GSC101 University of Miami Evolutionary Tree of Life Reflective Paper minimum 6 pages of text (double-spaced, 1” margins, 12 pt font). Adding a few figures

GSC101 University of Miami Evolutionary Tree of Life Reflective Paper minimum 6 pages of text (double-spaced, 1” margins, 12 pt font). Adding a few figures is fine, but they don’t count toward 6 page text requirement. Due dates will be firm! Late penalty: 2.5 points per day Papers should describe the current state of knowledge of the subject matter, any important unresolved issues, and your suggestions for research directions that could help solve those issues. Suggested outline: 1. Introductory paragraph 2. Summary of current state of knowledge 3. What are the major unanswered questions? 4. How might one or more of these questions be addressed in future research? What are reasonable hypotheses or targets for further exploration or research? 5. Concluding summary 6. Citations – more than just Wikipedia! (I don’t care in what format.)

Topic choosing

4 main Eons and 3 Eras of Phanerozoic Eon • when and why did Earth’s atmosphere develop its O2 content? • summary of evolution of life through present • K-Pg dinosaur extinction event • “Permo-Triassic” extinction event at Paleozoic/Mesozoic boundary

The Four Main Eons of Earth’s History • Hadean – 4.6 to ~4 billion years ago • Named for Greek god of underworld (unknown) • Archean – ~4 to 2.5 billion years ago • Name from Greek word for beginning/origin (of life) • Evolution of microbial life (some with photosynthesis) • But very little atmospheric O2 • Proterozoic – 2.5 billion to 542 million years ago • Name from Greek words for early animals/life • Rise in atmospheric O2 marked boundary from Archean • Rise of eukaryotes and first animals • Phanerozoic – 542 million year ago to present • Name from Greek words for visible animal/life • Boundary marked by explosion of eukaryotic evolution • Multiple extinction/evolution events

What Were Conditions on Earth at End of Hadean Eon/Beginning of Archean Eon (~4 billion years ago)?• Surface temperatures reached a reasonable balance by the end of the Hadean Eon. • Atmosphere was dominated by CO2 and water vapor – no O2. • Water was plentiful on surface of Earth. • Volcanic processes were very active. • However, plate tectonics was probably not fully developed.

Evolutionary Tree of Life on Earth Prokaryotes – single-cell life without nuclei. There are two types, collectively called microbes: • Archaea • Bacteria • Eukaryotes – cells have nuclei. Includes some single-cell life and all multi-cellular life. • Some genetic analysis indicates that bacteria and eukaryotes may have arisen from archaea.

Cambrian explosion of marine multicellular life (~542-490 Ma)Fossil record shows a profusion of new marine organisms with a variety of body types. • Many were invertebrates with hard external skeletons of calcium carbonate/phosphate. • Early versions of arthropods and molluscs can be recognized. • Included earliest primitive vertebrates – primitive fish

Rise of land plants and animals ~450 million years ago • Evolution of amphibians from fish • Profusion of land plants, including widespread Carboniferous swamps that produced much of the world’s coal • Potentially related to collisions of continents to form Pangaea, and resulting climatic changes

When and why did Earth’s atmosphere develop its O2 content? • Basic summary of evolution of life through present • K-Pg dinosaur extinction event

4 main Eons • Rock and fossil record defines geological time scale • What is life? How do we recognize signs of earliest life? • How did life arise on Earth? • Hydrothermal systems: Photosynthesis vs chemosynthesis