<em>The function of skeletal muscles is to control the movement of internal organs. The skeletal muscle pulls the tendons attached to the bones.</em>
In the experiment, the independent variable is the drug amount. Experiment group is given certain amount of drug, control group is not given the drug. The dependent variable is the body fat. I think you means the control is the living environment including food and water.
Ok, think about it. Does your skin prevent germs from getting inside you?
Does your skin prevent water from leaving the body too quickly? Does your skin protect your insides from getting damaged when you fall? Do you put food on your skin to absorb nutrients, or do you put food in your mouth like a normal person?
Answer:
Cells are the basic building blocks of living things. The human body is composed of trillions of cells, all with their own specialised function.