Teaching unit: “Microbes are important to drylands” for 4-5th graders.

My fellow graduate student Anny and I worked up a teaching unit to reach out to the younger scientists among us. We piloted it at my friend Jessica Balboa’s classroom last month and then added some final touches. Let me emphasize that we had so.much.fun! with the 20 students that attended. They also SCHOOLED me on not being lazy in how I pronounce “bosque” (the spanish word for forest which is what we call the riparian area of the Rio Grande here in ABQ); I really do know better. Anyway – please feel free to use/modify this teaching unit and PLEASE let me know how it goes so I can keep improving it for future use!

Why are soil microbes important to plants and deserts?

Target audience: 4-5th grade students

Unit Learning Outcomes

By the end of this unit, students should be able to

  1. Explain how not all “germs” are “bad”, showing the example that fungi can be beneficial to plants.
  2. Explain why it is important to “stay on the trail” while hiking to help prevent erosion because microbes help the soil stay in place.
  3. Put in order the following steps of the scientific method: ask a question, make a hypothesis, conduct an experiment, and evaluate the results.

Misconceptions:

Many students will think of microbes only as “bad germs” that make people sick or make food go bad.

Logistics and materials

Timeline:

We suggest using two separate times so that students revisit material to improve learning and retention.

Activity 1:  40 minutes

  • Introduction 0:10
  • Nutrient collection game 0:20
  • Discussion 0:10

Activity 2:  40 minutes

  • Introduction 0:10
  • Soil erosion game 0:20
  • Discussion 0:10

Materials needed:

Assessment: Some way for students to indicate “yes” or “no” without verbalizing

Activity A: 20-30 balls (tennis ball-sized, bouncy ball sized, mix of any – we used plastic easter eggs).

Activity B: Inflated balloons. Optional paper fans for creating wind.

Space:

A large open space (such as a gym) is useful for this activity so that students don’t crash into each other or desks.

Activity A: How do fungi help plants get resources?

By the end of this activity, students should be able to

  1. Compare nutrient acquisition of plants with and without root-associated fungi.

Prior knowledge:

Students may have experience with gardening or house plants. Students may have helped provide water and fertilizer.

Common misconceptions:

Plants get food from the soil (instead of via photosynthesis from light and carbon dioxide). This is really tricky to explain, especially in contrast to getting nutrients from the soil. We have concluded that because the process of photosynthesis is not the focus of this teaching unit, we will not really get into the whole “carbon source” vs. “nutrient source” detail. We make sure to say that the nutrients “help the plant grow better” so that students don’t hear us saying that that is the only thing that they need.

Introduction:

Introduce yourself

Say: “In the next two lessons we will be learning about how microbes help the environment. We will also be learning about the scientific method for answering questions about the world around us”

Ask: “Do you know what microbes are?”

  • Answer: Tiny living things. They include words like germs, bacteria, fungi/mold, and other types of small organisms.

Before-activity Assessment:

Tell students to show the instructor the red X if they say “no” and the green “O” if they say “yes”.

Practice with fun questions like “Do you like puppies?” “Do you like ice cream?” “Do you like taking out the trash”?

At the beginning, ask students the following yes/no questions and tally the number of yeses and nos. Feel free to have students discuss what they already know about these questions after they have answered yes or no. Repeat the questions at the end of the activity; if there is strong misunderstanding, revisit the subject.

Before activity After activity
Question # Yes # No # Yes # No
Do plants grow better with nutrients or fertilizer?
Are there microbes in the soil?
Are there microbes in plants?
Is a hypothesis part of the scientific method?

 

Discussion:

Ask “Do you think all germs or microbes are bad?”

  • Answer: Remind students about how some microbes make us sick, but there are also many microbes in our own bodies that help our body function.

Remind students that there are lots of microbes in the environment and while some can cause diseases to plants and animals, others can help protect the soil, and today we’re going to learn about another way that microbes are helpful.

Say: “We will be talking about one way that microbes help plants by finding nutrients in the soil.”

Ask “What do the plants in your house or garden need to grow bigger?”

