Читать книгу Oceans For Dummies - Joseph Kraynak - Страница 48

Before moving on to the evolution of more complex organisms, we’d like to give a shout out to energy — the power that sustains life and drives evolution. So where does all this energy come from? It comes from a set of life-sustaining chemical reactions in organisms collectively referred to as metabolism. These chemical reactions can be divided into two types:

 Anabolic processes build molecules. When you’re pumping iron at the gym, anabolic processes are at work synthesizing protein molecules to build muscle. Energy is required to fuel anabolic processes.

 Catabolic processes break down molecules into smaller units, often releasing energy; for example, your body can break down sugar or fat molecules to give you the energy to pump that iron.

All living things use the stuff around them to obtain the energy and molecules they need to carry out vital cellular processes, to reproduce, and, in some cases, to move around. However, every known ecosystem on Earth is fueled by organisms that rely on one of the following two metabolic mechanisms:

 Photosynthesis is the best known of these processes and uses energy from the sun to convert carbon dioxide and water into chemical energy and organic molecules needed for growth. Lucky for us, oxygen is released as a waste product

 Chemosynthesis is less well known and uses energy stored in the chemical bonds of inorganic chemicals such as hydrogen sulfide and methane to make glucose from carbon dioxide and water. Chemosynthesis is what enables bacteria to live near hydrothermal vents at the bottom of the deep blue sea. (See Chapter 5 for more about life that exists around hydrothermal vents.)

Organisms that rely on chemosynthesis and photosynthesis anchor the food webs that enable ecosystems to develop. They’re sort of like the farmers who grow all the food, except they are the food!