Which are statements that are true about ecosystems?

1.The health of an ecosystem is sometimes improved by human activities.
2. Your backyard is an ecosystem.
3. The sun is the primary source of energy in an ecosystem.
4. Hunters have a part in balancing the earth's ecosystems.
5. In a healthy ecosystem, the removal of one organism will have little effect on the rest of the ecosystem.
6. Producers return nutrients to the soil.