1 / 8

Topic 1 Introduction to the Study of Life

Topic 1 Introduction to the Study of Life. 1.3 The History of Life Biology 1001 September 14, 2005. Major Events in the History of Life on Earth. The earth formed ~ 4.6 BYA Life probably originated soon after the Earth’s crust cooled, ~ 3.9 BYA The oldest known fossils date to ~ 3.5 BYA

yaron
Download Presentation

Topic 1 Introduction to the Study of Life

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Topic 1Introduction to the Study of Life 1.3 The History of Life Biology 1001 September 14, 2005

  2. Major Events in the History of Life on Earth • The earth formed ~ 4.6 BYA • Life probably originated soon after the Earth’s crust cooled, ~ 3.9 BYA • The oldest known fossils date to ~ 3.5 BYA • Fossils of stromatolites, or layers of bacteria and sediment • The first organisms were the prokaryotes • archaea and bacteria • Autotrophs and then heterotrophs • Dominated the Earth until about 2 BYA

  3. Figure 26.10 Clock analogy for some key events in Earth’s history

  4. Stromatolites Fossilized filamentous prokaryote found in stromatolite, ~ 3.5 BYA, western Australia

  5. Major Events in the History of Life Photosynthesis and Oxygen • Photosynthesis early in prokaryote history did not split water to liberate oxygen • Oxygenic photosynthesis probably evolved ~ 3.5 BYA in the Cyanobacteria • Oxygen began to accumulate in the atmosphere ~ 2.7 BYA • Levels increased dramatically after 2.2 BYA • This “oxygen” revolution posed a challenge to life • Reactive oxygen doomed certain prokaryote groups, forced others into anaerobic environments • Drove a series of evolutionary adaptations including cellular respiration

  6. Major Events in the History of LifeThe Origin of Eukaryotes • The dramatic increase in atmospheric O2 may have followed the evolution of eukaryotic cells containing chloroplasts • The oldest fossils known to be eukaryotes are 2.1 BYA • May be as old as 2.7 BYA according to chemical traces in rock • Called protists – a misnomer “first life” • Eukaryotic cells probably arose from symbiosis and genetic exchange between prokaryotes • From these single-celled eukaryotes arose all the modern multicellular organisms (plants, animals, fungi)

  7. Major Events in the History of LifeThe Earliest Multicellular Organisms • Origin ~ 1.5 BYA (Oldest fossils ~ 1.2 BYA) • The first animals originated ~ 700 MYA

  8. Major Events in the History of LifeThe Colonization of Land • Macroscopic life colonized land ~ 500 MYA • Evolutionary adaptations to prevent dehydration • Plants & fungi first; animals later • The new environment drove many evolutionary more evolutionary adaptations • The human lineage arose about 6-7 MYA

More Related