| Multicellular organisms then appeared and | | |
| Photosynthetic organisms gradually produced the chemically unstable oxygen-rich atmosphere that | | |
| Terrestrial life developed later, after the ozone layer protecting living beings from | | |
| Diversification of terrestrial species is thought to be increased by the continents drifting apart, or | | |
| Biodiversity is expressed at the ecological level (ecosystem), population level (intraspecific diversity), species level (specific diversity), and | | |
| Recently technology has allowed the discovery of | | |
| This remarkable ecological system is not dependent on sunlight but bacteria, utilizing the chemistry of the hot volcanic vents, are at | | |
