Lesson Summary Throughout this unit, students will be learning how to design controlled science experiments.  These experiments include variables, conditions that change, as well as controls, conditions that remain constant.  Students begin thinking about the ways in which a good experiment is like a fair test, when one thing is tested at a time while everything else remains the same.  Students are introduced to Wisconsin Fast Plants (Brassicas) that are used for these experiments.  The class also learns about this plant’s special requirements for growth and development. Teacher Background Students will be using Wisconsin Fast Plants to design controlled experiments.  These plants are particularly suited to this because they are specially bred to be compact, hardy, very fast growing, and prolific seed producers.  To develop experiments, students will need to first identify the Brassica plant’s unique requirements for growth and development – the conditions under which these plants grow best.  These include the amount of light needed, the amount of water needed, the amount of fertilizer needed, and the appropriate temperature, among others. These conditions are called variables.  During a scientific experiment, one variable is changed in some way.  For example, if the Brassica plant requires continuous light, changing that variable might mean that’s you try depriving it of light for extended periods of time.  You would then be testing the effect that light has on the plant.  In order to guarantee that light and only light is being tested, all of the other variables – temperature, amount of fertilizer, amount of water – would remain unchanged. This set-up, in which one variable is changed and all the rest remain unchanged, is a controlled experiment.  The variables that remain constant are the experiment’s controls. Compare a controlled experiment to a race, which is nothing more than a “fair test.”  In order for a race to be fair, all participants must start from the same place and end at the same finish line.  Other important variables are the time that the runner begins the race and the length and condition of the path.  If all of these variables are held as constant as possible, the variable that is tested is the running ability of the racers.  Presumably, the person with the most running ability wins. Being able to identify variables is an important skill in science.  It implies that you are able to look at a situation in terms of all of its component parts, understand how each part might change, and speculate how that change might affect the whole.  In some cases, students may conduct an experiment that produces no change.  Students may feel their experiment was a failure, but that is not the case.  Instead, students have found that changing the variable in that way has no great effect on the plant.  This is an important and valid finding. The components of a good experiment are as follows: The researcher develops a good plan and follows it. The topic chosen for the experiment is interesting and worth doing. The researcher gathers information on the topic either through reading or talking with experts. The researcher makes careful observations over a period of time. The researcher keeps records – accurately, honestly, and regularly. Something is measured. After collecting data, the researcher draws a conclusion based on the data. The findings of the experiment are communicated. Listed are the conditions that Wisconsin Fast Plants need to grow best.  Manipulating these variables will form the basis of the students’ experiments. Ideal Growing Conditions Probable Consequences of Varying the Condition 40 – watt, cool, white, fluorescent light Other types of lights produce too much heat and scorch the leaves. A continuous supply of water. Too little water leads to wilting and death. Temperature between 70 and 80 degrees F Between 60 and 70 degrees F, the life cycle slows down by several days.  Below 60 degrees F, most seeds fail to germinate. *24 hours of continuous light Any less light results in a slower life cycle, taller and skinnier plants, and fewer flowers and seeds. *3 fertilizer pellets per cell Under-fertilizing results in a nutritional deficiency, which will produce stunted plants, pale leaf color, delayed flowering, and fewer seeds.  Over-fertilizing results in increased flower, pod, and leaf production; dark green leaf color; delayed flowering; and stress due to the high level of salts (fertilizer) in the soil. *1 plant per cell Competition for water, nutrients, light, and air results in weaker plants and a smaller yield of seeds. *Cross-pollination Unless blossoms are cross-pollinated, no viable seeds will be produced.  *Indicates that this is a good condition to vary for an experiment. Set-up/Management Tips Prepare 2 pieces of chart paper.  Label one sheet “What we know about how to carry out an experiment” and the other “What we know about flowering plants.” Students will need the Student Activity Book to read pages 4 and 5 on background information on the Wisconsin Fast Plants. Students will also need their science journal to draw and label the parts of a flowering plant. If students have having difficulty understanding a “fair test,” discuss the situations on page 12 of the teacher’s manual. Xerox or post the calendar of the Life Cycle of a Normal Brassica Plant for students to refer to throughout the unit as a guideline. Literacy Support Scientific Vocabulary The following words are key vocabulary words that will be introduced in this lesson and reinforced throughout the unit: Controlled experiment, controls, fair test, variable, Wisconsin Fast Plants, Brassica.