Together, respiration and photosynthesis keep the levels of carbon dioxide and oxygen in the atmosphere .

fairly constant

Explanation:

Respiration produces carbon dioxide which is used by plants for photosynthesis reducing the amount of carbon dioxide in the atmosphere

the offspring would all be white. if the parents are both white flowers then they have the genotype rr, which when crossed results in an all white punnet square.

enzyme active site and substrate specificity

enzymes bind with chemical reactants called substrates. there may be one or more substrates for each type of enzyme, depending on the particular chemical reaction. in some reactions, a single-reactant substrate is broken down into multiple products