How is darwin's theory of evolution by natural selection related to the origin of structural and physiological adaptations? Explain

Physiological and structural adaptations occur at random in population. This is because of adaptation.

In Darwin's theory, it explains how physiological and structural adaptations are being fixed within populations.

Darwin's theory of evolution states that species adapt to the surroundings by the nature of habitat, source of food, weather, thus their body structures and bodily functions adapt in order for them to survive