Biodiversity: What's the Big Deal?
Lesson 8 of 9
Objective: SWBAT explain why maintaining biodiversity is important to the health of an ecosystem and develop suggestions for maintaining biodiversity.
This information corresponds with check in 4 of the spider biodiversity quest.
It is challenging to find ways to inspire student thinking about topics without directly telling them what they need to know or what exactly they have to do. It is worth taking this approach, however, as it allows (forces?) students to chart their own course and adds variety to the answers students develop. This reinforces the idea that there are many ways to complete a task and that students need to determine the path that makes the most sense to them.
The PowerPoint on the Kudzu Vine is my attempt at prompting student thinking about the importance of biodiversity. The kudzu vine is an invasive plant that has begun to destroy large plots of land in the southern United States and other parts of the world. The ‘Vine that ate the south’ Discovered in Canada article has a lot of interesting facts about the issue and makes a good supplementary article for students to read following the PowerPoint discussion.
I use the Kudzu Vine as the focus of the discussion because it is similar to an issue found in the book series The Uglies by Scott Westerfeld in which a beautiful rare plant was genetically modified to be more hardy and it ended up growing wild to the point that it starved out every other plant including food crops. This caused the leaders of society to drastically alter our way of life. If you haven't read this series, I strongly recommend it as there are a lot of science connections you can make throughout the series.
The article Coming Soon to a Habitat Near You: From Pythons to Pine Beetles, Alien Wildlife Is on the Move by Bryan Walsh was recently published in Time Magazine's 100 New Scientific Discoveries. It is excellent at explaining the threat that invasive species pose on ecosystems and is worth investing some time having students read and respond to this information.
One point about biodiversity that I want students to fully understand is the connection between high biodiversity and the health of the ecosystem. The Biodiversity Activities on Access Excellence is great for demonstrating this idea in a way that middle school students can understand.
This activity focuses on the spread of disease through two different environments: one with high biodiversity and one without. The goal of the activity is for students to recognize that disease spreads much further and more quickly through an ecosystem with only one type of plant (mono-culture) than it does when there are a variety of organisms (diversity). This is because in a mono-culture the plants are typically close together (think of a corn field), allowing disease to spread quickly through the population. In an ecosystem with high diversity, there are more organisms between any two plants, which slows the spread of disease and increases the likelihood of containment to just a few individuals.
In this activity students are given a card; one side of the card is labeled as Douglas Fir, representing a mono-culture, and the opposite side of the card is labeled with a wide variety of tree species including Douglas Fir, Noble Fir, Western Red Cedar, Vine Maple, Western Hemlock, White Fir, Lodgepole Pine, White Pine, Bigleaf Maple, and Western Dogwood.
I begin by showing students the following image and have them count how many different types of plants they can see. In their journals, I ask them to quietly write if they believe this is good, bad, or has no effect at all on an ecosystem and to explain why they think so. You may choose to have some students share their answers but since it is more to activate student thinking it is not necessary.
- Give all students a card and have them keep the side labeled Douglas Fir visible.
- Each person is to meet and shake hands with 5 other people and write their names on the card.
- When each student is done, they go back to their original seats but remain standing.
- I symbolize the disease by shaking hands with 1 student. That student must sit down (sadly, they are dead) and they must read the names on their card. As those names are read, those students also sit down as they were infected as well.
- Each of those students should read the names on their card and any student still standing must sit when their name is called. This continues until almost all students are sitting.
- Ask students to explain why the disease spread so fast (they are all the same type of tree so their similar genetics are affected by the disease in the same way)
- Ask students to identify places in which this type of disease spread may actually happen (any type of crop; you may choose to elaborate on any example such as Hawaii's banana bunchy top virus)
- Students now flip over their card (this should show a much larger variety).
- Explain to students that some forests, specifically old growth forests, have a variety of trees.
- Students repeat the handshaking activity, being sure to record the names of the students they interact with on their card.
- I again symbolize the disease by shaking hands with a student. This time, only those students that are the same variety as the diseased tree that touched them will sit down. Different variety trees don't sit (die) even if they are touched by a diseased tree.
- Most students will remain standing (alive).
- Ask the students to explain why the disease did not spread this time (genetic/biological diversity lessens the impact of disease spreding)
I really like the following questions from the Access Excellence lesson. I use a variety of strategies when giving students questions like these to answer. Sometimes I give students the entire list and have them select any two or three to answer. Because all of these questions are worth considering, I create papers with two or three questions on them and distribute them among the student groups for the students to answer and use their responses as a discussion starter the following day. The resource Post Activity Analysis Questions is set up to print and cut on the line for this method.
Follow up questions (refers to the second of the card simulations)
- What does biological diversity mean?
- Why didn't all the different trees get the disease? (hint - genetics)
- Why didn't the disease spread as fast among the Douglas firs as it did in the first simulation?
- In which forest would you need to use more chemicals to control disease: the Douglas Fir forest or the more diversified, old growth forest? Why?
- Summarize what this simulation symbolized.
- Which forest would have more diversity of wildlife (Douglas Fir or old growth)? Why?
- a. If you cut down the variety in a piece of forest you owned and replanted with 1 type of tree, what will happen to much of the wildlife that was adapted to that forest? (Hint: they cannot just move elsewhere. If other habitats are good, they will probably be near carrying capacity already.) b. Will this fate happen to all the wildlife? Explain.
- Many species can only live/reproduce in 1 type of forest. The spotted owl is an example - it can only live and successfully reproduce in old growth forests(big, old cedars, hemlocks, etc.). If these old growth forests are cut down, it's unlikely this owl will survive. Environmentalists call it an "indicator" species." What does this mean? Why be concerned about 1 species?
- Growing one plant, as is the case of growing only Douglas fir, is called monoculture. Give an example of growing one plant a) in your home (obvious )
b) in farms
- Why would you need to use more insecticides in monoculture? Is this good or bad?
- If you wanted to help wildlife, what would you with regards to the landscaping of your own home?