Because migration and and other seasonal movements can affect the possibility of finding a mate, stresses, that could affect offspring survival(can vary with season), and also availability of thing that are available for the offspring.
Most enzymes do in fact work on a single substrate in most cases, this is because of the enzyme - substrate specificity. Certain reactant molecules acting as substrates can only fit in the "lock" of particular enzymes and undergo a conformational change and result in Unique products to be released after the reaction has occurred.
Answer: the Earth is round.
Explanation:
