QUOTE(hairston630 @ Sep 24 2007, 11:37 PM)
I have another....
On the cambrian explosion
According to the evolutionary model, benthic animals should have appeared during the early Cambrian [explosion], followed much later by pelagic organisms. Increased predation of bottom dwellers was, presumably, the “evolutionary” driving force behind marine creatures’ transition to the open sea. The open-sea environment allows for greater safety and avoidance of predatory attacks. Moreover, the activity of benthic organisms, over time, would have increased the nutrient levels in the open sea, eventually making way for occupation of this niche.
A duo of paleontologists from France and China have published findings that stand in sharp contrast to these evolutionary expectations.7 By examining newly available fossil specimens of a long-extinct marine crustacean (Isoxys) having unusually well preserved soft-body parts, the French and Chinese paleontologists found that Isoxys occupied an open-sea environment. The Isoxys specimens revealed swimming appendages, visual organs, and shell design all consistent with those expected of an organism living in the open sea.
The recovery of Isoxys from early Cambrian rocks makes this discovery even more remarkable. Pelagic lifestyles could not have evolved from benthic lifestyles. Rather, the fossil record shows that exploitation of both the open sea and sea floor occurred simultaneously. Moreover, the shell design of Ixosys displays long spines extending from the anterior and posterior ends. These spines would not have contributed to Isoxys buoyancy, and therefore, must have served as defensive structures in the face of open-sea predatory threats—again, an unexpected finding.
As paleontologists develop an increased understanding of the Cambrian ecology, they find more and more evidence that the ecosystems of that time were complex, expansive, and highly integrated. The first complex animals possessed surprisingly advanced capabilities, enabling them to exploit the full range of ecological niches. Doesnt this seem to raise a challenge?
Fazale Rana, "Extinct Shell Fish Speaks Today"
Jean Vannier and Jun-Yuan Chen, “The Early Cambrian Colonization of Pelagic Niches Exemplified by Isoxys (Arthropoda),” Lethaia 33 (2000): 295-311.
Fazale Rana and Hugh Ross, “The Cambrian ‘Explosion’ and Why It Means So Much for Christians,” Facts for Faith (Q2 2000), 15-17.
Simon Conway Morris, “The Cambrian ‘Explosion’: Slow Fuse or Megatonnage?” Proceedings of the National Academy of Sciences, USA 97 (2000): 4426-29.
Simon Coway Morris,“The Community Structure of the Middle Cambrian Phyllopod Bed (Burgess Shale),” Paleontology 29 (1986): 423-67.
Steven J. Gould, Wonderful Life: The Burgess Shale and the Nature of History (New York: W. W. Norton, 1989), 222-24.
Philip W. Signor and Geeret J. Vermeij, “The Plankton and the Benthos: Origins and Early History of an Evolving Relationship,” Paleobiology 20 (1994): 297-319.
Vannier and Chen, 295-311.
I am not an expert on Cambrian life, so maybe Cimber might have some more to add. Both Sean and Questionmark's posts were very good as well, you should be sure to read through the links they provided. I think it's also important to note, that the word explosion is a somewhat misleading term, as it describes a period of time over
millions of years.
I dont think this poses a problem at all. It just gives us a more refined time scale that things occurred. It also tells us complex life is older than we thought. As per you source
QUOTE
The presence of Isoxys in the Maotianshan Shale of S. China indicates that arthropods had already colonized midwater niches by the Early Cambrian. The midwater communities of the Maotianshan Shale comprised numerous other invertebrates, such as abundant medusiform eldonids, vetulicolids, chordates and possibly early vertebrates. This contradicts the opinion that pelagic communities remained poorly developed until late Cambrian/Ordovician times and that the occupation of the midwater niches largely post-dates the initial diversification of the benthic faunas.
Here is part of their conclusion, which I see poses no problem to evolution, only a refinement of time lines.
QUOTE
Isoxys is certainly not the only organism to have colonized pelagic niches during the Early Cambrian. The Maotianshan Shale biota contains a number of other pelagic candidates or occasional swimmers. The eldonids, a group of medusiform eucoelomates were probably the most abundant midwater organisms with capabilities for buoyancy regulation. Anomalocarids
were active swimmers and macrophagous predators of possibly both epibenthic and midwater invertebrates (Chen et al. 1995; Hou et al. 1995; Chen & Zhou 1997; Chen et al. 1996). The enigmatic vetulicolids (e.g. Vetulicola cuneatus; Hou 1987, Chen et al. in prep.) were also members of the midwater communities but were not predators. Morphology indicates that early
chordates (Chen et al. 1995) and possibly vertebrates (Shu et al. 1999), well represented in the Maotianshan Shale biota, were probably nektonic ®lterers (Chen et al. 1999). This provisional inventory indicates that several animal phyla had already invaded the midwater environment by Early Cambrian times. This contradicts the opinion (Signor & Vermeij 1994) that pelagic
communities remained poorly developed until late Cambrian/Ordovician times and that the occupation of the midwater niches largely post-dates the initial diversi®cation of the benthic faunas.
