Help me, my brain's under a rock and due in 5 minutes, late work

What would happen to the nutrients in an ecosystem if decomposers, such as bacteria, didn’t exist there?

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

Why do we perceive objects as retaining their brightness under different lighting levels?