Download Life on Our Evolving Planet

Life on Our Evolving Planet slide notes
© Bob Field 2007-1212
The entire slide show is on my website at www.calpoly.edu/~rfield. Select the global evolution link and then open the
LifeEvolvingPlanet.ppt and LifeEvolvingPlanet.doc links. A more detailed slide show is at the PGEM database link.
Additional information is available by Googling key words. I am looking for faculty and highly motivated students with
good general problem solving skills to participate in my extremely cross-disciplinary global evolution studies for credit.
1. I retired from a twenty year career as an optical physicist designing and analyzing aerospace laser optical systems. I
spent ten years as an informal science educator in state parks and at the museum of natural history developing
evolution based walks and talks. I spent seven years as an adjunct physics professor supervising student projects and
developing and teaching a solar and global evolution course. I am also a research scholar in residence.
2. The defining property of a system is that it has parts that interact. A closed system does not interact with its
environment – an idealized state that is only approximated by systems smaller than the entire universe. In contrast, an
open system has energy and/or matter flowing into and/or out of it. The second law of thermodynamics states that the
entropy of an isolated system which is not in equilibrium will tend to increase over time; it does not apply to open
systems. The entropy of the Sun or of an organism can decrease over time. For non-specialists of all ages, Dr. Art
Sussman’s Guide to Planet Earth provides an excellent brief introduction to the Earth as a system with energy flows,
matter cycles, and a web of life.
3. My story “Life on Our Evolving Planet” begins as follows: The National Academy of Sciences says that it is the role
of science to provide plausible natural explanations of natural phenomena. The ultimate question for Earth System
History is: How did a giant cloud of cold dilute gas and dust evolve into astronauts in a spacecraft orbiting a planet
orbiting a star?
4. The long answer may take 30 hours to explain. The short answer is: Simple building blocks evolve into complex
systems when energy flows. When the parts of a system interact, some of them may change over time, which is a
broad definition of evolution for any system. Everything Evolves: oceans and atmosphere, solid Earth and Sun,
molecules and cells, organisms and ecosystems.
5. The lightest and most abundant chemical elements in the periodic table are near the top of the chart. Nearly 99.9% of
the mass of the known universe consists of hydrogen and helium, the two elements formed immediately after the Big
Bang 13.7 billion years ago. Within three minutes, the universe expanded and cooled so quickly that no elements
heavier than hydrogen and helium were formed. All other naturally occurring elements were formed by fusing smaller
nuclei inside earlier generations of very hot large stars. Carbon, nitrogen, and oxygen are the next most abundant by
mass, followed by a dozen other common elements shown in the table. Their abundances are minimal but essential to
us. Our Sun fuses hydrogen into helium in its core and generates energy (E=mc 2) which is radiated into the universe
either as waste heat or life giving sunlight depending on your perspective. The Sun has fused hydrogen for over 4.5
billion years and will continue for five billion more years, but it cannot fuse any elements beyond carbon.
6. The composition of the Sun is also at least 98% hydrogen and helium by mass, but it is enriched with so called
“metals” that it inherited from the explosion of a nearby supernova. The Sun has one or two percent “metals”, which
is about ten times that of the material universe. As expected oxygen, carbon, and nitrogen comprise most of the
“metals”. Like the universe, most other elements are rare, but essential to maintain the high core temperature.
7. The volatile component of a comet consists almost entirely of six elements: oxygen, carbon, hydrogen, nitrogen, and
small amounts of sulfur and phosphorus. Light gases like hydrogen and helium escape the minimal gravity of comets.
If we imagine that comets deposited much of our planet’s early reducing atmosphere, we can easily compose a
plausible ancient atmosphere that resembles the comet’s composition by combining two carbon dioxide molecules,
one methane, one ammonia, and four water molecules. Unlike our present oxidizing atmosphere, a prebiotic soup with
amino acids and other organic building blocks can be formed when energy flows through a reducing atmosphere
composed of very few elements.
8. Bacteria and mammals consist of the same six elements (CHONSP) as comet volatiles in similar proportions.
Mammals also concentrate the element calcium, which is somewhat toxic to cells, in bones. Again, most other
elements are rare but essential.
9. Seawater and the dry atmosphere consist mostly of two elements each. Oceans are overwhelmingly oxygen by mass
with some hydrogen, sodium, and chlorine. The atmosphere is mostly nitrogen and oxygen with a little argon. The
atmosphere does not retain much hydrogen in any form other than water vapor, which is no longer very abundant
because it condenses in the moderate temperatures of the current atmosphere, but is constantly recycled between the
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sea and the sky as the sea absorbs energy. The carbon has been depleted from the oceans and atmosphere by being
bound up in carbonate rocks and/or buried in sediments as a result of geochemical and biogeochemical processes.
