Why do human populations change?

Because either humans are passing away quickly or there are a lot of child births (Maybe even both)

Explanation:

it depends on death rates which depends on population

Explanation:

what statement best describes the difference between the sympathetic and parasympathetic nervous systems?

the sympathetic nervous system prepares the body for intense physical activity and is often referred to as the fight-or-flight response. the parasympathetic nervous system has almost the exact opposite effect and relaxes the body and inhibits or slows many high energy functions.

producers within ecosystems are essential as they are at the base of the food chain. plants are examples of producers. they use the process of photosynthesis to capture light energy and use it to convert simple inorganic substances (carbon dioxide and water) into organic substances (glucose).