Oxygen.
Oxygen was fatal when organisms started using photosynthesis, this event was known as the Great Oxidation Event.
atom, molecule, cells, tissues, organ, organ system, organism
<span>1) a five carbon ribose sugar, 2) a phosphate molecule and 3) one of four nitrogenous bases: adenine, guanine, cytosine or uracil.</span>
Thyroxine is an important hormone released into the bloodstream by the thyroid gland in the body. When tyroxine is released into the blood stream, it moves through certain organs such as the kidney and liver, where most of it is changed to an active form known as triiodothyronine. Thyroxine perform important roles in brain development, heart and digestive functions, bone maintenance, controlling muscle and metabolic rate of the body.