Four elements comprise over 90% of the solid Earth: iron, oxygen, silicon, and magnesium. These plus five more
comprise 99.5% of the Earth’s mass. Most of the iron and nickel sank to the core early in the Earth’s history. The
lightweight continental crust floats permanently on the surface of the Earth and is dominated by oxygen and silicon
with small amounts of aluminum, iron, calcium, and magnesium. Continents have more silicon and much less
magnesium than the ocean crust or the mantle. Continental crust forms from lighter elements by chemical
differentiation of subducting ocean crust, a process powered by the decay of rare elements like uranium and thorium.
The solar system has an abundance of molecules that are building blocks for the key molecules of life: amino acids,
nuclei acids, phospholipids, and sugars. Six elements are essential to these molecules: carbon, hydrogen, oxygen,
nitrogen, sulfur, and phosphorus (CHONSP). The Earth attracts 100 tons of IDPs (interplanetary dust particles) per
year and collected orders of magnitude more per year earlier in the planet’s history.
Even cell-like fatty membrane spheres of phospholipids form naturally in meteors from carbon monoxide, hydrogen,
and phosphate building blocks.
Modern cells are chemical factories that store, exchange, and transform matter, energy, and information. The
evolution of information bearing molecules that can be replicated and translated into proteins is one of the emergent
properties of matter that distinguishes life from inanimate objects. The historical division of life into plants and
animals can be subdivided into five kingdoms: plants, animals, algae, fungi, and bacteria. Four kingdoms are
members of a domain called eukaryotes which have large cells with true membrane bound nuclei of DNA and
complex organelles like mitochondria and often chloroplasts that were acquired by endosymbiosis. The fifth kingdom,
bacteria, turns out to consist of two distinct domains of prokaryotes, the archea and the eubacteria. All three domains
of modern cells are descended from a common ancestor population that evolved about four billion years ago from
more primitive protocells. All modern cells share many common molecules, structures, and metabolic processes.
The animation dramatizes the concept that photosynthesis combines sunlight, carbon dioxide, and water to make
glucose and the toxic waste product oxygen. We have previously noted that protons, neutrons, and electrons are
building blocks of chemical elements, which are building blocks of simple molecules, which are building blocks of
complex molecules, which are building blocks of simple cells, which are building blocks of unicellular colonies and
of complex cells, which are building blocks of multi-cellular organisms, which are building blocks of ecosystems,
which are building blocks of the biosphere. In all natural systems (ocean, atmosphere, solid Earth, Sun, and biosphere)
there is another set of building blocks which are not materials but processes. Complex multi-step processes like
photosynthesis and aerobic respiration do not appear naturally until simpler processes are combined and/or modified
generally to provide substantial gains in energy efficiency.
The animation dramatizes the concept that aerobic respiration liberates energy by oxidizing glucose into carbon
dioxide and water. One glucose molecule can provide energy for 36 ATP molecules, which are the basic energy
currency of all living cells. Simpler processes like anaerobic fermentation release far less energy because glucose is
not fully oxidized into its original building blocks. Metabolic complexity grows when energy flows. Aerobic
respiration is the engine that powers the complex eukaryote cells and led to the evolution of multicellular organisms.
The animation dramatizes the concept that ribosomes synthesize proteins by translating messenger RNA to transfer
RNA that are attached to amino acids that are combined into polypeptide polymers of protein by dehydration
condensation. While this complex process involves the use of information in nucleic acid sequences, the same
dehydration condensation process is used to polymerize simple sugars into complex carbohydrates and to form
nucleotides from its constituents and then into RNA and DNA polymers.
Organisms interact in an ecosystem such as a tide pool because the meeting of sunlight, water, nutrients, and minerals
provides plenty of resources to feed complex processes. Note that some organisms like the green sea anemone include
a symbiotic relationship between a photosynthesizing organisms and an animal. Also note that red coralline algae use
pigments other than chlorophyll for photosynthesis and produce silica skeletons similar to primitive animals.
This complex flow chart shows interacting Earth systems including the solid Earth, hydrosphere, atmosphere,
biosphere, and non-terrestrial influences (Sun, Moon, dust, comets, and extinction-producing asteroids). The building
blocks of these systems include gravitational, thermal, chemical, electromagnetic, optical, and nuclear processes.
This power density table quantifies the claim that when energy flows, complexity grows. As massive and hot as stars
are, these simple systems of gases have ten thousand times less power per kilogram flowing through them than far
more complex living systems like animals.
20. I am preparing to write a popular science book called “The Facts of Life” which covers everything in this slide show
including the greatest story rarely told: the five billion years of physical, chemical, and biological evolution of the
Earth and its biosphere. Students and faculty are welcome to help.
