In this lesson students develop their scientific inquiry skills through planning, organising and conducting a practical investigation into the structural features that help conserve water.
View the video Plant adaptations and discuss the different adaptations that plants have that enable them to survive in different environments.
Revisit the physical conditions of deserts and semi-arid regions and ask students to suggest adaptations plants have to help them survive in these regions. Ask students what might happen to these plants if the environmental conditions change.
Organise students into cooperative learning teams and provide each team with a variety of different leaf types (from Australian indigenous plants and from non-Australian plants), hand lenses and light scopes or microscopes. Ask students to identify what is the same about the leaves and what is different.
Ask students how they think the features of the leaves of the plant relate to the physical conditions of the environment in which they live.
Teacher note: As students are working with plant samples be aware of possible allergies to some leaf types and ensure students wash their hands after handling the material.
- Explain to students that they are going to work in cooperative learning teams to plan and conduct an investigation that simulates a water conservation technique used by some plants.
- Organise students into teams and present them with an investigation topic. (This could be a teacher choice from the list below or students may be able to develop their own investigation, depending on their level of confidence.) Possible ideas for investigation:
- What difference does the waxy coating on leaves make to water retention? Use petroleum jelly on the underside of leaves to simulate the waxy side of leaves.
- How does the shape and size of leaves impact on water retention? Use kitchen sponges to represent leaves and determine how quickly water evaporates.
- Do curled leaves help retain water? Use pieces of kitchen sponge to represent the curled and uncurled leaves.
- How much water do different types of leaves release? Use plastic bags over leaves to collect water given off by the transpiration process. Which leaf types release the greatest amount of water? What conditions impact on the amount of water lost from leaves?
- Give each team a copy of the Investigation planner and explain the different sections to them. Provide students with the time necessary to set up and conduct their investigations.
- Ask students to complete questions 1 and 5 of the planner and then share predictions with the class.
- Ask teams to discuss how they are going to set up their investigations. How will they ensure the test is fair? What does this mean? What will it look like during the investigation? What variables are they going to have to consider? Meet together as a class to discuss the possibilities and to highlight the need for fair testing.
- Ask teams to develop their procedure and record how they are going to complete the investigation. Ask them to complete questions 2, 3 and 4 of the planner.
- Students conduct their investigations.
Once the investigation is complete, give students time to record and present their results and conclusions and complete questions 6, 7 and 8 of the investigation planner.
Meet as a class to share conclusions and discuss the success of the investigation and ways students could improve or further develop the investigation.