All the three papers by Benton (1995), Erwin (2001), and Barnosky et al. (2011) talked about the impact of mass extinction on the biological history of earth. Benton (1995) talked about how mass extinction drives diversification in the biological community, Erwin (2001) discussed on how species recovery occurs after mass extinction and Barnosky et al. (2011) talked about the possibility of future mass extinction based on the comparison between the present and past extinction data. According to Benton (1995), the massive diversification of life from a single common ancestor is well known throughout the history of life. However, quantitative documentation was missing. Therefore, Benton (1995) did a quantitative analysis on the diversification
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These major extinctions affected both the terrestrial as well as marine organisms. Benton (1995) adopted several standard methods to measure the magnitude of extinctions: simple counting, percent extinctions, total and per family extinction. From the percent extinction measurement, he identified five deadly mass extinctions at Late Ordovician, Late Devonian, Late Permian, Late Triassic, and Late Cretaceous. These five big mass extinctions were mentioned also by Erwin (2001) and Barnosky et al. (2011). Barnosky et al. (2011) measured the big five mass extinctions based on proportional rate (number of species extinct/time) and magnitude (% of extinct species), which are inextricably linked. Therefore, mass extinction happens if earth loses at least 75% of species within a short geological time frame (at least 2 million years). To measure current extinction rate, Barnosky et al. (2011) used E/MSY (extinction/million species/year) matrix, which were applied on the available mammal extinction …show more content…
However, fossil records of the multicellular organisms suggest slow diversification rate at Precambrian, moderate at Paleozoic and high to exponential diversification rate at Mesozoic and Cenozoic. According to Benton (1995), diversification is not a stochastic but continuous process and taxonomic group/clade addition and multiplication plays a major role in diversification along with adaptation to new habitats. Based on the analysis of the Fossil Record 2, Benton (1995) found an exponential diversity increase for terrestrial organisms from Vendian to Recent. The marine organisms follow more or less the same pattern with a more complexity at Cambrian and Ordovician. Therefore, Benton (1995) refuted any possibility of equilibrium global diversity and denied any use of logistic model to predict past diversity patterns. Barnosky et al. (2011) analyzed long term diversity dynamics of species and argued that current extinction rate is declining within clade diversity for the past 5.3 million years. Therefore, extinction rates have a significant effect on the long term diversity of species. They also pointed out that the current population structure, specifically species richness and evenness that we consider normal today is the result of diversity decline due to human induced
These major extinctions affected both the terrestrial as well as marine organisms. Benton (1995) adopted several standard methods to measure the magnitude of extinctions: simple counting, percent extinctions, total and per family extinction. From the percent extinction measurement, he identified five deadly mass extinctions at Late Ordovician, Late Devonian, Late Permian, Late Triassic, and Late Cretaceous. These five big mass extinctions were mentioned also by Erwin (2001) and Barnosky et al. (2011). Barnosky et al. (2011) measured the big five mass extinctions based on proportional rate (number of species extinct/time) and magnitude (% of extinct species), which are inextricably linked. Therefore, mass extinction happens if earth loses at least 75% of species within a short geological time frame (at least 2 million years). To measure current extinction rate, Barnosky et al. (2011) used E/MSY (extinction/million species/year) matrix, which were applied on the available mammal extinction …show more content…
However, fossil records of the multicellular organisms suggest slow diversification rate at Precambrian, moderate at Paleozoic and high to exponential diversification rate at Mesozoic and Cenozoic. According to Benton (1995), diversification is not a stochastic but continuous process and taxonomic group/clade addition and multiplication plays a major role in diversification along with adaptation to new habitats. Based on the analysis of the Fossil Record 2, Benton (1995) found an exponential diversity increase for terrestrial organisms from Vendian to Recent. The marine organisms follow more or less the same pattern with a more complexity at Cambrian and Ordovician. Therefore, Benton (1995) refuted any possibility of equilibrium global diversity and denied any use of logistic model to predict past diversity patterns. Barnosky et al. (2011) analyzed long term diversity dynamics of species and argued that current extinction rate is declining within clade diversity for the past 5.3 million years. Therefore, extinction rates have a significant effect on the long term diversity of species. They also pointed out that the current population structure, specifically species richness and evenness that we consider normal today is the result of diversity decline due to human induced