Exploring Life's Origins: A Journey Across the Universe

1. Honors Diagram

2. Synopsis This course will study the origin and development of life on the planet Earth within the context of an evolving universe. We review the origins of the universe from the "Big Bang" to our own solar system and integrate the principles of physics, chemistry, geology and biology to study the origins of life on Earth. We address the ultimate fate of life in the universe based upon our understanding of thermodynamics, expansion of the universe, and properties innate to all living systems.

3. Synopsis Continued The essential features of all living systems are discussed as they relate to what we might expect in terms of life elsewhere in the universe. This analysis is based on features of living systems on Earth (plant, animal and microbe), including those from very extreme environments (extremophiles).

4. Synopsis Continued The labs are an integral part of the course and include computer simulations and hands-on experiments to demonstrate essential features of the (i) origins of the universe, (ii) life on the planet Earth, (iii) search for life on Earth and elsewhere in the universe, and (iv) extraterrestrial space travel and exploration.

5. Astrobiology: Week 2 Lecture • Universe of Life? (Chapter 1) • Recapitulate last week • Universality of biology • New science of astrobiology • Life in the Universe: From Speculation to Science (Chapter 2) • History of speculation • Transition to the science • Revolution in the Physical Sciences: Copernicus • Revolution in the Geological Sciences: Wegener • Revolution in the Life Sciences: Darwin, Mendel, Watson and Crick • Nature and Methods of Science (Chapter 2: Geller)

6. Universality of Chemistry and Physics? • Laws of physics are universal? • What do we mean by universal? • What do we mean by Laws of physics? • How do we know they operate in the universe? • Conclusion • Laws of chemistry are universal? • What do we mean by universal? • What do we mean by Laws of chemistry? • How do we know they operate in the universe? • Conclusion

7. Universality of Biology? • Characteristics (laws?) of biological systems universal? • What do we mean by universal? • What do we mean by characteristics of biological systems? • How do we know they operate in the universe? • Conclusion?

8. Historical Debate on Life in Other Worlds: Speculation • Mythology (< 600 BC) • Atomists (~600 BC – 400 BC) • Aristolelians (~400 BC – 300 BC) • Christianity (Middle Ages) • Transition: Speculation to Science • Copernican Revolution • Revolution in the Life Sciences and Geology • Summary: role of science versus speculation

9. Revolution in the Sciences and Question of Life in Universe • The process of change (speculation to science) • Change in human perspective (stars are just not lights but other worlds) • Idea of extraterrestrial life • Universality of Laws of physics • Universality of Laws of chemistry • Dynamic state of Earth’s geology • Rise of the life sciences (from Darwin to bioinformatics) • Universality of characteristics of living systems (?)

10. Astrobiology: The Nature of Life(Chapter 3) • Properties of Living Systems • Evolution as a Unifying Theme • Structural Features of Living Systems • Biochemical and Molecular Features of Living Systems • Instructional Features of Living Systems • Evolution as a Unifying Theme • Extremophiles on Earth and Elsewhere • Define Life (homework assignment and rappateur session)

11. Properties of Living Systems • Not laws • From Bennett et al.: • Order (hierarchy) • Reproduction • Growth and development • Energy use • Response to the environment (open systems) • Evolution and adaptation

12. Properties of Living Systems • From Taylor: • Hierarchical organization and emergent properties • Regulatory capacity leading to homeostasis • Diversity and similarity • Medium for life: water (H2O) as a solvent • Information Processing

13. Properties of Living Systems: Regulatory Capacity • Define “regulatory capacity” • Relate to open systems • Define “homeostasis” • Role of feedbacks (positive and negative) and cybernetics • Why is “regulatory capacity and homeostasis” and important property of living systems? • Examples • Molecular biology: gene regulation • Biochemistry: enzymes • Organisms: temperature • Globe: “Parable of the Daiseyworld”

14. Structural Features of Living Systems (continued) • Evolution of cell types • Prokaryotes • Cell, membranes but no nucleus • Examples: bacteria • Eukaryotes • Cell, membrane, and nucleus • All higher plants and animals • Evolution of cell types • Points to a common ancestor

15. Molecular Features of Living Systems • Genes and genomes • Replication of DNA • Transcription, translation, and the genetic code • Polypeptides and proteins • Biological catalysis: enzymes • Gene regulation and genetic engineering • Points to a common ancestor

16. NASA’s Definition of Life • “System possessing the ability of maintaining form and function through feedback processes in face of a changing environment, resulting in homeostasis” …Chris McKay • Key Points in definition • Maintaining function • Feedback Processes • Changing environment • Homeostasis

17. Origin and Evolution of Life on Earth (Week 5) • Searching for the origin • Functional beginnings of life • Focus on enzymes (lab) • From chemistry to biology at the molecular level • Prokaryotes and oxygen • Eukaryotes and explosion of diversity • Mass extinctions, asteroids and climate change • Evolutions of humans (what a bore!) • Conclusions

18. Searching for the Origin Domain Domain Domain Bacteria Archaea Eukarya Common Ancestor

19. Beginnings of Life on Earth • Organic chemistry* • Transition from chemistry to biology • Panspermia • The evolution of sophisticated features of metabolism and information brokers • Conclusions _________ * Enzymes first

20. Catalysis in Living Systems: Enzymes • Introduction • Most reactions are very, very slow (not sufficient to sustain life) • Mechanisms to accelerate specific reactions: preferential acceleration • Evolutionary significance: positive fitness • Accelerants = Catalysts = Enzymes • Proteins (relate to information brokers) • Change rate of reactions • High degree of specificity • Regenerated (not consumed)

