- New Evidence on the Origins of Life on Earth
- Evolutionary history of life
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- The ancestor of all organisms
- Origin of Life: Early Earth Environment
This was a period of intense meteor bombardment sustained by our planet about 3. This is significantly earlier than the currently accepted oldest fossil evidence would suggest estimating 3. The oldest confirmed fossils are from about 3. However, scientists have so far been unable to confirm that. Some researchers think it would have been impossible for life to survive the late heavy bombardment, so that our oldest ancestor must be from after this phase.
New Evidence on the Origins of Life on Earth
There are claims that the event would have sterilised the plants and vaporised any water around at the time. However, there are some recent mathematical models which suggest that pockets suitable for life could have remained. We found that the crown groups of the two main lineages of life — bacteria and archaea — appeared almost one billion years after the last common universal ancestor. This finding is consistent with previous studies. This important event in the history of the eukaryotes occurred close to when they first appeared, suggesting that it helped to drive their subsequent rapid spread.
A contemporary Robinsonade — York, York. The polar oceans and global climate — Milton Keynes, Buckinghamshire.
Edition: Available editions United Kingdom. Holly Betts , University of Bristol. Students can produce a skit involving an imaginary meeting between Darwin and Mendel, create a newsletter to distinguish factual data from guesswork, evaluate web sites that deal with evolution… and more!
Evolutionary history of life
September Evolution theory explains how organisms have changed over time. Natural selection guarantees that the fittest are most likely to pass on their genes. Conclusions: Current evidence and historical data show that evolution is both a fact and a theory. Evolution: Fact and Theory. Students create a journal entry and birthday card that describes the ecology of a particular geological time period.
The Selfish Gene. Cooper, and R. Science on Trial: The Case for Evolution. Pantheon, New York. Norton, New York. Lederberg, editor. Encyclopedia of Microbiology, 2nd edition. Academic Press, San Diego. Korona, R.
- Evolution: Fact and Theory.
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Lenski, F. Marsh, and L. Times Books, New York. Schneider, J. Meier-Eiss, W. Arber, R.
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- 3.8 billion years ago?.
- Early Earth Environment.
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Content Areas biodiversity environment genomics biotechnology evolution science policy. However, as the earth cooled, gravity-trapped water vapor condensed, fell as rain, and did not boil away but remained impounded in pools that became lakes and oceans. It was also believed that tectonic activity caused many volcanic eruptions at that time. From present-day volcanoes, we know that when they erupt, they release carbon dioxide, nitrogen, and a host of nonoxygen gases. In addition, with no protecting atmosphere, the earth was constantly bombarded with meteorites and other space debris still in circulation from the big bang.
From current astronomical research, we know that meteorites can carry ice and other compounds, including carbon-based compounds. Researchers believe, therefore, that early Earth's atmosphere consisted of water vapor, carbon dioxide, carbon monoxide, hydrogen, nitrogen, ammonia, and methane. Note that no oxygen was present in early Earth's atmosphere!
The ancestor of all organisms
Meteorologists suspect that lightning, torrential rains, and ultraviolet radiation combined with the intense volcanic activity and constant meteorite bombardment to make early Earth an interesting but inhospitable environment. Two American scientists, Stanley Miller and Harold Urey, designed an experiment to simulate conditions on early Earth and observe for the formation of life.
They combined methane, water, ammonia, and hydrogen into a container in the approximate concentrations theorized to have existed on early Earth. To simulate lightning, they added an electrical spark. Although this experimental design probably did not accurately represent early Earth's percent of gaseous combinations, further work by Dr. Miller and others, using different combinations, all produced organic compounds. However, to this date, no living things have been made from nonliving things in the laboratory.
Interestingly, continuing research on meteorites has identified, as recently as , that they contain all five of the nitrogen bases. This presents the hypothesis that perhaps the ingredients necessary for life were brought from outer space! By looking at a modern-day map of the world, it is easy to see how the coastline of the west side of Africa appears to match the east coastline of South America. As cartographic skills and knowledge of the continent's boundaries increased by nautical exploration, in , German meteorologist Alfred Wegener proposed an Earth-moving hypothesis.
Origin of Life: Early Earth Environment
He hypothesized that the existing landmasses are actually moving and probably all began as one large landmass. His theory of continental drift made the landmasses of Earth appear like giant floating islands sometimes moving away, sometimes crashing into each other by forces he could not describe. Although the Africa-South America anomaly was noted, his theory did not gain much support in his lifetime. The large Pacific plate rubs against the North American plate at the San Andreas fault in Southern California, creating frequent earthquakes. With recent advances in geology, we now know that all the surface features—land and water—are actually floating on the viscous mantle of the earth, which supports the movable crust and outer layer of Earth.
The solid crust, or plate, that we inhabit is one of many irregularly shaped pieces of varying size that move in specified directions.