Explain why enzymes are essential or important to maintaining
homeostasis in living things.

Enzymes are proteins that catalyse (speed up) vital chemical reactions inside the body. Enzymes will only function properly under a small range of certain conditions, such as preferred pH and temperature. If any conditions are outside their specific range then the enzymes cannot function. This could cause the organism to die. Homeostasis relies on automatic control systems that include nervous responses (nervous system) or chemical responses (endocrine system). Receptors and effectors are also needed

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The likely reason to change the gene pool in a population of chipmunks would be: A number of chipmunks die due to old age.
Gene pool in a population occurs only if there is an event that could lead to Genetic mutation. Dying from an old age is just a natural occurrence that does not change the genetic composition of an organism