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.
Struggled with this earlier but because of the high altitude only some animals can live there and thrive because of the lower oxygen levels
Alpha helices and Beta pleated sheets make up the secondary structure of protein.
I believe the answer is b hope this helps
Answer:
it will be the answer B. scientists discover new elenents.