The layer where organisms can exist on the surface of the Earth is called the biosphere.

Here's why:

* Biosphere: This encompasses all life on Earth, including all living things, their habitats, and the interactions between them. It extends from the deepest parts of the ocean to the highest mountain peaks.

* Other relevant layers: While the biosphere is the overarching term, it includes parts of other layers like the atmosphere (the air), the hydrosphere (the water), and the geosphere (the Earth's crust and mantle).

Let me know if you'd like to learn more about the biosphere or any of its components!