Jean Vannier and Jun-Yuan Chen, “The Early Cambrian Colonization of Pelagic Niches Exemplified by Isoxys (Arthropoda),” Lethaia 33 (2000): 295-311.
Jean Vannier and Jun-Yuan Chen, “The Early Cambrian Colonization of Pelagic Niches Exemplified by Isoxys (Arthropoda),” Lethaia 33 (2000): 295-311.
As for the reasons source, From a quick read I can see that it is someone "out to get" evolution with no real understanding of what they are talking about, though I am not a biologist I can point out several flaws or incorrect statements made by the author.
QUOTE
China’s rich cache of fossils provides paleontologists with a window to the time in Earth’s history when complex animal life first appeared. As scientists peer through this window, they see a scene that defies naturalistic explanation.
The fossils discovered in China, along with those in British Columbia and elsewhere, present an unexpected picture: nearly every animal phylum ever to exist in Earth’s history appeared suddenly about 540 million years ago.
1 The author is rather dubious here, she/he quotes their source for this as themselves to an article that is neither peer-reviewed nor even hosted by the website anymore for that matter. There are many missing phyla from the Cambrian. A phylum refers to the level in the biological classification system describing an organism’s body plan or architectural makeup.
Phylum refers to a taxonomical division by internal plan. Also, looks can be deceiving, Which is why classifications are not done solely on looks alone. Some paleontologists report that more than seventy animal phyla (strictly marine animals) appeared in less than 2-3 million years. Scientists refer to this dramatic introduction of animal phyla as the Cambrian Explosion—biology’s “big bang.”
I would like to see where she pulled this from, it is not cited. Low end estimates of the Cambrian explosion range from 5 million years, they go up to 40 million years. As far as I am aware no one is claiming these phyla came into existence in 2-3 million years.Paleontologists had thought the Cambrian event involved only invertebrates (organisms lacking a backbone). However, the recent discovery of jawless vertebrates from the lower (earlier) Cambrian deposits in China changed their view. Researchers must now account for the simultaneous appearance of both groups.
2 Here she flat out lies too or purposefully deceives her readers. Here source says it all with this quote from their conclusion:
QUOTE(Shu et al.)
The major steps in the early evolution of chordates may well have occurred in the late Neoproterozoic. To date, however, no suitable fossil candidates have been identified amongst the Ediacaran assemblages, although preservation in siltstones and sandstones is less conducive to survival of delicate soft-bodied taxa. Our discovery, however, gives no reason to suppose that the origin of vertebrates was hundreds of millions of years earlier, and the reliability of the methods used to reach such a conclusion has been questioned elsewhere.
The phylum Chordata holds special interest for paleontologists researching the origin of animal life. Chordates include all vertebrates (fish, amphibians, reptiles, birds, and mammals) and some invertebrates. To understand the origin of chordates, therefore, is to understand the beginning of some of the most important organisms in Earth’s history. For this reason, evolutionary biologists peer eagerly through this window of time. They especially hope to see the connection between chordates and the other invertebrate phyla.
According to the most widely accepted evolutionary model, echinoderms (sea stars, sea cucumbers, etc.) gave rise to chordates (and to hemichordates, as an evolutionary side-branch).3 This model posits that a sessile (attached to the seafloor) echinoderm brought forth a sessile chordate (classified as a urochordate), similar to modern-day tunicates (sessile invertebrates with a free-swimming larval form). The urochordate then gave rise to a free-swimming cephalochordate, which in turn produced jawless vertebrates, followed by jawed vertebrates.
The prediction for the fossil record, in light of the evolutionary model for chordate origins, calls for echinoderms, urochordates, hemichordates, cephalochordates, jawless vertebrates, and jawed vertebrates to appear sequentially. Given the extensive differences among these groups, their first occurrence in the fossil record should be separated by long time periods, much longer than the 2-3 million years shown by the Cambrian Explosion.
Again, no one is claiming it was 2-3 million years but her. Also it is important to note that while this a suspected path to vertebrates it is exhaustive. Any evidence contrary to this would not disprove evolution, but rather make our understanding of it more accurate. So while she poses a question as to whether this is the correct sequence of groups, it does nothing to help "disprove evolution"The China discoveries show, instead, the co-existence of echinoderms, hermichordates, cephalochordates, and jawless vertebrates in the earliest part of the Cambrian era.
