Plant and Animal Interdependence

Plants and animals form a complementary, self-sustaining loop of gas exchange in the biosphere. During photosynthesis, plants absorb carbon dioxide through their stomata and release oxygen as a by-product; this oxygen diffuses into the air and is inhaled by animals, including humans, whose lungs pass it into the bloodstream to be delivered to every cell. Inside the cell, whether plant or animal, oxygen is used in cellular respiration to break down food and release usable energy, and carbon dioxide is generated as a waste product that plants can take up again for photosynthesis. The key structural difference is that animals possess a dedicated respiratory system (nose, lungs, blood) built specifically to move oxygen from the environment to their cells, while plants have no such specialised transport system -- gases simply diffuse directly into and out of cells through stomata and other surface openings, because no plant cell lies far from the outside air. Despite this structural difference, the biochemical stages of cellular respiration itself a …