BIOL 102 Lecture Notes - Lecture 10: Natural Selection, Body Plan, Cambrian Explosion
14 Feb 2017
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Document Summary
Consequences of continental drift of speciation and biogeography. Formation of the supercontinent pangaea (the latest supercontinent) about 250 million years ago had many effects: a deepening of ocean basins, a reduction in shallow water habitat, a colder and drier climate inland. Continental drift has many effects on living organisms: a continent"s climate can change as it moves north or south, separation of land masses can lead to allopatric speciation. The fossil record shows that most species that have ever lived are now extinct (assumption, rarity of fossils) Extinction can be caused by changes to a species environment. At times, the rate of extinction has increased dramatically and caused a mass extinction. Mass extinction is the result of disruptive global environmental changes. In each of the five mass extinction events, 50% or more of marine species became extinct (estimated b the fossil record) The cretaceous mass extinction occurred 65. 5 million years ago.
