BIO 234—Fundamental Evolutionary Biology Scottsdale Community College and 2 + 2 partnership with Northern Arizona University Lecture 5.2 Origin of Life Dr. John D. Nagy
Figure 1: Image from NASA’s rover Curiosity on Mars. View is a basin at the base of Mt. Sharp that may have held water in the past.
Summary and Instructions
Complete this lecture by performing the following exercises: 1. Study §11.1 through 11.4 (pages 401–420). 2. Optional: Explore the National Academy of Science’s publication, “The limits of organic life in planetary systems,” (free download) to gain perspective on how professionals deal with defining life (Commitee on the Limits of Organic Life in Planetary Systems et al., 2007). 3. Master the definitions of terms in the vocabulary list below. 4. Answer the focus questions written below; you may submit your answers either through Canvas or via email as a pdf or jpeg.
Nagy, 2021 1 Evol Lec 5.2 Origin of Life Vocabulary
LUCA Prebiotic soup Molecular mutualism Enzyme Protocell Abiogenesis Hypercycles Ribozyme
Focus Questions
Answer the following questions in Canvas. Alternatively, you can answer them in your own media (for example, paper, OneNote, or Word) and submit them through Canvas via email. Please note: If you choose to submit via email, please submit a pdf or jpeg copy of your work. Use your own words and be thorough in all your free-response answers.
Concepts 1. Explain in detail how one can establish that objects like those shown in Figure 11.1 on page 402 of the text are, in fact, microfossils. What else could they be, and how do we determine that they are not those things but actual fossils?
2. Explain why the LUCA is not necessarily the first living thing on Earth.
3. Describe Oparin and Haldane’s “warm little pond” hypothesis explaining how life arose.
4. Explain how Oparin and Haldane’s prebiotic soup hypothesis was tested experimentally by Miller and Urey. Include both a description of the experimental setup and the results, including those obtained by Miller’s later student, Jeffrey Bada.
5. Propose at least 1 alternative hypothesis to the Oparin-Haldane-Miller-Urey prebiotic soup hypothesis on the origin of organic molecules out of which life is built.
6. Critique the Miller-Urey results.
(a) What might have been wrong in their experimental design? (b) What critical events in the origin of life on Earth does the experiment fail to explain? (c) Are these critiques devastating to the Oparin-Haldane hypothesis, or can they be overcome?
7. Explain why natural selection might favor mutualistic hypercycles—like those hypothe- sized by Eigen and Schuster—enclosed in membranes over those not so enclosed.
8. Compare and contrast enzymes and ribozymes.
9. Describe the “RNA-world” hypothesized by Walter Gilbert, and outline the evidence in favor of this hypothesis.
10. Answer Key Concept Question 11.5 on page 419 of the textbook: Compare (and contrast) the Spiegelman and Sumper experiments. Why was Sumper’s acridine orange experiment a stronger test of the power of natural selection to act on RNA-based life?
Nagy, 2021 2 Evol Lec 5.2 Origin of Life Synthesis 1. Suppose machines become intelligent, as in movies and books like The Terminator series, Battlestar Galactica, The Matrix, or I, Robot (the actual book, not the Will Smith movie). The machines begin to manufacture themselves and make perfect, exact copies of each other with only slight, random variations in their construction. They can move, think, and solve complex problems that they have never faced before. They can obtain their own fuel, repair themselves and interact with their environment in complex ways. In particular, they can maintain operations in environmental conditions from the high arctic to the searing desert to the bottom of the ocean to the top of Mt. Everest. Would you consider such machines to be alive? Explain your reasoning. This is a very deep question. Explore it carefully. Use information from the text and the NAS publication mentioned at the start of this lecture if you wish (Commitee on the Limits of Organic Life in Planetary Systems et al., 2007). This should be the longest essay you’ve written in this class so far.
2. Answer Key Concept Question 11.4 on page 417 of the textbook: Was LUCA likely an RNA-based or DNA-based organism? Why?
Image Credits
Figure1, page1: Jet Propulsion Laboratory (NASA) Photojournal page, PIA19839: Strata at Base of Mount Sharp.
References
Commitee on the Limits of Organic Life in Planetary Systems, Space Studies Board, and Board on Life Sciences (2007). The Limits of Organic Life in Planetary Systems. Washington, D.C.: National Academies Press.
Nagy, 2021 3 Evol Lec 5.2 Origin of Life