Читать книгу Oceans For Dummies - Joseph Kraynak - Страница 45

Although scientists may not be able to pin down where all the ocean water came from, one thing we do know for sure is that life on Earth started in the ocean. In fact, it started not too long after the ocean was formed and has continued evolving ever since. Although the ocean probably existed for at least a few hundred million years before signs of life appeared, that’s not very long from a geological perspective. Because life has existed in the ocean for most of the time that the ocean itself has been around, most of the ocean’s history is commonly presented as a timeline designating key stages in Earth’s geological progression coupled with the corresponding evolution of life. Kind of convenient, isn’t it? In this section, we trace the fascinating progression of that evolution, but first, we need to define a few key terms:

 Life is the condition that distinguishes plants and animals (organic) from inorganic matter, such as rocks, minerals, metals, and other substances not derived from living organisms.

 Evolution is the process by which species of organisms arise from earlier life-forms and change over time through natural selection.

 Natural selection is the process by which organisms better adapted to their environment tend to survive and produce more offspring, while those less adapted tend to die out.