Answer: I believe the correct answer for this would be mutation. It has a change on DNA, but can not have ANY effect upon the phenotype.
The independent is the amount of time you do sit-ups the dependant is your heart rate because it will speed up
the control is how much effort that you put out doing sit ups
Rods are responsible for vision at low light levels so B
The right answer for the question that is being asked and shown above is that: "b. Archaeopteryx fossils share traits with both birds and reptiles."
