Explain the movement of ribs during inhalation and exhalation.

Inspiration (breathing in)

The diaphragm contracts and moves downwards. The intercostal muscles contract and move the ribs upwards and outwards. This increases the size of the chest and decreases the air pressure inside it which sucks air into the lungs. During normal breathing, the major inspiratory muscles produce rib cage expansion and a downward movement of the diaphragm. These movements cause the pressure around and in the lung to become negative (relative to atmospheric pressure).

Explanation:

Explanation:

During normal breathing, contraction of the major inspiratory muscle, the diaphragm, produces both rib cage expansion and a downward movement of the diaphragm. These movements cause the pressure around and in the lung to become negative relative to atmosphere.

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

here's one link:

in 1859, charles darwin set out his theory of evolution by natural selection as an explanation for adaptation and speciation. he defined natural selection as the "principle by which each slight variation [of a trait], if useful, is preserved".