Student Notes. Characteristics of Living Things LINK

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1 Name: Block: Date: _ LCPS Core Experience Characteristics of Living Things Student Notes OBJECTIVES Students will: Use experimental design to develop and test a hypothesis about how a living thing will respond to stimuli. Investigate the conditions to which living things respond. LINK 1. Why are experiments an important part of studying science? Background Experimental design is a series of steps used by scientists to design an experiment to collect data. The first step in experimental design is to generate a hypothesis. The hypothesis, which must be testable through experimentation, is a prediction of what the outcome of the test may be. It is often written as an If, then statement. After performing the experiment, scientists analyze the results and draw conclusions to determine whether the initial hypothesis was supported through the experimentation. If the results are not supported, scientists will often form a new hypothesis and test it. It is also important for scientists to communicate the results of their experiment to other scientists. Sharing of results often leads to new questions and answers. When the repeated experimental procedures produce similar results, the design of the experiment is reliable. In a controlled experiment, only one variable at a time is tested and all of the other factors in the experiment remain unchanged. The unchanged factors are known as constants. By changing only one factor and keeping all other parts of the experiment the same, scientists are able to determine the effect that the variable has on the experiment. Scientists conduct repeated trials to reduce experimental error. The independent variable is the one factor that is changed in the experiment. In other words, it is what you are testing. The dependent variable is the result or the data that is collected as a result of the independent variable. Often, experiments have a control group. This group is the standard upon which the effect of the independent variable is determined. The control group is untested and used as a point of reference when comparing the results of the tested groups. The information collected as a result of the testing is referred to as the data or results. This information is often shown in charts, graphs or tables to make it easier to interpret. When graphing results, the independent variable is always placed on the x-axis and the dependent variable is placed on the y-axis. Page 1

2 Lesson One: Practice Identifying Parts of an Experiment Complete the form below using the information found in the Background Information section above. Use the hypothesis below as a starting point. Title: The Effect of on Hypothesis: If plant A receives 10 hours of sunlight per day, plant B receives 10 hours of only green light per day, plant C receives 10 hours of only red light per day, and plant D receives 10 hours of only yellow light per day; plant C will grow the tallest. IV DV Trial 1 Trial 2 Trial 3 Average Control Group Plant A Plant B Plant C You will not be performing this experiment, however, this is where data would be recorded. Plant D Constants: Page 2

3 EXPERIMENT Lesson Two: Observing a Control Group 1. Question: What is the purpose of including a control group in an experiment? (Hint: Refer to the Background Information.) 2. In this investigation, you will be testing the effect of a stimulus on a worm. As a class, decide how you will set-up a control group. Lesson Three: Designing an Experiment Experimental Design Worksheet 1. Title: The Effect of on 2. Hypothesis: (if/then) 3a. Independent Variable (IV): (Include units of the measurement.) 3b. Dependent Variable (DV): (Include units of the measurement.) 3c. Constants 4. Materials: Page 3

4 5. Procedure: (numbered list of detailed instruction) LEARNING REVIEW 1. Why is it important to test only one variable at a time? Page 4

5 2. What is the difference between the independent and dependent variable in an experiment? 3. What is the benefit of using a chart or graph to display data? EVALUATION 1. Mary was testing the effect of fertilizer on plant growth. She added different amounts of fertilizer to her potting soil, and measured the growth of the plants over a two week time period. What would be the independent and dependents variables in this experiment? List at least three constants that Mary should keep during this experiment. Page 5