This tutorial introduces photosynthesis

Other sections include animal systems, cells, vertebrates, and invertebrates.

Photosynthesis Tests & Worksheets - All Grades

As with enzymes, the molecules used in biological processes are often huge and complex, but ATP energy drives all processes and that energy came from either potential chemical energy in Earth’s interior or sunlight, but even chemosynthetic organisms rely on sunlight to provide their energy. The Sun thus powers all life on Earth. The cycles that capture energy (photosynthesis or chemosynthesis) or produce it (fermentation or respiration) generally have many steps in them, and some cycles can run backwards, such as the . Below is a diagram of the citric acid (Krebs) cycle. (Source: Wikimedia Commons)

Glossary of Terms: P - Physical Geography

The primary heat dynamic on Earth’s surface is that the oceans near the equator are heated by sunlight and spreads the heat toward the poles via oceanic currents. Today’s continental configuration, with three major oceans besides the polar ones, has seen a develop that takes water 1,600 years to travel. Where the Atlantic Ocean meets the polar oceans, which is how the oceans are oxygenated. Without that oxygenation, there would be little life on the ocean floor or much below the surface; almost the entire global ocean would be lifeless. Before the , this was certainly the case, but make the case that the oceans were anoxic for more than a billion years after the GOE began, largely because of the continental configurations and geophysical and geochemical processes.

Above all else, life is an energy acquisition process. All life exploits the potential energy in various atomic and molecular arrangements, or captures energy directly, as in photosynthesis. Early life exploited the . The chemosynthetic ideal is capturing chemicals fresh to new environments that have yet to react with other chemicals. The currently most-accepted hypothesis has life first appearing on Earth about 3.5-3.8 bya, probably in volcanic vents on the ocean floor. The earliest life forms took advantage of fresh chemicals introduced to the oceans. Life had to be opportunistic and quick in order to capture that energy before other molecules did.