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.
A recessive trait inheritance could be more prevalent in a population than the dominant because mutation could occur because the mating does not have a wide variation causing a lethal gene or an autosomal sex link to be easily passed on the offspring
Answer:
The valves' main job is to keep the blood moving in one direction – back up towards the heart. When the valve is open, blood freely flows upward towards the heart and when the valves are closed, blood cannot flow back
White blood cells (D) aid in the immune system to fight infections.
