Summary:
- Many individual organisms can be organized into the following levels: cells, tissues, organs, and organs systems.
- An ecosystem consists of all the populations in a given area, together with the nonliving environment.
- The biosphere is the part of Earth where all life exists, including all the land, water, and air where living things can be found.
- A measure of Earth’s biodiversity is the number of different species of organisms that live on Earth.
- At least 10 million different species live on the Earth today.