Extinction, mass

Ordovician 500 Myr Diversification of echinoderms, other invertebrate phyla, jawless fishes. Mass extinction at end of period (ca. 85To of all species disappear)... 

Quaternary 3 Myr Repeated glaciations. North and South America join mass extinctions of large mammals, evolution of Homo rise of civilizations, humans begin to modify biogeochemical cycles... 

The movement of Earth s crustal plates and the continents they contain - continental drift -has had enormous effects on climate, sea levels, and the distributions of organisms. Mass extinctions of organisms have usually accompanied major drops in sea levels. The collision of all the continents to form the gigantic landmass called Pangaea about 260 million years ago, triggered massive volcanic eruptions. The volcanoes... 

Stanley, S. M. 1986. Anatomy of a regional mass extinction PUo-Pleistocene decimation of the western Atlantic bivalve fauna. Palaios 1 17-36. 

Keller, G. (1986) Stepwise mass extinction and impact events Late Eocene to early Oligocene. Marine Micropaleontology, 10, 267-293. 

Wignall PB, Twitchett RJ (1996) Oceanic anoxia and the end Permian mass extinction. Science 272 1155-1158... 

The unique chemical composition of cosmogenous debris has provided some insight into why approximately 70% of the species of organisms on Earth were driven extinct over a relatively short time interval approximately 66 million years ago. Evidence for this mass extinction has been observed in marine sediments throughout all the ocean basins. In a contemporaneous layer deposited at the end of the Cretaceous period, the hard parts of many species of marine plankton abruptly vanished from the sedimentary record. This sedimentary layer is also characterized by a large enrichment in the rare element iridium. 

Section 8.6.2, the Permian period ended with the largest mass extinction event that has yet occurred on planet Earth. As the ocean began a sustained recovery at the beginning of the Mesozoic era, opportunities likely abounded for the survivors to take over empty ecological niches through evolutionary adaptation. Prior to the advent of planktonic... 

Many of these were lost in a series of mass extinctions long ago we continue to compromise our biodiversity today. 

See S. M. Stanley, Extinction, Scientific American Library, Freeman, New York, 1987. This short book provides a useful and informed discussion of the history of mass extinctions of living species. 

One implication of Earth - degassing models of metallogenesis is that there should be links between the formation of the Earth s resources, secular changes in architecture and geochemistry of the planet over some 4.5 billion years of evolution and phenomena such as mass extinction events, global anoxia, and atmospheric evolution. 

First appearance of the indicated organisms —Mass extinctions (the anew length Is proportional to the extent)... 

Figure 2.I. First appearance of organisms in the perspective of mass extinctions and sea vs...

Figure 7.1.1 Sea vs land occupancy in the perspective of the first appearance of organisms and mass extinctions...

If biodiversity decreases, natural product diversity also decreases, because of a link between the two (Part II). Modem times have seen the greatest natural product diversity. With the increase in plant species from 100,000 before the end-Cretaceous mass extinction to the 250,000 species of modem age, natural product diversity must also have increased. The estimate depends on how natural product diversity is evaluated, i.e. from the molecular skeletons or the actual metabolites. Metabolites of insects, fungi, and bacteria must be added to the list. The present man-made mass extinction may thus result in a larger numerical impact than any previous mass extinction, even if the loss of natiual product diversity occurs at the same percentage of previous catastrophes. 

Fossil molecules and past natural product diversity Fossil remains as old as 3,000 My have been found of the precursors of modem cyanobacteria. The oldest remains of eukaryotes date to 2,500 My. Thus, together with many other landmark findings, the history of fossil remains is illustrative of the past events, in particular mass extinctions, which are dramatic episodes of biodiversity loss from unusual causes. 

Mass extinctions (the arrow length is proportionai to the eident) —Sea vs. land occupancy during the ages... 

Courtillot. V. Gaudemer, Y. (1996) Effects of mass extinctions on biodiversity. Nature, 381, 146-8. 

X = log(D/Dp), Eg is the mass extinction efficiency for species i, and m3(x) is the volume average refractive index as a function of X. Strict application of Equation (1) requires information on all species. 

The species mass extinction efficiency. Eg, can be theoretically determined from Mie s classical solution to light extinction by a sphere in an infinite medium. Computer routines are available to calculate single particle extinction efficiencies, and, hence. Eg ( ). If the mass distribution of each species is... 

Sulfate Average Mass Extinction Efficiency, ct. Comparison of Statistically Inferred Values... 

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