Final answer:
A cline is gradual variation in the geographic distribution of a trait across an ecological gradient, with examples including larger body sizes in polar warm-blooded animals and varying flowering times in plants along mountainsides.
Step-by-step explanation:
Gradual variation in the geographic distribution of a trait is called a cline. A cline is a type of geographic variation observed in populations of a given species that change incrementally across an ecological gradient. An example of this would be endothermic, or warm-blooded animals, which tend to have larger bodies in cooler climates nearer the earth’s poles to better conserve heat. This is known as a latitudinal cline. Conversely, altitudinal clines exhibit adaptations like flowering plants blooming at different times depending upon their elevation on a mountainside.