Here's how it's often used:
* Troposphere: The lowest layer of Earth's atmosphere, where weather occurs. The name reflects the constant mixing and changes in this layer.
* Tropopause: The boundary between the troposphere and the stratosphere.
* Tropocollagen: A protein molecule that is the basic building block of collagen, which is a structural protein found in connective tissues. The name refers to its tendency to change shape.
* Tropic: A region near the equator that is characterized by warm temperatures and high rainfall. The name reflects the "turning" of the sun in the sky throughout the year.
So, in general, "tropo" often implies change, turning, or movement.