18. the diagram below represents a typical energy
pyramid.
which level in the pyramid includes autotrophs?
a. a
b. b
c. c
d. d

Cells tend to have a relatively small and uniform size. why aren’t cells larger?

Environmental differences within ecosystems are generally caused by

During the winter, this species of fox has white fur, but in the summer, it has brown fur. what environmental change may have lead to this fox's fur color? snow cover increase in sun's brightness volcanic eruption global warming