Why is the theory of evolution so critical to our understanding of the history of life on earth? explain how evolution proceeds by natural selection and what happens to dna that allows species to evolve?

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when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.