Question

28. How does oxygen reach the cells in insects?

Answer 1

They have a body cavity (called a coelom) filled with blood which is kept moving around the cavity by the heart (as opposed to higher animals which have blood vessels). The blood carries oxygen around the insect's body to its cells.

Answer 2

The distance oxygen can travel down the tracheae depends on its concentration in the air. If atmospheric oxygen is doubled, theory says that it should be able to make it twice as far. According to Graham and Dudley, escalating Paleozoic oxygen levels may have helped speed oxygen transport in the longer tracheae of bigger insects. The environment itself could have opened the respiratory door for Paleozoic insects, allowing giant species to evolve.