A student is investigating how substrate concentration affects the rate of an enzyme-catalyzed reaction. Which three variables should be kept constant in the setup of the student's investigation.

good one: produce hormones that plants grow.

bad one: the problem with organic matter is that while plant nutrients are needed for crop growth, they can also stimulate excessive growth of the wrong plants – mainly, algae.

the answer is

c. parental

he forelimbs below belong to four species that descended in a direct line from the ancestral mammal shown above. of the four descendants shown, which species most likely appeared earliest in evolutionary history?