A massive increase in the growth of a specific species of algae resulted in record-breaking levels of a potentially dangerous toxin being released into the water. A researcher hypothesizes that the unusual growth of this algal species was caused by an increase in water temperature. The researcher designs an experiment to test the hypothesis. Which of the following is the dependent variable in the researcher's experiment? a. The growth of the algae
b. The temperature of the water
c. The concentration of toxin in the water
d. The different species of algae growing in the water

a. The growth of the algae

Explanation:

The researcher already knows that the over-growth of algae species results in excessive levels of a potentially dangerous toxin being released. But he/she wants to know what is causing this algae over-growth. The principal hypothesis is that the increase in water temperature is the cause of the unusual growth of this algal species. The researcher hypothesizes that the higher the temperature levels are, the more growth rate the algae will exhibit.

So in this experiment, the researcher can voluntarily modify the temperature in order to see how it changes the algae growth.

Before answering the question, let us remember a few concepts.

Now, let us analyze the options.

c. The concentration of toxin in the water. This is a dependent variable, which depends on the algae growth. The more algae present, the more toxins. However, this is not what the researcher is studying. He/She wants to know what is causing the increase in algae. So toxins, in this study, would be a secondary effect.

d. The different species of algae growing in the water . Probably this is also related to temperature and the biology of each algal species. However, the researcher is interested in a specific species of algae.

b. The temperature of the water. The temperature of THE water is directly involved in this experiment, but as the INDEPENDENT VARIABLE. The researcher will modify the temperature in order to know how it changes the algae growth. The researcher voluntarily modifies this variable, and this change provokes a change in the dependent variable.

a. The growth of the algae. The Growth of THE algae is the DEPENDENT VARIABLE. It CHANGES ACCORDING TO THE TEMPERATURE. So the change in the algae growth will depend on how the researcher modifies the temperature. We are referring to one specific algal species. This species is responsible for the toxins´ productions and is suggested to depend on temperature.

a community that experiences major changes undergoes progress

the areas around the equator