Extinction- What is it ?

Species of animals and plants die out naturally for a number of reasons; such as, disease, climate change and habitat loss. An increase in the diversity of groups, called speciation, results from a modification and adaptation of a existing species/group to create new members; for example, long necks of the group sauropodomorpha (e.g., Dipladocidae) developed to take advantage of food sources higher up trees.


The rate of diversification is a good indication of ecological and biological stresses put upon a group. The inability of a group to cope with stressful circumstances by; speciation, adaptation or endurance, will result in extinction.

Figure 3: Shows the location dinosaurs fossils leading up to the K-T boundaty


It is widely accepted that all geological time periods have a continous level of extinction, known as background extinction. This means that a certain number of species are expected to die out, the average species life expectancy is approximately 4 million years or 20 Ma at the generic level (Sepkoski). Dodson estimated that dinosaur genera lived for 4-8 ma. Overall, dinosaurs were alive on this Earth for approximately 150 million years, which proves they were not a fragile or venerable by any means.


To determine the cause a
mass extinction event (MEE), it is essential to understand; the duration (how long were high levels of extinction's in progress ?), the magnitude (how many species suffered and to what extent?) and the breadth (what species/niches were affected?) of the event in question, Jablonski (1986a).
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