Because two organisms one with the trait and one without could make an organism which would cause variation
Putting a liquid in a freezer will turn it into a solid/ice. Boiling water will turn the water into gas. Melting an ice cube will turn into liquid because of the heat.
Good coronary circulation nourishes the heart and reduces the risk of a heart attack. Coronary arteries supply blood to the myocardium and other components of the heart. They originate from the left side of the heart at the base of the aorta. The heart muscles needs oxygen-rich blood to be able to carry out its functions.
the temperature of mercury is not regulated and the atmosphere easily floats away while being replaced with solar wind .
Mercury has a thin atmosphere.
