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THEORIES OF MASS EXTINCTION Defining concepts and theories

THEORIES OF MASS EXTINCTION Defining concepts and theories. Concepts. Extinction All living individuals of a type (species) have died out and do not exist anywhere on earth. Mass extinctions Periods of time when almost all of the life on Earth died out. Why extinctions?

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THEORIES OF MASS EXTINCTION Defining concepts and theories

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  1. THEORIES OF MASS EXTINCTIONDefining concepts and theories

  2. Concepts • Extinction • All living individuals of a type (species) have died out and do not exist anywhere on earth. • Mass extinctions • Periods of time when almost all of the life on Earth died out. • Why extinctions? • Environmental disasters (e.g. meteor/ asteroid impacts, severe volcanism, cosmic radiation (exploding stars, super-lethal diseases ) • Failure to adapt to habitat or environmental changes (e.g. fluctuating ice/ warm ages, global sea level changes, continental drift )

  3. THEORIES OF MASS EXTINCTION • Continental drift • The movement of separate parts of the earth’s crust (continental plates) over a period of time • Alex du Toit, world famous S,African geologist, pioneered this theory in 1937 in his book “Our wandering continents” 1996-2007 EnchantedLearning.com

  4. CLIMATE CHANGE 1. Cooling of the atmosphere • Ice age • The cooling of the earth and the formation of glaciers that covers a part of the earth’s surface for a period of time • Formation of glaciers causes: • Ocean levels to drop (due to water trapped in glaciers, as ice) • Decrease in O2 levels • Increase in salt (mineral) content of ocean • Change in natural environments

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