Natural Science II – ERTH 1040 Evolution – Life Through Time J. D. Price
Evolution remains at the center of controversy in many communities. Oklahoma, Alabama, Kansas, Virginia are some of the states that have taken political action to devalue this theory in science education Here’s the approved statement for biology textbooks in Oklahoma (1999): Message from the Oklahoma State Textbook Committee: This textbook discusses evolution, a controversial theory, which some scientists present as scientific explanation for the origin of living things, such as plants and humans. No one was present when life first appeared on earth. Therefore, any statement about life's origins should be considered as theory, not fact. The word evolution may refer to many types of change. Evolution describes changes that occur within a species. (White moths, for example, may evolve into gray moths). This process is micro evolution, which can be observed and described as fact. Evolution may also refer to the change of one living thing into another, such as reptiles into birds. This process, called macro evolution, has never been observed and should be considered a theory. Evolution also refers to the unproven belief that random, undirected forces produced a world of living things. There are many unanswered questions about the origin of life, which are not mentioned in your textbook, including: Why did the major groups of animals suddenly appear in the fossil record, known as the Cambrian Explosion? Why have no new major groups of living things appeared in the fossil record in a long time? Why do major groups of plants and animals have no transitional forms in the fossil record? How did you and all living things come to possess such a complete and complex set of instructions for building a living body? Study hard and keep an open mind. Someday you may contribute to the theories of how living things appeared on earth.
Theory is the basis of science Theory is necessary because it is impossible to observe all systems in all places at all times (as you are reading this you are theoretically generating a myriad of proteins – this is theoretical, because you are not actually evaluating your body chemistry). “Fact” or “Truth” is the goal of every Scientific Theory Some Theories have more lines of evidence The evidence for the Theory of Plate Tectonics comes from a number of places and times, over several length scales. As of now, we have only one example of the origins and development of life. Models built on one example can be internal consistent, but not externally verifiable.
What of life’s origins Science • The Earth has rocks that yield radiometric dates of 4 Ga, and is routine struck by meteorites with dates of 4.5 Ga • Remains of life are found in rocks 3.5 Ga and younger • Remains start simple, become more complicated over time Non Science • My belief and value system holds a religious text to be literal and inerrant. Therefore, our perception of old life on the Earth is incorrect. Pseudoscience • Scientific discovery should prove my beliefs to be true. • All inconsistencies with my preconceived notion must be wrong.
If you believe in the Genesis account recorded in Judeo-Christian scripture as literal natural history The correct is response is: The Earth may look old and life may look interrelated, but I believe life developed from a supernatural source (a non-science philosophy) Not: The Earth does not appear old and/or life does not appear interrelated, and I will attempt to use natural processes to show how the supernatural act occurred. (a pseudoscience philosophy) The latter is the modus of so-called “creation science” and “intelligent design”: which typically call on unique physical processes to maintain a consistency with the Genesis text.
So, my disclaimer (based on the one for Oklahoma): Message from Dr. Price: This lecture discusses evolution, a scientific theory, much like the theories developed for gravitation, electrical conduction, magnetism, the parts of an atom, covalent bonding, the dissolution of ions, plate tectonics, lithification of sediments, grain boundary energy, the interaction of trophic systems, genotypes, and protein synthesis. In each case, explanations are made to explain observations; these are tested repeatedly and refined such that each approaches universality (applicable anywhere at any time). No person was present when life first appeared on earth some 3 or more billion years ago. However, an extensive record of the remains of ancient biota are preserved within the rocks of the near-surface of the earth. The oldest demonstrable fossils are morphologically similar to modern unicellular life. With increasing time, the diversity of life increases substantially: fossils record more complicated multicellular organisms, and fossils become increasingly prominent in rocks formed subareally as well as those formed in aquatic environments. Perhaps more substantially, all life on earth shares common characteristics and chemistry. All living things contain long chains of deoxyribonucleic acid that interface with ribonucleic acid to produce complex molecules, called proteins, out of 20 amino acids. Changes in the sequence of deoxyribonucleic acid occur through several processes; such changes can be dramatic on relatively short time scales, and are logically thought to be extensive when considering geologic time. All living things respire and regulate respiration, grow, respond to stimuli, and may reproduce. Changing conditions, such as the result of a dynamic lithosphere, hydrosphere, and atmosphere, largely fueled by the nonrandom conditions of imposed by a cooling planet revolving around a planetary body massive enough to fuse hydrogen into helium, may support certain genetic codes at the expense of others. There are many unanswered questions about the origin of life, which are not answered by our current understanding of the Earth, including: Why did life become rapidly diverse in rocks dating from 540 million years ago? What is the nature of transition in life diversity? How did you and all living things come to possess such a complete and yet simple sequential set of instructions for building a living body? Study hard and keep an open mind, and actually learn how to evaluate observations scientifically. Someday you may contribute to the theories of how living things appeared on earth.
In short: creation science and intelligent design are not science - they are philosophies They have no legitimate place in a science class.
Domains of Life Analyses of DNA make it suggest that all of life on Earth is related back to one single organism. Chemically, we’re all very similar.
The remnants of many organisms are left behind in accumulating sediments. Skeletal materials, made of dense minerals can be particularly well preserved. In places entire ecosystems are buried and lithified. Note: these are categorized by morphology and environment (not genetics) Q: what type of rock is this?
Keep in mind the fossil record is by no means an accurate depiction of ancient life Fossilization favors Organisms with simple skeletons (few pieces) in aquatic environments with rapid depostion that are small enough to buried quickly that are abundant and well distributed that existed over substantial periods of time Note the oldest observed fossil certainly may not be the oldest individual for that organism Note fossils contain no organic materials; there is only a little chemical evidence to be gleaned from them.
Solar System Formation 4.6 billion years ago Q: From what materials is our solar system made?
The Moon shows evidence of heavy bombardment up to 3.8 Ga Undoubtedly, the Earth is being impacted simultaneously – the impacts would make the surface of the Earth unsuitable for liquid water. Life is not likely to arise until frequent impacts cease.
Or maybe not… Recent evidence shows that the oldest materials on earth, Jack Hills Zircons, are 4.4 biliion years old. These record crystallization temperatures in the 600-750 ºC range - implying wet magmatic conditions and the possible establishment of the hydrosphere. NASA’s Earth Observatory
But prior to 4.4 Ga, there are a number of problems with the early Earth. • Very hot • Frequent inputs of high kinetic energy • Weak atmosphere • Sunlight reduced at surface • No liquid water at surface (and little fluid water at depth) • No complex organic molecules All except last are reduced through gravitation and kinetics. The last is trickier although helped by cooling temperatures.
In 1953, Miller and Urey conducted an experiment in which methane, ammonium, hydrogen, and water were subjected to an electrical discharge. After a week, 10- 15% of C formed organic compounds, 2% as amino acids. Suggests that a primitive atmosphere could produce life compounds.
Remember these? Meteorites called carbonaceous chondrites The juxtaposition of very high temperature components (chondrules and inclusions made of silicates) and very low temperature components (complex carbon compounds).
Figure 24.24 24-515
Amino acids are a long way from proteins and nucleic acid The next step is the subject of ongoing investigations. One current theory: the RNA world RNA has the ability to copy itself, modify as an enzyme, and bond with amino acids. Many viruses proliferate with nothing more than RNA and protein (although few think viruses were the first life – too dependant on cellular life) Q: what’s the next step and why?
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