  • Answer: Water and fertilizer. The instructor should be clear that plants can photosynthesize and use sunlight and air to produce most of their own food, but they still need important things called “nutrients” or “fertilizers” to grow. They can think about how they eat bread for energy, but they need to eat spinach for vitamins and minerals.
  • Write out the equation:

CO2 in the air + Water — Sunlight —>   Sugars/Carbohydrates.

Ask: “How do plants get the water and nutrients?”

  • Answer: Their roots. Talk about how the roots grow through the soil to look for water and nutrients, even though the plant itself can’t move.

Show: The photo of how much of the plant is aboveground where we can see it, and how much is in the soil where we can’t see it.

Activity:

Say: “We will use the scientific method to investigate how plants get nutrients. The first step in the scientific method is to Ask a Question. The question we will ask is “Do roots help plants get fertilizer or nutrients?”

Say: “The second step is to Make a Hypothesis or Prediction. Do you think the roots will help the plant get fertilizer or nutrients? “

Say: “The third step is to Conduct the Experiment.”

Students form groups of 3 (up to 4 but smaller groups is probably less likely to result in injury). One student is the “leaf” and the other students are the roots.

The roots have to stay touching the “leaf” student, who is not allowed to move. The goal is for the roots to give the “leaves” as much “nutrient”(balls) as they can in the given time. They are not allowed to start collecting nutrients until the instructor says “go”.

After the students are spread out in the room, the instructor spreads out the balls across the floor, making sure that some are distributed further out where students will have a hard time reaching them, and then says “GO”. Chaos ensues.

At some point, students will no longer be able to reach the more distant “nutrients” and the instructor will tell students to “stop.”

Review the three steps that they have done so far: ask a question, state a hypothesis, and conduct an experiment

Say: The next step is to Evaluate the results – do they support our hypothesis? Did the roots help the plants to get fertilizer or nutrients”

Have students gather back into one group

Introduce plant-fungal mutualisms:

Say: “In many plants, there are fungi that live in the plant roots and grow off of the roots and out into the soil.”

Show: Images of the plant vs. plant+fungi.

Say: “Fungi are much smaller so they can fit in smaller spaces in the soil”

Show: The cat stuck in the fence to the kitten moving through the fence.

Say: “In the last experiment, you were like the photo on the left, where you only had roots. In the next experiment, you will be like the photo on the right, and have fungi helping you to get fertilizer. We will use the scientific method again. First, we will ask the question: ‘Do fungi help plants get fertilizer or nutrients?’”

Say: “Next we will Make a Hypothesis or Prediction: will the fungi help the plant get MORE fertilizer than the roots alone?”

Say: “Next, we Conduct the Experiment.”

In this part of the activity, the students should form new groups of 5-6. One student is the leaf, 2-3 students are the roots, and the remaining students are the fungi. The leaf and root students have the same roles.  The fungi students must stay physically touching the roots.

The instructor re-distributes the fertilizer around the room and says “go”. Chaos ensues.

When the instructor says “stop”, the students can count up how many balls they got.

Review where they are in the scientific method – ask a question, make a hypothesis, conduct and experiment.

Say: “Now we Evaluate the results – do they support our hypothesis? Did the fungi help the plant get MORE fertilizer than the roots alone? Could the plant access nutrients that were farther away from the leaf?”

If there is time, students may repeat and switch roles. We found that it took a long time for them to catch on to how they could move and stretch to get the balls.

After-activity assessment:

Ask the assessment questions again and tally the results. Use each question to summarize the concepts.

Image library

Above ground biomass vs. belowground:

http://discovermagazine.com/2014/may/11-feed-the-world

Large cat stuck in fence:

http://www.funnyalltime.com/cat-fence/

Kitten NOT stuck in fence:

Plant with and without mycorrhizae:

http://www.appliedturf.com/organics/mycorrhizae

 

 

 

Activity B: Microbes protect the soil

By the end of this activity, students should be able to

  1. Describe how microbes protect the soil from erosion.

Prior knowledge:

For erosion, students may have experience with dust storms, haze (wind erosion), arroyos that run brown, and trails and roads that become rutted after rains (water erosion).

Common misconceptions:

The soil is dead – there is nothing living in the soil except plants.

Introduction:

Review: Ask students what they think of when they think of “microbes” or “bacteria” or “fungus”.