21. My website has three sections for natural science (mostly cal poly student projects involving math models), natural
history (mostly informal science education programs), and global evolution (which is sketchy so far but includes this
slide show and notes as well as other materials).
22. I am seeking students and faculty to help me develop a global evolution website featuring a five billion year timeline
of globally important events in 100 million year intervals, a database of material properties and processes of the Sun
and the Earth and its subsystems, time dependent math models of solar and global system structures and flows of
energy and material, and constructivist thematic educational resources for middle school to graduate school students
and educators as well as the general public.
23. A traditional geologic time scale (circa 1983) emphasizes the Phanerozoic Era whose rich fossil record followed the
Cambrian explosion of complex multicellular organisms with hard mineral body parts. The scale emphasizes the most
recent four million years, de-emphasizes the first four billion years of Earth history, and ignores the nine billion years
of cosmic evolution that preceded the formation of the Earth.
24. A typical timescale emphasizes the last four million years of hominid evolution culminating in the development of
writing. A popular belief system denies that the universe existed during the 13.7 billion year period before people
began keeping written records of events 6000 years ago.
25. The same timescale summarizes four billion years of pre-Cambrian Earth system history with no more detail than the
most recent four million year period of hominid evolution.
26. My natural history of planet Earth timeline divides five billion years of global evolution into equal 100 million year
intervals and seeks to identify and sequence globally important events and processes whether or not they appear in the
spotty fossil record of ancient history. My emphasis is on connections not collections.
27. I am seeking students and faculty to participate in Senior Projects, Summer Projects, non-thesis Masters Projects, or
Special Problems BIO, GEOL, CHEM, or PHYS 200 or 400. Students may do secondary research, library research
(books, journals, websites), original thinking, and/or data analysis in any one of the following three areas. Five Billion
Years of Global Evolution: Identify and sequence globally important physical, chemical, and/or biological events
and processes in the five billion year history of the solid Earth, hydrosphere, atmosphere, and/or biosphere
(molecules, cells, organisms, and ecosystems) with emphasis on Pre-Cambrian eras. Prokaryote and Eukaryote
Evolution: Study the structure and evolution of prokaryotes, eukaryotes, biologically important molecules, and/or
metabolic processes. Emphasis is on Pre-Cambrian cladograms based on molecular clocks and fossil records.
Biochemical and Geochemical Evolution: Study biochemical, geochemical, and/or biogeochemical properties and
processes from cellular to global scales in Hadean, Archaean, Proterozoic, and/or Phanerozoic Eras.
28. The two cladograms show phylogenetic trees that span four billion years of prokaryote and eukaryote evolution based
on molecular dating methods. There is a variety of projects available. Evaluate accuracy of molecular timescales.
Identify and describe node organisms and characters. Provide common names for each label. Enter data into my 5 BY
timeline. Investigate environmental and ecological causes. Examine environmental and ecological impacts. Describe
ecosystems prevalent in each era. Create separate charts for each geologic era.
29. The water cycle is a familiar and vital example of a geochemical cycle. The cycle provides fresh water for life on
Earth and transfers 20% of the energy absorbed by oceans to the atmosphere without requiring a twenty degree
increase in sea surface temperature to radiate absorbed energy away. The cycle also affects geochemical weathering of
the continents and transports minerals and nutrients from the land to water-based organisms. The persistence of liquid
oceans for four billion years is a result of geochemical and biogeochemical reduction of carbon dioxide greenhouse
gas in the atmosphere that previously served to maintain elevated sea surface temperatures before the Sun’s
luminosity increased 40%.
30. The water cycle is driven by the absorption of solar energy by water. Although pure water appears to be transparent, it
is actually completely opaque to sunlight. Infrared, red, yellow, and ultraviolet wavelengths do not penetrate very far
at all and ultimately even green, blue, and violet wavelengths are absorbed. The absorption of sunlight and long
wavelength infrared radiation (LWIR) from the atmosphere heats the upper portion of the ocean. Some of the sunlight
is utilized by photosynthetic organisms in the photic zone.
31. Sunlight absorbed by the atmosphere and oceans varies sharply with latitude because of the curvature of the Earth’s
surface. Temperature gradients between the tropics and polar latitudes produce density variations which drive thermal
convection. The atmosphere and the oceans remove heat from the tropics and deliver it to higher latitudes, which
moderates climate across the planet and maintains liquid oceans in the Torrid and the Frigid Zones. The circulation of
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the ocean also transports nutrients and influences regional saline concentrations. The ever-changing locations of
continents alter the general circulation of the oceans.
