Guiding Question: What types of adaptations do plants need for survival in a cedar glade?
Critical Content: Students will be able to describe the adaptations that are required and present in plants that are found in the cedar glades.
At the end of this activity, students will be able to:
When settlers first arrived in the mid-south, they observed locations where there were no trees. They named these locations "glades". Approximately 43 acres of these rare cedar glades are present in Stones River National Battlefield. Cedar glades are, as expected, treeless because of very shallow soils. Many of the plants within the glades are endemic, which means they are found exclusively in cedar glades. This plant life is mostly composed of non-woody plants. Plants have adapted to these extreme micro-climates.
Cedar glades consist of extreme climatic conditions. Winter temperatures in glades are analogous to those of neighboring forest; however, summer temperatures are frequently 10 to 30 degrees higher. Thin glade soils tend to remain waterlogged throughout much of the wet winter and early spring, but dry rapidly during the summer. Then the glade becomes desert like.
Glade plants, like many desert plants, have unique ways of surviving hot, dry summers. Plants that grow in thin soils have very shallow roots and are small. Several glade plants create flowers early in spring and release seeds before the harsh conditions develop. Others plants produce a lot of seeds and a have a life cycle that is very quick. Several glade plants are perennials. They have abundant belowground stems or bulbs that store food. Still others stay alive by having extensive root systems that absorb water from soil under rocks or by storing water in leaves. Other adaptations consist of a plant’s inability to be used as a food source for animals or the manufacture of chemicals that prevent the growth of other plants.
sponges (1 for each group of three students)
balance scale (1 for each group of three students)
- Write a list of some of organisms that live in the cedar glade on the board. The teacher will review that all life is dependent upon sunlight and that living things interact with each other in diverse methods to acquire energy either directly from the sun or by consuming organisms that acquired energy from the sun. Students will identify the ecological role for each of the organisms listed on the board by listing a P (producer), C (consumer – what type: herbivore, carnivore, omnivore), D (decomposer), S (scavenger).
- Ask the following questions: What are these organisms? Where are they found? What is the relationship of these organisms to each other? How do you determine the relationship of these organisms to each other?
- Have the students read Stones River National Battlefield Geologic Resources Inventory Report (page 17-18).
- Distribute the Cedar Glade Species List.
- Each student will choose one cedar glade organism to represent. They will write the name of the organism they chose to represent in large letters on one side of a large notecard. Students will tape the notecard on the front of themselves for others to view.
- Organize the students in a circle.
- Begin by standing in the center and say, "I am the sun and represent the energy of sunlight and I am passing my energy to (teacher picks a glade plant) which is a producer. This plant makes sugar from the energy of sunlight and the fruits and tissues provide food for other organisms." Hand the student with that organism the ball of string. NOTE: Inform the students that are given the ball of string to hold the string firmly before tossing it to another student.
- The student with the ball of string is a producer and will start the web. The student must choose an organism that will have a relationship with the plant, i.e. eating pollen, nectar or consuming or decomposing the plant. After the student announces their choice, the student then throws the ball of string to the student that represents that organism, if at all possible to the other side of the circle. That student catches the ball of string. The string web will progress as students find connections to all the organisms in the circle.
- As the students are announcing their choices, have them describe the relationship between the two organisms.
- Continue until all students in the circle have been involved. It is also acceptable for some students to have more than one relationship (holding more than one string).
- The students will be standing in a circle with string connections to each other. To show the idea of interdependence of all living things, have the students close their eyes. Describe how you will initiate a 'tug' and when a student senses a tug on their string; they are to tug in return. All students in the web will feel a tug so there will be a continual pulse of tugging moving about the web.
- Ask the students: What does the 'tug' signify? Did some students obtain a 'tug' from more than one organism? Why? How are the diverse organisms in the web connected to each other? How are they linked to the energy of sunlight if they are not photosynthetic?
- Students will demonstrate an understanding of the Web of Life concept by diagraming a food web using the list of organisms found in a cedar glade.
- Ask the students what are the requirements for survival for plants? Write them down on the board.
- Talk about some of the challenging conditions that are present in cedar glades such as: shallow soil, dry conditions, limestone bedrock near the surface or exposed, and little tree growth.
- Ask the students what types of adaptations would a plant need to be able to survive in a cedar glade? Focus on the ability to hold water during dry conditions.
- Separate students into groups of three. Give each group a sponge saturated with water and a balance.
- Explain to students that the sponge signifies a plant living in the cedar glade with a restricted supply of water. It is each group's job to make an organism that is capable of conserving as much water as possible. Students can use any of the materials on the "supply table." Encourage students to be imaginative with their plans. It is essential that the "organisms" are uncovered in the air for quite a lot of hours throughout the day.
- Next, students should design their strategies and write them down - What materials are they going to use to assist the sponge to save as much water as imaginable? When finished, they must get their plans accepted by the teacher. Encourage students to use their previous experiences with these materials to design their strategy.
- Have students complete their "plan."
- Have students weigh their sponges over the next several days. Record these in a data table.
- Pose the following questions to the class: Which "plans" seemed to work best? Why? What evidence do you have? Which "plans" didn't work well? Why? What evidence do you have? How does this activity help us learn about plant survival in the cedar glade? What types of things do you think plants have that help them survive in dry places?
- Facilitate a class discussion around these questions. It is essential for students to use evidence to back up their claims. Be sure to ask "why" if they just state an answer. Most dry climate plants have developed behavioral and physiological mechanisms to handle the shortage of water. Students might mention: heavy outer layers, very extensive roots that help obtain moisture at the water table, spines for protection, or no leaves.
- Have students diagram their sponge and label the adaptations that would help the organism to survive a dry environment.