Gas exchange occurs by the process of .

Basic Principles of Gas Exchange

Gas exchange during respiration occurs primarily through diffusion. Diffusion is a process in which transport is driven by a concentration gradient. Gas molecules move from a region of high concentration to a region of low concentration.

Explanation:

Gas Exchange with Tissues

Gas exchange occurs in the alveoli so that oxygen is loaded into the bloodstream and carbon dioxide is unloaded from the bloodstream. ... Oxygen diffuses into the cells of the tissues, while carbon dioxide diffuses out of the cells of the tissues and into the bloodstream.

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diffusion

Explanation: Diffusion is defined as the migration of a chemical from a high-concentration area to a low-concentration area. Diffusion occurs in liquids and gases when particles migrate randomly from one location to another. Diffusion is the mechanism through which chemicals flow into and out of cells in living things.

there are so many examples for that in different areas, like biology experiment carried out in our lab recently.

here's one link:

c) 50% there are four chromosomes. after crossing over, 2 of the four have been changed. that means any gamete has a 2 in 4 chance or 50% chance of receiving the mutated chromosome.