Chapter 21 Outline

Chapter 21 Outline - Chapter 21 Outline 1) Precambrain Era:...

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Chapter 21 Outline 1) Precambrain Era: longest, earliest (4.5 bya-600 mya) a) Precambrian (not divided into periods) i) Mostly microscopic prokaryotes living in oceans ii) Approximately 2/3 of way through this era, evolved iii) Late Precambrian—many , animals had evolved. iv) Oxygen begins to appear in the atmosphere as a product; well below current levels 2) Palezoic Era: (542-297 mya) a) Cambrian: 542-488 mya i) Beginning of ii) Concentration of O 2 was…? iii) Continents… iv) Largest land mass was called . v) Cambrian explosion:
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b) : 488-444 mya i) Great radiation of… ii) At the end of the period, formed over . iii) Due to the glaciers, sea levels , causing… c) i) ii) First plants appeared late during this period iii) The first also appeared. d) Devonian: i) The northern landmass and the southern landmass moved each other. ii) iii)
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iv) began to occupy land. v) , , and became common in habitats. vi) An extinction of about
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This note was uploaded on 05/07/2008 for the course BIO 1306 taught by Professor Adair,tamarah during the Spring '08 term at Baylor.

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Chapter 21 Outline - Chapter 21 Outline 1) Precambrain Era:...

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