Say: “Some microbes make us sick, but there are also many microbes in our own bodies that help our body function. Last time we learned how fungi can help plants get more nutrients. Today we will learn about how microbes in the environment can protect the soil.”

Assessment:

Give students a card, one side with a red “X” and one card with a green “O”.

Tell students to show the instructor the red X if they say “no” and the green “O” if they say “yes”.

Practice with fun questions like “Do you like puppies?” “Do you like ice cream?” “Do you like taking out the trash”?

Then, ask students the following yes/no questions and tally the number of yeses and nos. Repeat the questions at the end of the activity; if there is strong misunderstanding, revisit the subject and re-test.

Before activity After activity
Question # Yes # No # Yes # No
Can wind or water move soil or dirt?
Can dust in the air make people sick?
Are there microbes in the soil?
Do microbes protect the soil?

 

Ask: “We know from yesterday that the soil is important because that’s where plants get nutrients. However, the soil can be broken up. What are some of things that break up and move the soil?”

  • Answer: Wind, Water, maybe they’ll think of cattle/farming. Introduce the concept of erosion, where loose soil is moved from ground cover into the air or water.

Say: “Wind erosion is when soil is moved through the air.”

Activity:

Say: “You have all have shrunk to the size of ants and that the balloons are now individual sand grains!”

Divide students into groups of 4-6 and place a pile of balloons in front of each group. The students should gather together on one side.

Say: “First we will Ask a Question. We will ask ‘Can wind move sand particles?’ Next we will Make a Hypothesis. What do they think will happen if wind blows on those balloons. Will they stay in the same place?”

Say: “Next, we will Conduct the Experiment. You will all act like the wind and blow on the sand particles across the room. Each person should watch one or two of the sand particles and keep track of whether they move or not.”

*Chaos ensues*

Say: “Next we will Evaluate the results – do they support our hypothesis? Did the balloons stay in the same place?”

Say: “Remember that this process is called ‘erosion’”

Show: Photographs of the dust storms (from Phoenix and satellite view of California, or pick photographs from the region of the world close to the students) and show how wind can move soil across the earth.

Ask: “What kind of effects that they think that the storms are having on the people, animals, and plants?”

  • Answer: Reduced visibility while driving in the storm, hard for animals and people to breathe, the plants that were growing in the soil now have nothing left to live in, etc.

Say: “There are many microbes that can live on the surface of soils in deserts. They make living crusts on the soil called ‘biocrusts’. They turn green when it rains because they can photosynthesize just like plants and they can form continuous cover across the landscape.

Show: The photo of Moab with the black biocrust across all of the soil.

Say: “Biocrusts are made up of many microbes like bacteria and fungus and lichens and mosses that are very small.”

Show: Photo of the diverse biocrust community.

Say: “Biocrusts make sticky compounds that can hold the soil together and they weave together to form a barrier to erosion.”

Show: Close-up biocrust photograph.

Say: “This time, we will investigate what happens to erosion when there are biocrusts to protect the soil. Following the scientific method, first we will Ask a Question. We will ask ‘Does biocrust protect the soil from erosion?’ Next we will Make a Hypothesis. What do they think will happen if we put a fan on those balloons but we have things that will stick them together? Will they stay in the same place?”

Say: “Next, we will Conduct the Experiment.”

Divide students into groups of 8-12 and place a pile of balloons in front of each group.

Half of the students are now biocrust organisms that are holding on to the soil. The other half of the students are the wind that will try to move the soil. The students should gather together on one side.

Have the “wind” students pick sand grains to watch and try to move across the room by blowing on them.

*Chaos ensues*

Say: “Now we will Evaluate the Results – Did the results support your hypothesis? Did the wind storm move as much soil this time as last time?”

The groups of students can switch roles or repeat these activities depending on time and enthusiasm.

After-activity assessment:

Ask the assessment questions again and tally the results. Use each question to summarize the concepts.

Image gallery:

Dust storm in Phoenix:

https://www.theatlantic.com/national/archive/2011/07/watch-50-mile-wide-dust-storm-devour-phoenix/352503/

Dust seen from space:

http://www.tucsonnewsnow.com/story/16494696/baja-california-dust-storm-seen-from-space

Many biocrust photos:

http://soilcrust.org/gallery.htm

 

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