Princeton scientists may have discovered the oldest fossils of animal bodies, suggesting that sponge-like creatures were living in ocean reefs about 650 million years ago. The shelly fossils, found beneath a 635-million-year-old glacial deposit in South Australia, represent the earliest evidence of animal body forms in the current fossil record by at least 70 million years. Princeton geosciences professor Adam Maloof and graduate student Catherine Rose happened upon the new fossils while working on a project focused on the severe ice age that marked the end of the Cryogenian period 635 million years ago. Their findings, published in the Aug. 17 issue of the journal Nature Geosciences, provide the first direct evidence that animal life existed before — and probably survived — the severe "snowball Earth" event known as the Marinoan glaciation that left much of the globe covered in ice at the end of the Cryogenian. When they began the digital reconstruction process, the shape of some of the two-dimensional slices made the researchers suspect they might be dealing with the previously discovered Namacalathus, a goblet-shaped creature featuring a long body stalk topped with a hollow ball. But their model revealed irregularly shaped, centimeter-scale animals with a network of internal canals. After considering a variety of alternatives, the researchers decided that the fossil organisms most closely resembled sponges — simple filter-feeding animals that extract food from water as it flows through channels within their bodies. Previously, the oldest known undisputed fossilized sponges were about 520 million years old, dating to the Cambrian Period.
But evidence has suggested that sponges appeared on the scene much earlier in Earth history. For example, scientists have conducted detailed analyses of genetic material in a wide range of organisms to create "molecular clocks" that suggest how long ago the various types of organisms evolved. According to these clocks, sponges existed millions of years before the Cambrian. This has been supported by the relatively recent discovery of lipid biomarkers — essentially, traces of recalcitrant fats that resist degradation over millions of years — in sedimentary rocks from Oman of nearly the same age as those studied by the Maloof group in Australia.
AP Biology
ReplyDeleteJoey Colvin
Reading this article I noticed several things that were very well presented. One feature was how he incorporated the different time periods of our Earth's history, and how long ago they were. This really helped me understand the interaction of the different organisms chronologically. Another aspect of the review that was well presented was the way the organisms lived. The explanation of filter-feeding animals was really cool, and I found the process very interesting. Finally I thought that the review was very well written, with good grammar and no spelling errors, and a flow that kept me intrigued while reading. One way I think this review could be improved was in the explanation of molecular clocks, as I was kind off confused by them after reading. It would also be helpful to the article if the locations of the previous discovered sponges (520 mya) could be mentioned, as there is possibly an evolutionary connection. When reading this article I was very surprised to hear that a grad student was able to work with her former professor to discover such important information at such a young age.
I like Ryan's review of this article because it is concise, and tells the reader what he or she needs to know without being repetitive or redundant. I also liked Ryan's review of this article because it provided dates which makes this information all the more interesting and informative. Finally, in his review of the article, Ryan provides us with research based evidence, saying that sponges were said to have been around long before the cambrians, and he also tells us about the "molecular clocks", which makes all of this fossil dating make more sense.
ReplyDeleteI think that this review could have been improved by being broken up into more paragraphs. The fact that the first paragraph is so long makes it a little more confusing. Also, i think that he could have explained more about what the Cryogenian age was. I think that one reason why this article is impressive is because it shows us how we are still discovering new things today, even after hundreds of years of research. It reminds us that although we think that we know everything now, we will look back in the future and realize how much we are discovering every year.
Ryan's review excelled at many points. His review of the article was very concise. He presented information in a well stated and timely manner and eliminated excess fluff. Information was presented that was necessary. All the dates, times and references provided were necessary and help add to the review of the article. He had no more or no less than what he needed to tell. Ryan’s review also excelled very well at providing relevant background information. If the information in the article was not presented with background information then the reader would be lost and unable to understand the importance of the findings. By stating background information such as “Previously, the oldest known undisputed fossilized sponges were about 520 million years old, dating to the Cambrian Period. “ This gives the reader a reference point to compare the new sponge findings. Ryan also provides relevant information on sponges and dates. Another thing Ryan did well in the article was provide intriguing information for the reader. By adding parts about “molecular clocks” he hinted at much larger and bigger areas of science that the reader could continue to pursue if he was interested. These tidbits help add dimension to his review.
ReplyDeleteThe review could be made better in two ways. One way that it could be better is if it was lengthier. The article gave a very good outline of the findings and of its significance, but the reader would really like to know more. If more in depth knowledge was provide and greater detail given, then the review could be much better. Another thing he could do is provide personal anecdotes. Personal anecdotes could allow the reader to connect more with the story. Writing in the first person could provide a more familiar argument for the reader. One thing I was impressed by was the molecular clocks in the article. This impressed me because I am astounded by how far science has come to be able to chart a genetic pathway for every organism. Using this pathway, scientists may be able to trace evolution more accurately. The article was well written and concise.
The build-up of facts leading up to a conclusion in the review was very well presented. It made all of the facts work to captivate the reader. By presenting all those details in succession, the article adds more and more to the interesting topic of the article. Another important aspect that was well presented was the use of interviews to add more information. It made the review almost into an article itself. The use of paragraphs to show contradicting view points was very good and showed that there was a thought process behind the review and that it wasn’t a mindless summary of facts.
ReplyDeleteThere were a few things that I found that could be improved. Firstly, the lack of opinion about the article makes the review only slightly better than a regular summary. The lack of personality to the review made it seem like an article itself. Secondly, the review shouldn’t contain every single fact that an article presents because it can ruin the article for the reader.
A very interesting fact of this article was the notion that everything we thought was true about the evolutionary clock could possibly be changed if certain facts are uncovered. It clearly won’t disprove anything substantial but it is important to note that our sense of evolutionary time might shift given what we now know.