Download Final Lecture Notes from 2002

Honors
228
Honors Diagram
Earth Processes
and Evolution
Honors
228
Earth Sciences
Energy and
Natural Resources
Chemistry
Honors
227
Physics
Astrobiology
Biology
Honors
228
Honors
228
Environmental
Sciences
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.
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).
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.
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)
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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)
Universality of Chemistry and
Physics?
• Laws of physics are universal?
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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?
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What do we mean by universal?
What do we mean by Laws of chemistry?
How do we know they operate in the universe?
Conclusion
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?
Historical Debate on Life in
Other Worlds: Speculation
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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
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 (?)
Astrobiology: The Nature of Life
(Chapter 3)
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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)
Properties of Living Systems
• Not laws
• From Bennett et al.:
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Order (hierarchy)
Reproduction
Growth and development
Energy use
Response to the environment (open systems)
Evolution and adaptation
Properties of Living Systems
• From Taylor:
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Hierarchical organization and emergent properties
Regulatory capacity leading to homeostasis
Diversity and similarity
Medium for life: water (H2O) as a solvent
Information Processing
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
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Molecular biology: gene regulation
Biochemistry: enzymes
Organisms: temperature
Globe: “Parable of the Daiseyworld”
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
Molecular Features of Living
Systems
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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
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
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Maintaining function
Feedback Processes
Changing environment
Homeostasis
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
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Prokaryotes and oxygen
Eukaryotes and explosion of diversity
Mass extinctions, asteroids and climate change
Evolutions of humans (what a bore!)
Conclusions
Searching for the Origin
Domain
Bacteria
Domain
Archaea
Common
Ancestor
Domain
Eukarya
Beginnings of Life on Earth
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Organic chemistry*
Transition from chemistry to biology
Panspermia
The evolution of sophisticated features of
metabolism and information brokers
• Conclusions
_________
* Enzymes first
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
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Proteins (relate to information brokers)
Change rate of reactions
High degree of specificity
Regenerated (not consumed)
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)
Urey-Miller Experiment
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)
Prokaryotes and Oxygen
% of Present
4.8
4
3
2
1
0.7
Billions of Years Before Present
0.1 0
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
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
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
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
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
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
Water and Its Properties: Polarity
• Composition and structure: a polar molecule
H+
O
-
H+
• 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
Habitability: Principle and
Application to Astrobiology
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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
Habitability: Introduction
• Define “habitability”
– Anthropocentric perspective
– Astrobiological perspective (capable of harboring liquid
water)
• Key physical and chemical features of habitability
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Surface habitability
Temperature
Source of energy
Liquid water (present and past)
Biological macromolecules (e.g., sugars, nucleotides)
Atmosphere and magnetosphere
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
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)
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
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
Habitability Zone Elsewhere in
the Universe
Progression of the Sciences Leading to Astrobiology
Habitability of
Extraterrestrial
Systems
Copernican
Revolution
Astrobiology
Sun-Centered
World
Revolutions in Physics,
Chemistry,
Geochemistry, and Life
Sciences
Earth-Centered
World