Natural and human disturbances constantly change the ecosystems. During this process, older inhabitants die out and new organisms take the action, which causes further changes in the ecosystem. These changes are called ecological succession.
| Primary succession | Secondary succession |
| This is a form of ecological succession, which occurs on soil free surfaces. | This is a form of ecological succession, which occurs after the destruction of primary succession. |
| This succession occurs on surfaces formed due to volcanic eruptions. | This succession occurs after natural destruction or by human activities. For example: regrowth of trees on woodlands after wildfire. |
| Newly exposed surfaces are colonized by various organisms. | Preexisting surfaces are colonized by new organisms. |