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Experiments
SUMMARY: This lab is designed to provide students with a laboratory experience with sea urchins under experimental conditions. In this investigation we will do the following:
  1. Choose a problem or question for study.
  2. Propose a hypothesis.
  3. Devise an experiment to test the hypothesis.
  4. Prepare necessary materials and conduct experiment.
  5. Record observations, analyze results and propose new hypothesis.
  6. Propose additional experiments to test new hypothesis.
High Difficulty
Timing
Background
Materials
Procedure
Math
Implications
Evaluation

Timing

  1. Introduce the topic the week before you plan to begin experiments. 30 minutes
  2. Require students to research possible topics for their experiments. homework
  3. Assign lab plan to include problem, hypothesis and procedure. homework
  4. Review problem, hypothesis and procedures for each lab group. 5-10 minutes/group
  5. Set up experiment, gather materials and make solutions. by arrangement with each group
  6. Conduct experiment. 1-5 days, Day 1 = 45-50 minute period, succeeding days a part of each period.

Background

The single biggest producer of toxic waste in the USA is the common house hold, producing more waste than industry, universities, schools, etc. Most of this waste ends up in land fill where it finds its way into our water supplies. Until recently 3/4 of all used motor oil ended up in landfill. Motor oil is toxic from its organic components, but more importantly from the quantities of highly toxic cadmium and vanadium metals that have worn off of engine components. Detergents, bleach, paints, even salad oil can be hazardous if in high enough concentration and in the wrong place. Most of these toxins end up in our streams, ground water, and water supplies and eventually into the oceans. Once in the oceans the toxins work their way up the food chain in ever increasing concentrations until the ultimate consumer eats them (US!). What goes around comes around!

It is estimated that a very high percentage of pregnancies in humans end in the first weeks of development before a women even realizes that she is pregnant. In sea urchins, development can also go awry and environmental factors appear to play a large role. Pollution from a wide variety of sources can interfere with normal development, as can temperature, lighting, oxygen levels, pH, and agitation. The Environmental Protection Agency, in fact, uses sea urchin development as a measure of environmental pollution in a locality.

Important: if you are seriously considering doing experimental work with sea urchins, finding the minimum sperm to egg concentration is important. There are many factors affecting fertilization, but you will miss many of these effects if the sperm concentration is too high. A high enough concentration of sperm can sometimes fertilize an egg that would not normally fertilize, by counteracting or overcoming the experimental environmental conditions. As mentioned earlier, if the sperm concentration is too high you will get abnormal development because of polyspermy, which may be an effect independent of what the experiment was about. see the Sperm Dilution lab.

Also, students need to understand the concept of dilution of their "toxics". See Simple Dilution and Simple Dilution 2.

Materials

Procedure

This is highly experimental and can be a lot of fun. It is best if the students design their own experiments within the available materials. Give them a few days to come up with ideas and discuss it among themselves. You could assign groups to different environmental categories such as light, temperature, toxins, etc. to illustrate a variety of influences.

Possible effects to look for:

Careful use of controls is essential. Concentration of the pollutants is important. Best if the concentration can then be related back to something in their own lives.

Example of a possible experiment:

  1. Start with the concentration of bleach in a wash load and do a serial dilution until no effect is observed. (concentration on bottle diluted into washer load)
  2. Check with your local water company and ask what the waste water volume produced in your community is for a typical day.
  3. Relate this to your observed results. How much bleach would be needed to make your communities waste water toxic due to bleach)
  4. Reports should include drawings, tables or graphs, any math used to determine concentrations and dilutions.
  5. Most of the experiments can very easily be expanded to an independent research project.

Similar scenarios can be developed for other environmental effects. These might include:

See lessons on Simple Dilution, Simple Dilution 2 and Sperm Dilution

Math

Every report will be different, but almost all will require math skills, especially in regards to dilutions of toxins.

Implications

You could easily spend an entire class period "debriefing" from this lab. The closer the experiments are to materials they will encounter themselves the easier it will be for them to see the implications. Almost every town has an industry of some sort. Using the possible pollutants from that industry can really open eyes. (even a tourist town uses gasoline, oil, detergents, etc.).

Evaluation