Life on Our Evolving Planet

Life on Our Evolving Planetslide notes

The entire slide show is on my website at 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.

I retired from a twenty year career as an optical physicist designing and analyzingaerospace 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 teachinga solar and global evolution course. I am also a research scholar in residence.
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.
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?
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.
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 formedby 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=mc2) 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.
The composition of the Sunis 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.
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.
Bacteria and mammalsconsist 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.
Seawater and the dryatmosphereconsist 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 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 andcollected 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 besubdivided 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.
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.
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).
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.
A traditional geologic time scale (circa 1983) emphasizes the Phanerozoic Era whose rich fossil record followedthe 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.
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.
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.
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.
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.
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.
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%.
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.
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 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”.