Definetly not, and you don't need to know about calvin cycle for the MCATs I think. But incase you are curious, from what I remember calvin cycle is the same thing as dark cycle in PLANTS. So the light cycle and dark cycle are processes that occur in photosynthetic plants. And krebs cycle is completely different, and occurs during cellular respiration I believe. I don't quite remember the details, b/c this is from sophomore year bio, but i am 100% sure they are NOT the same.