1 / 14

Origins of the Earth

Origins of the Earth. Our solar system formed 4.5 – 5 bya Earth – a coalescence of rocks ~ 4.5 bya After sufficient size, gravity strong enough to hold gases. Origins of Life. Early atmosphere Methane (CH 3 ) Carbon dioxide (CO 2 ) Ammonia (NH 3 ) Hydrogen (H 2 ) Nitrogen (N 2 )

macha
Download Presentation

Origins of the Earth

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. Origins of the Earth • Our solar system formed 4.5 – 5 bya • Earth – a coalescence of rocks ~ 4.5 bya • After sufficient size, gravity strong enough to hold gases

  2. Origins of Life • Early atmosphere • Methane (CH3) • Carbon dioxide (CO2) • Ammonia (NH3) • Hydrogen (H2) • Nitrogen (N2) • Water vapor (H2O) • C, N, H, and O are basic elements of life

  3. Origins of Life • Early Earth inhospitable • Once begin cooling, condensation • Formation of oceans • Set stage for first life – about 3.5 bya

  4. How Can We Look Back Billions of Years • Principle of Continuity – Any stage of life’s evolution should derive from preexisting states. • Signature Principle – Prebiotic processes should be evident in biochemistry of modern life • No-free-lunch Principle – all life requires energy to grow

  5. Hypotheses and Testing • These three principles + essentials of life allow for generation of testable hypotheses on formation of life • Essentials of Life • Described in introductory lecture

  6. Origins of Life • No free oxygen in early atmosphere • But doesn’t all life require oxygen? • Precursors for life – simple molecules (remember hierarchy of life) • Stanley Miller’s Experiments (1950s)

  7. Reaction formed simple molecules Simple molecules formed amino acids, purines, and pyrimidines

  8. Building Blocks of Life • Molecules (amino acids, etc.) are not life • Building blocks would continue to accumulate • Next step would be formation of macromolecules (proteins, polysaccharides, nucleic acids) • Formed by polymerization (repeated condensation of monomers – Chapter 3) • Key is a lot of building blocks needed

  9. Building Blocks of Life • Molecules are not life – prebiotic • For life, three other conditions must be met: • Replicators – self-reproducing molecules • Error via mutation • Energy and partial isolation from environment

  10. Isolation from Environment • Why? • Eliminate interference with chemical reactions • Protobionts • Aggregates of prebiotic molecules that create an isolated internal environment • Produced experimentally in 1920s

  11. Replicator Molecules • RNA was probably first • Experiments in 1970s and 1980s demonstrated that RNA could use simple molecules to build nucleotides and more complex molecules • A replication error could lead to DNA later after living organisms present

  12. First Life • A collection of protobionts • Contain all the essentials of life • Probably a heterotrophic bacteria • Feeding on organic molecules • Anaerobic

  13. We will continue topics on the orgins of prokaryotic and eukaryotic life later as we move through those groups

More Related