Biology Reference
In-Depth Information
teenth century. Especially controversial, vis-à-vis some readings of biblical
scripture, were the implications, fi rst, that immense amounts of time must
be involved, based on observations of processes currently taking place on
Earth (erosion of deep canyons, imperceptible accumulation of sediments)
that in geologic sections measure tens of thousands of feet in thickness; and
second, that the sequence of life generally has proceeded from simple and
few to more complex and diverse. Early on, Smith's views were discredited,
he was mostly excluded from the religious-dominated academic commu-
nity of eighteenth- and nineteenth-century Europe, and he actually spent
time in debtor's prison. The eventual acceptance of the superposition of
strata based on uniformitarian principles was a new paradigm, comparable
in importance to the later recognition of catastrophes and plate tectonics in
revolutionizing the geological sciences, and it facilitated one of the concep-
tual breakthroughs in the thinking of Charles Darwin on evolution.
Biostratigraphy
If the sequence of reversals in the Earth's magnetic fi eld preserved in ocean
basins can confi dently be read from old to young based on the principals
of stratigraphy, then the history of marine life preserved in those rocks
can be read in the same way and correlated with the terrestrial life dur-
ing, for example, the North American Land Mammal Ages, or NALMAs
(fi g. 3.8). As noted, one manifestation of this reading is that life has pro-
ceeded in general from morphological, anatomical, cytological, and bio-
chemical simplicity toward greater complexity. Also, there has been a net in-
crease in biodiversity, albeit episodically (chap. 5), from comparatively few
kinds or species of organisms in older strata, to different kinds and greater
numbers of species in younger strata. This understanding ushered in a new
way of comparing discontinuous strata in widely separated parts of the Earth
through their fossil content (correlation), and detecting small differences
within strata (zonation). Such studies constitute the fi eld of biostratigraphy,
and it is based on the vast array of fossils preserved worldwide throughout
the geologic column in sediments representing a variety of environments.
The fossils include diatoms and other algae; foraminifera, radiolarians, and
allied protozoans; corals, mollusks, gastropods, crinoids, and ammonites
from the marine realm; pollen grains, spores, seeds, fruits, leaves, wood,
phytoliths, and starch grains of plants from ancient bog, lake, swamp, delta,
ocean, and volcanic ash deposits; birds, bats, rodents, insects, fungi, bac-
teria and other plant and animal fossils preserved in sediments including
amber and stalactites; aquatic mammals and vertebrates from whales to
Search WWH ::




Custom Search