Nonnative species disrupt ecosystems by
a. increasing biodiversity
b. preventing the spread of disease
c. disrupting food chains
d. increasing the populations of nativespecies

Paleontologists have found plant fossils deep within the layers of the north polar region. these leaf fossils have been labeled as to the rock layers they were found in, with the lower numbers being layers close to the earth's surface and higher numbers representing deeper layers. according to the numbers of these four leaf fossils, what might you infer?