The excretory system allows animals to remove metabolic waste their bodies. Many of these substances are potentially toxic. in Mammals nitrogenous toxins like urea are expelled through liquid urine while in reptiles and birds the nitrogenous compounds are expelled as a solid. This allows birds and reptiles to use less water in the processes of metabolism.
If I remember correctly, there are two main types of transport—passive and active. Passive transport does not require energy or ATP, whereas active transport does.
Types of passive transport include diffusion and osmosis, both of which involve moving down a concentration gradient and thus not requiring energy.
Active transport moves up the concentration gradient and does require energy.
Perhaps someone who has taken bio within the last several years can correct anything I might have misstated here.
Answer:
could be A, I might be wrong
Explanation:
the other involuntary actions doesn't sound automatic
