If I am correct, it took less than 50 years for the human population to sky rocket
:)
Because there is more oxygen in an alveoli sac than in the blood around it, oxygen diffuses from alveoli into capillaries. <span />
All three scientists would most effectively demonstrate their concepts by using models.
Models are often used in science to provide a simplified visual representation of a certain phenomenon, making it easier to observe, understand and predict the possible future outcomes or effects of the demonstrated phenomena.