Methane-producing bacteria grow only under anaerobic conditions. They convert CO2 and H2 into methane. The methane-producing bacteria differ in some of the fundamental biochemical processes of metabolism. Photosynthetic bacteria like plants and algae use pigments to capture light and transform it into chemical energy. The increase in oxygen led to the formation of a layer of ozone, which afforded protection from the sun's ultraviolet radiation.
Most organisms now living are descendants of a few lines of early bacteria.
The Appearance of Eukaryotic Cells 1. Eukaryotic cells first appeared about 1.5 billion years ago. These early cells appear to contain smaller membrane-bound structures like a nucleus. A. Conditions Affecting Origin of Life on Earth 1. The evolution of carbon-based life forms is possible only within a narrow range of temperatures.