Matters: composition of organisms - anything that takes up space and has ma: exists in many forms. Elements and compounds: matter is made up of elements, element - a substance that cannot be broken down to other substances. Currently 92 (natural elements) elements occurring in nature (gold: compounds - substance consisting of two or more different elements co reactions. oxygen etc. ) ratio. Sodium is a metal and pure chlorine is a poisonous gas when che they form and edible compound. The elements of life: 20-25% of the natural elements are essential elements (an organism needs to live a healthy life & reproduce. Iron (needed by all forms of life) - others required for only some species. For vertebrae"s iodine is essential: some naturally occurring elements are toxic to organisms example : Arsenic can be lethal and is linked to numerous diseases.