Earth Systems 3209

1. Earth Systems 3209 Reference: Chapters 6, 8; Appendix A & B Unit: 2Historical Geology

2. Unit 2: Topic 4.2 Life Forms and Geologic Time Focus on . . . • recognizing that the Phanerozoic Eon represents the emergence of the first visible life in rocks. • listing the different life forms and correlating their presence to corresponding geologic times.

3. Fossils Indicate Evolutionary Pathways: Precambrian (4600 – 540 million years ago) • Little direct evidence of fossils, due to lack of hard body parts. Thus 87% of Geologic time contain little fossil evidence. • As the Precambrian came to a close, the fossil record showed multi-cellular organisms which made it possible for the evolution of more complex plants and animals in the Paleozoic era. • Fossil evidence include;-- algae, bacteria, and traces of soft body organisms.

4. Fossils Indicate Evolutionary Pathways: Paleozoic Era (540 – 245 million years ago) • The beginning of the Paleozoic Era is marked by the first appearance of life-forms which had hard body parts. • Abundant fossils in the Paleozoic allowed scientist to construct a detailed time scale for the last 13% of geologic time. • Paleozoic time can be divided as;Early Paleozoic (Cambrian & Ordovician)Middle Paleozoic (Silurian & Devonian) Late Paleozoic (Carboniferous & Permian).

5. Fossils Indicate Evolutionary Pathways: Paleozoic Era (Early) • Cambrian and Ordovician Periods. • Life during this time was restricted to the seas.Consisted of several invertebrate groups. • Invertebrates evolved into vertebrates. • Cambrian - Trilobite evolved. • Ordovician - Brachiopods evolved - First fish (vertebrate) evolved. • Known as the “Age of the Invertebrates”.

6. Fossils Indicate Evolutionary Pathways: Paleozoic Era (Middle) • Silurian and Devonian Periods. • Life in the water moved to the land, first land plants. • Fish evolved to see the first boney fish and sharks. • Lung fish and lobe-finned fish adapt to land environments. It is believed that these organisms evolved into amphibians by the end of the Devonian period. • Abundance of fishes in the Devonian which is known as the “Age of the Fishes”.

7. Fossils Indicate Evolutionary Pathways: Paleozoic Era (Late) • Carboniferous and Permian Periods. • Plant life at the waters edge moved in land and formed forests by the end of the Devonian. • Amphibians abundant on land. • Amphibians evolved into reptiles in the Permian and reptiles are known as the first true land dwellers.

8. Fossils Indicate Evolutionary Pathways: Paleozoic Era (Late) • Hard shelled eggs made this possible. • Time referred to as the “Age of the Amphibians”. • Mass extinctions of approx 95% of all life. Possible explanation involve the formation of the supercontinent Pangaea. Extinction of trilobite is most common example.

9. Fossils Indicate Evolutionary Pathways: Mesozoic Era - “Age of the Reptiles” (245 – 66 million years ago) • Triassic, Jurassic and Cretaceous periods. • Reptiles have shell covered eggs that could be laid on land. This eliminated the water stage of reproduction as seen with amphibians. This one evolution break through enabled reptiles to dominate Earth for the next 160 million years until the end of the Mesozoic, 66 million years ago. • First flowering plants evolved at the end of the Jurassic period.

10. Fossils Indicate Evolutionary Pathways: Mesozoic Era - “Age of the Reptiles” (245 – 66 million years ago) • One form of reptile made a remarkable step in evolution, it was the first to take to the sky and fly. Jurassic time marked the first evidence of birds in the fossil record. • On land the dinosaur became dominant and this era is called the “age of reptiles – dinosaur.” • First mammals appear. • The end of the Mesozoic Era was marked by mass extinctions of reptiles including dinosaurs and numerous other species.

11. Fossils Indicate Evolutionary Pathways: Cenozoic Era - “Age of the Mammals”.(66 million years ago) • Tertiary and Quaternary periods. • Mammals replaced the reptiles as the dominant animals on Earth. • Flowering plants are the dominant land plant. • Some mammals became extinct during the late Cenozoic (11,000 years ago). These include the mastodon, mammoth, saber-tooth cat, large ground sloth, giant bison and others. • This era is called the “Age of Mammals.”

12. Fossils Indicate Evolutionary Pathways: Single celled -- Invertebrates – Fish -- First land plants -- Amphibians – Reptiles -- Birds -- Flowering Plants -- Mammals

13. Example 1: Which describes the progression of life forms from Precambrian to Cenozoic? (A) amphibians -- fish -- mammals -- reptiles (B) amphibians – mammals – fish -- reptiles (C) fish – amphibians -- reptiles -- mammals (D) Fish – reptiles -- amphibians – mammals In what geological era would one find a rock layer containing numerous dinosaur fossils? (A) Cenozoic (B) Mesozoic (C) Paleozoic (D) Phanerzoic

14. Example 2: What life form was last to evolve? Amphibians (B) fish (C) Mammals (D) reptiles In which era did the organism below exist? (A) Cenozoic (B) Mesozoic (C) Paleozoic (D) Precambrian NOTE: This concept usually tested as multiple choice

15. Your Turn . . . Take the time and complete the following questions . . .(Solutions to follow) Questions: Which geological time span is referred to as the “Age of Reptiles”? Cenozoic(B)Mesozoic (C)Paleozoic (D)Proterozoic Rocks from which era would contain fossils of trilobites? Cenozoic (B)Mesozoic (C)Paleozoic (D)Phanerozoic

16. Solutions . . . Questions: Which geological time span is referred to as the “Age of Reptiles”? Cenozoic(B)Mesozoic (C)Paleozoic (D)Proterozoic Rocks from which Era would contain fossils of trilobites? Cenozoic (B)Mesozoic (C)Paleozoic(D)Phanerozoic

17. Summary . . . Overview of Points covered:

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