What is the primary role of the respiratory system in living organisms?
to use up nitrogen
to make carbon dioxide
to find hydrogen
to obtain oxygen
Young tadpoles breathe like fish.
Which structure enables them to breathe in the water?
alveoli
trachea
gills
skin
The gas exchange in humans occurs in the alveoli where oxygen enters the blood stream and carbon dioxide enters the lungs for exhalation. What major organ are alveoli located in?
the bronchi
the lungs
the heart
the brain
_____ is a gas our cells need to perform cellular respiration. Without this gas, our cells could not survive.
oxygen
carbon dioxide
helium
nitrogen
_____ are tiny pores on the epidermis (skin) of plants that control gas exchange.