The Troposphere contains 75% of the atmosphere. It is heated from below because the Earth’s land and oceans absorb
sunlight and LWIR and reradiate LWIR to the atmosphere which absorbs the LWIR. Because the atmosphere is so
opaque to LWIR, heat is transported across the Troposphere by thermal convection currents, hence its name “tropo”
which refers to “turning over”. The temperature gradient across the 10 km thick Troposphere is about 130 Fahrenheit
degrees. The upper atmosphere radiates heat into space at this lower temperature which balances the energy absorbed
from sunlight. Global warming is the elevation of the surface temperature of the planet necessary to transport heat
from the surface, primarily due to the LWIR opacity of the atmosphere.
The Average Global Energy Budget accounts for the energy transport described in the previous paragraph. The chart
shows the budget in terms of the incident sunlight which is normalized to 100 arbitrary units. The chart shows that the
Earth’s surface absorbs nearly twice as much LWIR as sunlight and that evaporation reduces the surface temperature
required to transport heat away. The optical properties of the atmosphere are global averages over clear and cloudy
regions.
Biogeochemical processes drive the annual carbon cycle and have removed carbon dioxide from the atmosphere for
billions of years. The oceans remove significant amounts of carbon dioxide from the atmosphere as decaying matter
and carbonates are deposited deep in the ocean out of reach of many biogeochemical cycles. The land is more
productive biologically than oceans because organic materials remain accessible on the surface but this also means
that land plants do not bury or store carbon as efficiently as oceanic processes. Subduction of buried carbon on
oceanic crust recycles carbon dioxide into the atmosphere through magma-fueled volcanic gas eruptions near
continental crust boundaries, partially offsetting the reductions due to photosynthesis. While the loss of atmospheric
carbon dioxide over the billions of years has helped keep the rising solar luminosity from evaporating the oceans,
recent anthropogenic sources have reversed the process and increased atmospheric greenhouse gases. There are many
other biogeochemical processes including nitrogen, phosphorus, sulfur, calcium, silicates, and other mineral and
nutrient cycles. For example, biogenous dimethyl sulfide may have pre-conditioned the land for future invasion by
organisms billions of years ago and it continues to produce cloud condensation nuclei that affect the water cycle.
Where is the carbon on our planet? Only 700 billion metric tons remain in the atmosphere in the form of carbon
dioxide although it may have been one hundred times greater billions of years ago. The oceans have 60 times as much
dissolved gas. Humus, fossil fuels, and dissolved organic matter all have more carbon than the atmosphere. By far the
greatest storehouse of carbon is deep ocean sediments and sediments uplifted from shallow sea floors by plate
tectonics. Biogeochemical processes have played a role in all of these cycles.
Thermal, biological, and geochemical evolution of the Earth’s surface is represented by these graphs that span two
billion years of early Earth history before, during, and after the Archaean Era. The trend toward higher surface
temperatures due to an evolving Sun was offset by a rapid reduction in carbon dioxide greenhouse gas caused by the
rise of photosynthetic bacteria. Rising levels of atmospheric methane from methanogenic bacteria produced a small
opposing effect which is clearly seen on the logarithmic scale. Rising oxygen levels in the Proterozoic Era reduced
atmospheric methane sharply, may have triggered Snowball Earth conditions and led to eukaryote evolution.
The Sun creates, stores, and radiates energy. The structure of the Sun includes the extremely hot dense core where
fusion occurs and radiative and convective zones that are so opaque that the intense and deadly gamma rays and Xrays that radiate in the interior are absorbed and re-radiated for ten million years before their energy is dissipated at
the surface as life giving sunlight. The extreme opacity is essential to maintaining the elevated temperatures that are
essential for protons to overcome their electrical repulsion in sufficient numbers to permit nucleosynthesis to occur for
billions of years. Although classical physics shows that the kinetic energy of the particles is insufficient to overcome
the Coulombic barrier, quantum tunneling under the barrier sustains a slow rate of fusion long enough for intelligent
life to evolve on Earth. Gravitational effects originally transformed the cold dilute gases into a dense hot star leading
to the emergent property of thermonuclear fusion. The Sun evolves because fusion changes the composition of the
core which changes density, temperature, and luminosity.
The Earth creates, stores, and radiates energy. The structure of the solid Earth includes an inner and outer iron core, an
upper and lower mantle, and a lithosphere capped with oceanic or continental crust. Like the Sun, gravitational energy
contributed to the formation of the Earth and to its early internal heating. Rare but powerful radiogenic heat sources
continue to drive chemical evolution and differentiation into layers as well as the many vital processes in the crust and
plates. Additional energy released in the core as the liquid portions cool and freeze solid forms hot spot plumes.
BIO 100 Orientation to Biological Sciences: Introduction to Biological Sciences faculty, department and campus
resources, research opportunities, possible careers, studying science, and current topics in biology.