guide the school football team which has just won gold medals on how to confirm whether their medals are pure gold

Why do bacteria thrive even in hostile environments

In general, characteristics that an organism survive and reproduce become more common over time. what mechanism of evolution causes this?

Amino acids contain the elements carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur. of the 20 amino acids found in humans, 11 are called "nonessential" because they can be manufactured by the body when needed. which elements in these 11 amino acids are commonly obtained from the metabolism of sugar molecules?