A. You ordered an item by mail. It was supposed to arrive in 2 weeks, but 3 weeks later the package has not arrived. Why?
hypothesis:
how to test hypothesis:

Competition occurs between species when

All but one describes an effect of aging on the digestive system. a) decreased acid secretion b) decreased elasticity of stomach c) capacity to resist damage decreases d) food remains in stomach for less time

How does secondary succession differ from primary succession?