Explain the functions of the muscular system to a child

The main function of muscular system is movement, but also stabilization

As you have probably guessed, the main function of the muscular system is movement, but it also helps stabilize our joints, maintain our posture and generate heat during activity. Movement of our body can be voluntary and controlled by the skeletal muscles, or it can be involuntary and controlled by smooth muscles.

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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".