Do algae grow more in water with a high salt content than in water without salt?

• He used six tanks, all with the same volume of water and kept at a constant temperature of $20^\circ\text{C}$.
• The independent variable is the salt content: three tanks had high salt content, and three had no salt.
• An equal amount of algae was added to each tank, and the growth period was consistent (two weeks).
• The dependent variable measured was the amount of algae in each tank after two weeks.

This setup allows Lester to compare algae growth under different salt conditions while keeping other factors constant.

Let's evaluate the options:

• Do algae grow more in water with a high salt content than in water without salt? This question directly relates to the independent variable (salt content) and the dependent variable (algae growth) in Lester's experiment. This is the question his experiment is designed to answer.

• Is the growth of algae affected by the temperature of the water in a tank? Lester kept the temperature constant at $20^\circ\text{C}$ for all tanks. Therefore, his experiment does not vary temperature and cannot answer questions about its effect on algae growth.

The correct option is:

• Do algae grow more in water with a high salt content than in water without salt?