intensity during the Phanerozoic. As changes
in biodiversity reflect both changes in origination
and extinction, some events shown here are masked
in the biodiversity curve by very rapid replacement
with new species.
(21KB, MIME type: image/png) GNU
Directly from wiki: Following Rohde & Muller
(2005), this figure shows the apparent changes in
marine biodiversity throughout the last 542 million
years (the Phanerozoic eon) based on the first and
last appearance of the 36380 genera recorded in the
Sepkoski Compendium (2002). The "Big Five"
mass extinctions of Raup and Sepkoski (1982) are labeled
as well as a number of additional, but less well-known
extinction events. Conventional symbols for the periods
of geologic time appear along the bottom. The distinctions
for "all genera" and "well-resolved
genera" follow Rohde & Muller (2005) and
reflect either the inclusion of all of Sepkoski's
taxa or only those where the first and last appearances
were well-defined in time.
It is presently a matter of scientific debate whether
the long-term trend appearing here is a genuine reflection
of biological changes or is instead a reflection of
the biases inherent to the process of paleontological
investigation. Some have argued that most, or all,
of the large rise going into the modern day is merely
a reflection of the greater availability and preservation
of recent geologic sections. Others dispute this,
and argue that most of the long-term changes reflect
genuine biological processes.
Rohde & Muller also argue that the fluctuations
in biodiversity, especially occurring in the early
part of the record, are too regularly spaced to have
occurred by random chance. The conclude on the basis
of a statistical argument that some unknown process
influenced the waxing and waning of life with roughly
a 62 million year periodicity. Periodic astronomical
and geophysical processes are considered, but no particular
process is definitively implicated.
Raup, D. & Sepkoski, J. (1982). "Mass extinctions
in the marine fossil record". Science 215: 1501–1503.
Rohde, R.A. & Muller, R.A. (2005). "Cycles
in fossil diversity". Nature 434: 209-210.
Sepkoski, J. (2002) A Compendium of Fossil Marine
Animal Genera (eds. Jablonski, D. & Foote, M.)
Bull. Am. Paleontol. no. 363 (Paleontological Research
Institution, Ithaca, NY).
Then add: Phanerozoic