Concept:The Earth's outer structure is made up of the atmosphere, biosphere, and hydrosphere, while the mesosphere belongs to the internal structure.
Explanation:The outer structure refers to the layers that surround the solid Earth and support life and water.
The atmosphere is the gaseous layer around the Earth.
The biosphere is the region where living organisms exist.
The hydrosphere consists of all water bodies on Earth.
The mesosphere, also known as the mantle, is found beneath the crust and surrounds the core.
Hence, the mesosphere is not part of the outer structure.
Answer:Mesosphere.