? [Fewer.] Populations within disturbed ecosystems like this one are generally more vulnerable to sudden changes in their environment, because they usually have fewer checks and balances.

6. Tying it all together: Introduce the term biodiversity and discuss its importance.

How many different species of plants and animals do you think live on Earth? In the United States? In Michigan? Using the Michigan Biodiversity transparency master, introduce the fact that scientists have so far identified around 1.4 million species. (This number represents only the species that have actually been studied. These tend to be the larger, easier-to-see species. Scientists estimate that there are actually between 10 and 100 million species on Earth. Millions of species have yet to be discovered, especially smaller species living in tropical and ocean environments.). In Michigan alone, scientists estimate there are 18,000-23,000 different species.

Introduce the term biodiversity, which refers to the variety of life on Earth. It includes all of the different plants, animals, and microorganisms on our planet. It also includes the diversity of ecosystems (such as forests and wetlands) around the world as well as the diversity of genetic information (what makes every species and individual unique) within all living organisms.

Does it really matter if one species disappears or becomes extinct? Can losing just one species really affect an ecosystem? Introduce the idea that the loss of some species has a greater effect than others. For example, the loss of a carnivore (e.g., gray wolf) from an ecosystem generally tends to have a greater effect than the loss of an herbivore.

Why is biodiversity important? Have students brainstorm and share ideas for why they think biodiversity is important. You may also wish to have students refer to the Michigan Ecosystems: What Have They Done For You Lately? unit poster, provided with this unit. For detailed information, you may also refer to the Background Information section in this lesson.

Some example reasons may include:

• Ecosystems and the biodiversity within them provide services that all of life on Earth depends on. [e.g. air & water purification, flood & erosion control, pollination, decomposition, seed dispersal, decomposition, photosynthesis, etc.]

• Yet-to-be-discovered species may provide potential sources of new medicine, food, or other products.

• Biodiversity provides inspiration to humans, and is evident in the world’s artwork, religions, literature, and music.

• Intrinsic value—all things have value simply because they exist.

• Our economies depend on the services and products provided by ecosystems and the biodiversity within them.