21. Ribozymes • What are ribozymes in current biochemistry? • NOT ribosomes • mRNA (small fragments) • Functions • Synthesis of RNA, membranes, amino acids, ribosomes • Properties • Catalytic behavior (enhance rates ~20 times) • Genetically programmed • Naturally occurring (60-90 bases)

22. Urey-Miller Experiment

23. Functional Beginnings of Life: Transition from Chemistry to Biology • Evolution of Photosynthesis CO2 + H2O + Light = CH2O + O2 • Key processes • Absorption of light (pigments) • Conversion of light energy into chemical energy (ATP) • Synthesis of simple carbon compounds for storage of energy • Purple bacteria and Cyanobacteria • Primitive forms (~3.5 BYA)

24. Prokaryotes and Oxygen % of Present 4.8 4 3 2 1 0.7 0.1 0 Billions of Years Before Present

25. Eukaryotes and an Explosion of Diversity • Incremental changes in evolution: role of oxygen and diversification of organisms (explain ATP fitness) • Quantum changes in evolution • Symbiosis • Lynn Margulis theory: eukaryotes are derived from prokaryotes • Compartmentalization and organelles • Bacterial origins of chloroplast and mitochondria

26. Mass Extinctions, Asteroids and Climate Change • Mass extinctions • Dramatic declines in a variety of species, families and phyla (>25%) • Timing of decline is concurrent • Rate of decline is precipitous (geological sense) • Example of catastrophism • Best example • Cretaceous/Tertiary boundary (65 M years ago) • K-T boundary and Alvarez theory of catastrophism

27. Origin and Evolution of Life on Earth: Conclusions • Plausible scenario for the early origin of life on Earth (abiotic and biotic) • Role of mutation and evolution in origin of increasingly more complex forms of metabolism • Role of major evolutionary and climatological events in “pulses” of diversification in biota

28. Searching for Life in Our Solar System: Chapter 6 • Introduction • Environmental requirements of life • Elements of the periodic table • Energy for metabolism • Liquid solution for living systems • Concept of “habitability zones” • Passing the baton to Professor Geller

29. Energy for Metabolism • Introduction • Sunlight and photochemical energy • Energy decreases with square of distance from source (e.g., Sun) • Example: leaf on Earth versus leaf twice as far out from Earth (1/4 as much energy) • Example: 10 times further out, energy would be 1/102 or 0.01times as much

30. Liquid Solution for Living Systems • Introduction • Life on Earth in water….~4 BYA • First 3 BY of life in water alone • All life tied to watery medium (plants, animals and microbes) • “Habitability” of Earth f [water] • Simplicity and complexity of the nature of the water molecule • Deceptively simple in structure • Exquisite in function

31. Water and Its Properties: Polarity • Composition and structure: a polar molecule • Features • Attraction is electrical • Hydrogen bonding among two molecules of H2O • Exquisite properties of H2O arise from chemical attractions because it is a polar molecule: emergent properties H+ O - H+

32. Habitability: Principle and Application to Astrobiology • Introduction • Concept of “habitability zone” • Comparative habitability of the terrestrial planets • Parable of the Daiseyworld (laboratory) • Factors that underpin habitability • The Sun’s habitability zone • Habitability outside our Solar System

33. Habitability: Introduction • Define “habitability” • Anthropocentric perspective • Astrobiological perspective (capable of harboring liquid water) • Key physical and chemical features of habitability • Surface habitability • Temperature • Source of energy • Liquid water (present and past) • Biological macromolecules (e.g., sugars, nucleotides) • Atmosphere and magnetosphere

34. Concept of a Habitability Zone • Definition of habitability zone (HZ) “Region of our solar system in which temperature allows liquid water to exist (past, present and future)” • Phase diagram for H2O • Retrospective analysis of HZ using the terrestrial planets as case study • Mars, Venus and Earth • Prospective analysis of HZ

35. Comparative Habitability of Terrestrial Planets • Venus (0.7 AU; radius 0.95; same density as Earth) • Very hot; evidence of liquid water in the past • Mars (1.5 AU; radius 0.53) • Very cold; evidence of water today and in the past • Earth (1.0 AU; radius 1.0) • Temperature moderation; liquid water today and in the past • Keys • greenhouse effect (CO2, H2O, oceans) • size of planet (tectonics, gravity, atmosphere) • proximity to Sun (luminosity)

36. Parable of the Daiseyworld: Summary • Basic principles of Daiseyworld model • Cybernetic system • Role of biota in governing temperature when luminosity changes (i.e., increases as in Earth’s evolution; catastrophic change) • Appreciate role of models in scientific method • Hypothesis: atmosphere as a signature of life on a planet • Add biota to your list of factors affecting habitability

37. Continuous Habitability Zone of Our Solar System • Outer edge of HZ must be less than Mars (1.5 AU) orbit (closer to Earth than to Mars) • Estimate of ~1.15 AU • Inner edge of HZ closer to Earth than Venus because Venus lost its greenhouse of H2O early in its evolution • Estimate of ~0.95 AU • Conclusion: for planet to maintain liquid H2O continuously for 4 BY, HZ is as follows: • >0.95 AU < 1.15 AU • HZ of only 0.2 AU in breadth

38. Habitability Zone Elsewhere in the Universe

39. Progression of the Sciences Leading to Astrobiology Habitability of Extraterrestrial Systems Astrobiology Copernican Revolution Sun-Centered World Revolutions in Physics, Chemistry, Geochemistry, and Life Sciences Earth-Centered World