Question

question 44
in the section \investigating life: does natural selection maintain cystic fibrosis?\, what is the dependent variable in the figure?

• the number of defective copies of the cftr gene in mice
• the number of defective copies of the cftr gene in humans
• the amount of fluid in the intestines
• whether or not the subjects were exposed to cholera toxin
• whether or not the subjects were exposed to vibrio cholera bacteria

Explanation:

To determine the dependent variable, we analyze the graph: the x - axis is "Fluid accumulation ratio (mass of fluid/mass of intestine)", and the y - axis is "CFTR gene in copies" (with categories like Both faulty, One faulty (one normal), Both normal). The dependent variable is what is being measured (the outcome), which is related to the amount of fluid in the intestines (represented by the fluid accumulation ratio). The other options: the number of defective CFTR gene copies are independent variable categories (y - axis groups), and exposure to cholera toxin/bacteria is not shown as a variable here.

Answer:

the amount of fluid in the intestines