How do autotrophs obtain $CO_{2}$ and $N_{2}$ to make their food?

Single circulation,i.e.,blood flows through the heart only once during one cycle of passage through the body,is exhibited by:

Which of the following statement$(s)$ is (are) true about respiration?
$(i)$ During inhalation,ribs move inward and diaphragm is raised
$(ii)$ In the alveoli,exchange of gases takes place i.e.,oxygen from alveolar air diffuses into blood and carbon dioxide from blood into alveolar air
$(iii)$ Haemoglobin has greater affinity for carbon dioxide than oxygen
$(iv)$ Alveoli increase surface area for exchange of gases

$(a)$ Name the following:
$(i)$ Organ which stores bile
$(ii)$ Organ which produces bile
$(b)$ Name one enzyme present in pancreatic juice and give its functions.
$(c)$ What are peristaltic movements?

The blood leaving the tissues becomes richer in

$(a)$ Explain why multicellular organisms need a transportation system for carrying food and oxygen.
$(b)$ Why does an organism require an excretory system?