Biology Reference
In-Depth Information
through erosion or sedimentation, as we shall see in chapter 9. Together
with the myriad effects of climate change—temperature, precipitation, gla-
ciation, water-table fl uctuations—they create a dynamic system favorable
to the generation of novel genotypes, molecularly distinct entities, and new
phenotypes (morphologically different forms). These novelties are acted
upon by evolutionary processes such as mutation, hybridization, competi-
tion, and extinction to produce new species and account for the biodiversity
of ecosystems. It is ironic that not so many years ago, the lowland neo-
tropical rain forest, the most diverse of all ecosystems, was characterized
as environmentally and biologically stable and unchanging. One of the sig-
nifi cant contributions of geological and biological investigations, including
vegetational history studies, has been to document that tropical ecosystems
have undergone considerable alterations in range, habitat, and environment
throughout Cretaceous and Cenozoic time.
In the Central Andes, a plant fossil of unspecifi ed age, but worthy of
mention, was obtained by W. F. Parks of St. Louis, Missouri, from a curio
shop in Cuzco, Peru. He sent it to F. H. Knowlton (1919), who described
it as
Zea antiqua
, an ear of corn (fi g. 7.7), and it was later cited in papers
dealing with the origin of maize. Among features that might have raised
concern, besides having been purchased in a curio shop, were that it was
made of baked clay, it still bore the marks of the tool used to bore a small
hole into the hollow center, and it contained pellets that rattled when the
object was shaken. It recalls Beringer's predisposition to accept discarded
Figure 7.7
Supposed fossil ear of corn reported from
Cuzco, Peru. From Brown 1934. Used with permission
from the Washington Academy of Sciences, Washing-
ton, DC.
