Charles Darwin originally published the idea that all species have descended over time from common ancestors. This idea is known as evolution. Which of the following statements best categorized evolution? A
A scientific hypothesis that has not been researched.

B
An unproven observation about a small number of organisms.

C
A scientific fact that has not been modified since Darwin's time.

D
A scientific theory on change of over time that is supported by evidence.

The images show two species of tree frogs in a particular region. the gray tree frogs are adapted to the trees of the woodlands, while the green tree frogs can survive in woodlands or grasslands. the gray frog was abundant in the woodlands. because of climatic changes, most of the trees in the region died, and the woodlands changed to grasslands. in such a case, the . the gray tree frog is closely related to the green tree frog genetically, but they have different mating calls. this suggests that speciation occurred because of .