Discuss the topics you are comfortable with, the topics you struggled with, and how these issues relate to application in your field.
Very early life on land: Just who is this Dickinsonia character, anyway? What it actually resembles is a giant diatom, but that is pretty silly.
Dickinsonia and other Ediacaran Period mya fossils are enigmas. They left fossils in multiple locations world wide, then drop out of the fossil record before the Cambrian explosion in a mass extinction. It is common in the popular press to equate the Ediacaran time as representative of the beginnings of life.
This is not true.
Rather it could be the beginnings of animal life or the beginning of clearly complex multicellular life, but the Earth was already quite alive at this point. The major events are the origin of single-celled organisms and their radiation into archaea and bacteria about mya.
The conventional thought is that this all occurred in the oceans, though there are other opinions. Photosynthetic bacteria showed up around this time, and maybe even were on land. Then, came the evolution of the cyanobacteria about mya which was extremely significant because their brand of photosynthesis produced oxygen as a waste product, and drew down CO2 in the atmosphere.
It is plausible that they colonized land, but because they do not often leave convincing fossils on land, this is hard to prove.
I would love to have Hugo Beraldi-Campesi weigh in on this, as I am out of my depth on this topic. The oxygen produced by the cyanobacteria immediately began rusting all of the iron in the Earths rocks, until this sink was saturated, i.
This phenomenon happened a couple more times, possibly linked to other phenomena like super volcanos. After the last snowball Earth episode, a group of fossils called the Ediacaran fauna turn up supposedly inhabiting microbial mats on seafloors They are known from multiple locations all over the place suggesting global ubiquity.
The Ediacaran animals are not part of this fauna, suggesting an extinction event, and plausibly leaving a bottleneck from which the Cambrian radiation occurred. What if the Ediacarans are not marine animals, and not animals at all?
The interpretation that these are lichens, marine ones s omething that does actually exist todaywas proposed by Retallack What if these were terrestrial organisms — including lichens and other fungi- inhabiting soils?
That is what this new paper suggests Retallack The new bit of information, that will be of great interest to people who read this blog, is the evidence that one key Ediacaran site in Australia the type locality, actually is composed of paleosols, not marine sediments Fig.
The evidence is based on the patterns of oxidation, weathering into soil horizons, isotopic signatures, needle ice, carbonate and gypsum accumulations and cracking……. Could there be biocrusts on land at this point, i.
I think yes, we know cyanobacteria had been around for a very long time, and had all the tools they might need to grow on land UV protection, desiccation tolerance, N-fixation, C-fixation.
That is totally plausible, in fact they could have colonized after other photosynthetic bacteria actually making them terrestrial community version 2.The Geology lab provides students with a laboratory manual, thirty-six rock and mineral samples, a topographic map and other tools to give students a hands-on opportunity to explore geologic concepts covered in the lecture portion of the course as well as virtual field trips related to the geologic sciences.
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