1. INDEPENDENT & DEPENDENT VARIABLE CASE STUDY
LESSON 3

2. DESIGNING A CONTROLLED EXPERIMENT
A controlled experiment is a scientific investigation that tests how one variable affects another.
A variable is any factor in an experiment that can have more than one value.
2 types of variables:
1. Independent Variable- if the factor that you
want to test. It is changed by the investigator
2. Dependent Variable- is the factor measured or observed during an experiment.

3. Biodiesel
Engines running on fuel made from plant or plantlike sources.
Ex. Oil-rich foods (soybeans) can be used as biodiesel.
Major concerns that the food crops would be used for biodiesel would cause a shortage for food crops used for food.

4. Aquatic Species Program
Investigates ways to remove air pollutants.
Coal-fueled power plants produce CO₂.
Focus of the program was to examine if microalgae (plantlike organisms) would decrease the amount of CO₂ in the air. It lead to microalgae secreting large amounts of oil.

5. MicroAlgae
Microscopic organisms that live in marine or freshwater environments.
Produces food through photosynthesis
Too much food (sugar) is produced during photosynthesis, so it is converted to oil.
Scientists chose microalgae species that were resistant to acidity, temperature, and salt levels.

6. Outdoor Testing vs. Bioreactors
Outdoor Testing were performed in small outdoor ponds.
Cooler temp. caused the microalgae to become smaller in size.
Also, Native algae would invaded the ponds.
Bioreactors- glass containers where organisms live & grow under controlled conditions.

7. Increasing Oil Yield
Scientists wanted to increase oil production of the microalgae by distributing light to all microalgae
Microalgae grows near the water surface, yet some can grow below.
Experimental Group: Light rods distributing artificial light to microalgae in the bioreactor.
Field Testing: Idea was to take light to microalgae instead of moving microalgae to the light.
Paddlewheels can also rotate microalgae to water surface.

8. Why Grow Microalgae
Microalgae helps reduce pollutants in the air, produce a valuable fuel, and add O₂ to the atmosphere.
Powerplants release CO₂ in the atmosphere and microalgae uses CO₂, water, and sunlight to produce sugar (photosynthesis).

9. Are Microalgae the Future?
Costs of growing microalgae and extracting their oils is too expensive.
Petroleum-base fuels (gas) are less expensive.