4 Again she sources herself for this, which is a rather large claim. If it is true why not source something as accepted as an annual review, which is normally done by the top people in the field. At this point, her credibility has taken another huge hit. And I think it should be important to be noted, I have a pretty extensive research Database, I have never heard of the Journal Connections. I cannot find any mention of it in all the journals the university I work for has access too, only mention to a magazine, which is not peer-reviewed. And now Chinese paleontologists have added urochordates to this list with the discovery of a tunicate in lower (earlier) Cambrian rocks.
5 Before the Cambrian era, no such animal groups existed on Earth. In other words, early in the Cambrian period, when complex animal life first appeared, the kinds of creatures that should have given rise (according to evolutionary theory) to the jawed vertebrates emerged concurrently.
From Shu's Paper
QUOTE
Urochordata are believed to represent the most basal chordate branch within Chordata11,26; however, whether the ancestral chordates were free-swimming or sessile has been a long-standing question18,26,27. Traditional hypotheses hold that vertebrates evolved by paedomorphosis from a urochordate-like larval stage, and that the ancestor of chordates would have resembled a sessile lophophorate12,13,27. Recent models, supported by molecular data, posit a free-swimming ancestry of chordates, including urochordates28±30. Fossils may preserve combinations of characters not seen in extant groups, and so are crucial for testing schemes of how characters were acquired in the origin of new body plans. The interpretation of the present specimen, as possessing oral tentacles comparable to those seen in lophophorates, is consistent with traditional viewsÐif not modern, molecule-based hypothesesÐbut a single example is far from being conclusive. Further palaeontological and molecular work is needed to investigate the problem.
Does not sound too problematic to me, only a possible refinement of knowledge. Also It sounds as though she is viewing the progression as a linear one. First one then it becomes extinct and the other arises. This may not be the case, Lets say we have two populations living in different areas, both the populations belong to the same species. If the populations are seperated then there is no problem with changes occurring to both simultaneously. To compound this problem, Chinese paleontologists now recognize an additional phylum (Vetulicolia) as part of the Cambrian event.6 This taxa’s features place it at the base of the chordate evolutionary tree. This makes the Cambrian explosion that much more dramatic. In the words of the Chinese scientists, “the co-occurrence of stem-group deuterostomes [Vetulicolia] and agnathan [jawless] fish are consistent with an ‘explosion’ of metazoan body plans in the latest Neoproterozoic and early Cambrian.”7
What researchers see as their view through the window of time grows clearer is the sudden and simultaneous appearance of echinoderms, hemichordates, urochordates, cephalochordates and jawless vertebrates in the fossil record. This image, with its observable data, confounds a naturalistic explanation but conforms to a biblical creation model that asserts the divinely orchestrated introduction of complex animal life on Earth.
1. Fazale Rana and Hugh Ross, “The Cambrian ‘Explosion’ and Why It Means So Much for Christians,” Facts for Faith 2 (Q2 2000), 15-17.
2. D. –G. Shu et al., “Lower Cambrian Vertebrates from South China,” Nature 402 (1999): 42-46; Jun-Yung Chen et al., “An Early Cambrian Craniate-like Chordate,” Nature 402 (1999): 518-22.
3. Cleveland P. Hickman, Sr. et al., Integrated Principles of Zoology, 6th ed. (St. Louis, MO: The C. V. Mosby Company, 1979), 476-81.
4. Fazale R. Rana, “Cambrian Flash,” Connections, vol. 2, no. 1 (2000), 3; Fazale “Fuz” Rana, “Extinct Shell Fish Speaks Today,” Connections vol. 3, no. 2 (2001), 1-2.
5. D. –G. Shu et al., “An Early Cambrian Tunicate from China,” Nature 411 (2001): 472-3.
6. D. –G. Shu et al., “Primitive Deuterostomes from the Chengjiang Lagerstatte (Lower Cambrian, China),” Nature 414 (2001): 419-24.
7. D. –G. Shu et al., “Primitive Deuterostomes,” 419-24.
Ill have to finish the rest later, I have to go to a meeting. Hope that helps.
. Neph, the sources you supplied were written by third-graders. You have shown nothing but anti-intellectualism. There is no science whatsoever contained in your sources. This YEC at their finest.
) I don't think that any one thing is the cause of a mass extinction, I think mass extinctions are probably caused by numerous things (especially since we have decent evidence that many of these proposed hypothesis were all occurring around some of the extinction events). I think it would be more a combination of natural climate shift, hit with a meteorite (which would accelerate dramatic climate changes), possibly nearby GRBs, etc. You start combining two or three of these possible culprits then you have some very real, very complex, real world scenarios. 
Yeesh! You should know that!