Case Study

Biblical Reference So neither the one who plants nor the one who waters is anything, but only God, who makes things grow. 1 Corinthians 3:7

Biodiesel from Microalgae During the past few decades, scientists have explored using protists to produce biodiesel fuel. Protists are a group of microscopic organisms that usually live in water or moist environments. Biodiesel Video

Designing a Controlled Experiment Scientists use scientific inquiry to investigate the use of protists to make biodiesel. They design controlled experiments to test their hypotheses. A controlled experiment is a scientific investigation that tests how one variable affects another.

Variables A variable is any factor in an experiment that can have more than one value. There are two types of variables: –The dependent variable is the factor measured or observed during an experiment. –The independent variable is the factor that you want to test. It is changed by the investigator to observe how it affects a dependent variable. Constants are the factors in an experiment that remain the same.

Designing a Controlled Experiment A controlled experiment has two groups: –The experimental group is used to study how a change in the independent variable changes the dependent variable. –The control group contains the same factors as the experimental group, but the independent variable is not changed.

Biodiesel Rudolph Diesel invented the diesel engine using peanut oil to demonstrate how it worked. Oil-rich food crops, such as soybeans, can be used as a source of biodiesel.

Aquatic Specimen Program In the late 1970s, the U.S. Department of Energy began funding its Aquatic Species Program (ASP) to investigate ways to remove air pollutants. The program’s focus shifted to using microalgae to produce oils that could be processed into biodiesel.

Which Microalgae? Microalgae are microscopic organisms that live in marine or freshwater environments, use photosynthesis, and make sugar. Scientists collected and identified 3,000 promising microalgae species, focusing on microalgae they predicted were more resistant to changes in temperature and salt content in water.

Oil Production in Microalgae Some studies suggested that starving microalgae of nutrients, such as nitrogen, could increase the amount of oil they produced. –Starving microalgae caused them to be smaller, resulting in no overall increase in oil production. Describe a Controlled Experiment for Nitrogen and Microalgae oil production.

Microalgae Growing Methods Three methods of growing microalgae are examples of different hypotheses being tested in controlled experiments. –Open Ponds –Plastic Bags –BioreactorsBioreactors List the pros and cons for each method.

Effects of Light Scientists discovered that varying light exposure affects the oil yield for microalgae. –Data from experiments showed how microalgae in well-lit environments grow compared to those grown in dimmer environments. –Scientists take light to microalgae instead of moving microalgae to light. Light rods and paddlewheels are used to bring light to microalgae.

Many Hypotheses The ASP scientists developed numerous hypotheses, because there were so many variables. –Type of Microalgae –Growth Method –Amount of Nutrients –Changes in Temperature –Salt Content –Levels of Light –Etc.

Benefits of Growing Microalgae In addition to growing microalgae for biodiesel production, there are other benefits of growing microalgae. –Microalgae remove pollutants from and add oxygen to the atmosphere. –Other products include: Human and Livestock Food Pharmaceuticals Cosmetics

The Future of Microalgae The costs of growing microalgae and extracting their oils are too high to compete with petroleum-based diesel. –The combined efforts of government-funded programs and commercial biofuel companies might one day make microalgae-based biodiesel an affordable reality in the U.S.

A.constants B.control group C.controlled experiment D.experimental group Pop Quiz Which term describes a scientific investigation that tests how one variable affects another?

A.constant B.dependent variable C.independent variable D.variable Which is a factor in an experiment that remains the same? Pop Quiz

A.constant B.control group C.controlled experiment D.variable Pop Quiz Which contains the same factors as the experimental group, but does not have the independent variable changed?