Year 8 Science · Unit 1 · Lesson 7
Challenge Worksheet
Learning Goals
Design a mini-experiment
A scientist wants to test: "Does increasing wind speed increase the rate of transpiration in a leafy shoot?" Plan the investigation below. A potometer measures water uptake by a cut shoot, as the shoot transpires, a bubble moves along a capillary tube to show how fast water is being taken up.
| What I will change (independent variable) | |
| What I will keep the same (controlled variables, list at least 3) | |
| What I will measure (dependent variable) and how the potometer helps | |
| My prediction (include the direction of change and why) | |
| How I would know if my prediction is wrong | |
| One limitation of using a potometer to measure transpiration |
1. A student records potometer bubble movement at three fan speeds (still air, low fan, high fan) and finds that bubble movement increases with wind speed. Explain the mechanism behind this result using the terms transpiration, stomata, and tension.
2. Desert plants such as spinifex grass in the Australian outback have very small, waxy leaves. Using your knowledge of transpiration and guard cells, explain why these leaf features are an adaptation to dry conditions.
Wrap Up
In one sentence, what was the main idea of this lesson?