The biosphere consists of all living and non-living things on Earth from bacteria to trees to whales. It extends 8 km above and 11 km below the surfaces of the Earth and ocean. An ecosystem is the basic natural unit of the biosphere and contains both biotic (living) and abiotic (non-living) factors that interact. There are different types of ecosystems including terrestrial, forest, pond, marine, desert, and river. Six levels of biological organization are recognized from the broadest (biosphere) to the most specific (species).