Life on earth has suffered occasional mass extinctions at least since 542 million years ago. Although they are disasters at the time, mass extinctions have sometimes accelerated the evolution of life on earth. When dominance of particular ecological niches passes from one group of organisms to another, it is rarely because the new dominant group is "superior" to the old and usually because an extinction event eliminates the old dominant group and makes way for the new one.
The fossil record appears to show that the rate of extinction is slowing down, with both the gaps between mass extinctions becoming longer and the average and background rates of extinction decreasing. However, it is not certain if the actual rate of extinction has altered, since both of these observations could be explained in several ways.
ABOUT THE AUTHOR P R Yadav
Dr. P.R. Yadav did post-graduation from Gorakhpur University, Gorakhpur in 1983 and Ph. D. from Banaras Hindu University in 1988. From 12-11-1990 to 31-08-1996 worked as a scientist at the Silkworm Seed Technology Laboratory, Central Silk Board, Bangalore, During this period visited People Republic of China and did a specialized course on Silkworm Nutrition and Physiology from Zhejiang Agricultural University, Hangzhou, China. Resigned the above post and joined as Lecturer in Department of Zoology, D.A.V. College, Muzaffarnagar conseqwuent upon selection by the U.P. Higher Education Services Commission, Allahabad. Has 20 yars research experience and published numerous research papers in journals of international repute. Editing two journals i.e., journal of Experimental Zoology India and Biochemical and Cellular Archives. Has teaching experience at both the graduate and post graduate level. He Prehistoric Animals, Vanishing Animals, Histology, Entomology.
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