What is the next level after phylam?

Answer 1

Introduction sorry for all the info i hope that's what ypu wanted????

Anti-evolutionary apologists have long claimed that the lack of transitional forms between higher taxonomic ranks is evidence of creation. Gish (1993, p. 135) writes:

"The fossil record is powerful, positive evidence for creation, and every new discovery strengthens the case for creation and exposes additional difficulties for evolutionary theory. Evolutionary theory is, of course, dead, as long as the two huge gaps between single-celled organisms and the complex invertebrates and between complex invertebrates and fishes continue to exist. The total failure to reduce these gaps, let alone close them, in spite of an intense search by thousand of paleontologists during more than 125 years, establishes beyond doubt that the required transitional forms will never be found. The fact that the gaps between all higher taxa, such as families, orders, classes, and phyla, are systematic and almost always large, is simply additional confirmatory evidence for creation."

Phillip Johnson (1998) writes:

�The "Cambrian Explosion" is the sudden appearance of the major animal groups (phyla) in the rocks of the Cambrian era, without apparent ancestors. As Dawkins himself has put it, "It is as though they were just planted there, without any evolutionary history." Of course, Dawkins and all other Darwinists believe that this appearance is an illusion caused by the incompleteness of the record, and that a complete fossil record would show a universe of transitional forms and side branches, all having evolved by tiny steps from a single common ancestor. Gould raises a radically different possibility. He explains that there are two possible explanations for the absence of Precambrian ancestors: "the artifact theory (they did exist, but the fossil record hasn�t preserved them), and the fast-transition theory (they really didn�t exist, at least as complex invertebrates easily linked to their descendants)."

Stephen Robinson (1998, p. 3) writes:

�The sudden profusion of marine life in the Lower Cambrian is commonly referred to as �the Cambrian Explosion�. In the space of about 5 million years, most extant phyla and classes of marine invertebrates as well as others that did not survive even the Cambrian suddenly appeared out of nowhere.�

This view is widespread among young and old earth creationists. But is it true in light of modern data? What I will attempt to show in this note is that the �gaps� in the evolution of Cambrian life forms are now being filled in by data obtained over the last 15 years; much of this data coming in within the past 2 years. While there are older interpretations of the Precambrian animals as being totally unrelated to modern animals(such as Seilacher's Vendozoan hypothesis), the newer data is showing evidence of relationships between the Ediacaran fauna and that of the early Cambrian. We will look at the evolutionary sequences which lead from Precambrian worm-like creatures to the arthropods, molluscs, brachiopods, and annelids, four different phyla.

Secondly, I will show that it is absolutely false that the majority of animal phyla appeared in the Cambrian. While this is widely stated by apologists and paleontologists, it is actually an assumption not borne out by the data.

Definition

Before we can discuss phylum level evolution, we must know what a phylum is. A phylum is a group of animals sharing a similar body plan. Gilbert states(1991, p. 831):

�Only about 33 animal body plans are presently being used on this planet (Margulis and Schwartz, 1988). These constitute the animal phyla.�

There are a couple of cautions about the use of the term phyla. A phylum is assigned to a given creature based upon its having the shared characteristic body plan. Occasionally, however, different body plans are not assigned different phyla and this creates an appearance that phyla can't evolve. A case in point concerns a deep-sea sponge which is classed with the Porifera in spite of the fact that it has an entirely different body plan. Vacelet and Boury-Esnault (1995, p. 335) relate:

�Our results raise fundamental questions about the validity of characteristics used to distinguish the phyla of lower invertebrates. A sponge is defined as a �sedentary, filter-feeding metazoan which utilizes a single layer of flagellated cells (choanocytes) to pump a unidirectional water current through its body. Except for being sedentary, the cave Asbestopluma and presumably all Cladorhizidae lack these basic sponge attributes. In an extreme environment where active filter-feeding has a low yield, cladorhizids have developed a mode of life roughly similar to that of foraminiferans or cnidarians. Their feeding mechanism relies on passive capture of living prey and on transfer of nutrients into the body through intense cell migrations, the analogue of cytoplasmic streaming in foraminiferan pseudopodia. This may be compared to the emergence of macrophagy in abyssal tunicates, also accompanied by a reduction of the filtering system although in Cladorhizidae the result is more extreme, with a main body plan different from Porifera and resembling no other modern anatomical design.�

�Such a unique body plan would deserve recognition as a distinct phylum, if these animals were not so evidently close relatives of Porifera. Their siliceous spicules show clear similarities to several families of poecilosclerid Demospongiae.�

In cases like that above, the lack attribution of phylum rank for these 'sponges' hides the fact that the Porifera may very well have given rise to an independent phyla. The only real connection between the two groups are the spicules which act as evidence of common descent. If the Cladorhizid sponges were to lose the spicules, the connection between the two groups would be lost. Body plans are obviously more of a continuum and difficult to separate than the simplistic concept of phyla espoused by anti-evolutionists would imply.

Phyla were defined more than a century ago based upon descriptions of modern fauna. Using this schema forces ancient animals to be included in one of the modern phyla and ignores the possibility of phyla-level evolution. The problem is similar to that of describing a tree only by examining the very tips of the branches and not looking at the trunk. This makes the concept of a phyla time-reversed. It is forcing present concepts back into the past, which is not the way that evolution was supposed to have occurred.

One further definition. It must be made clear that we are discussing multicellular animal life. There is evidence for multicellular algae going back much further in time.

The Setting

The Cambrian/Precambrian boundary is no longer considered as the place where life suddenly appears. There is a continuum of life across this boundary. Grotzinger et al (1995, p. 603-604) write:

"Once held as the position in the rock record where the major invertebrate groups first appeared, the Precambrian-Cambrian boundary now serves more as a convenient reference point within an evolutionary continuum. Skeletalized organisms, including Cambrian-aspect shelly fossils, first appear below the boundary and then show strong diversification during the Early Cambrian. Similarly, trace fossils also appear first in the Vendian, exhibit a progression to more complex geometries across the boundary, and then parallel the dramatic radiation displayed by body fossils."

Evidences of macroscopic life forms are now found as early as 680 myr ago in the form of worm burrows (Pagel, 1999, p. 881). And several modern phyla are now claimed to appear in the Precambrian and thus are not part of the supposed 'Cambrian Explosion.' These are:

Phylum Porifera (Sponges Brasier, Green and Shields, 1997, p. 303)

Phylum Mollusca (Fedonkin and Waggoner, 1997, p 868)

(This may be a proto-Mollusc rather than a true mollusc--Campbell 2001)

Phylum Annelida (Cloud and Glaessner, 1982, p. 788)

Phylum Cnidaria (Conway Morris, 1998, p. 29)

Phylum Arthropoda (Waggoner, 1996, p. 190)

For a chronology of the events surrounding the Cambrian/Precambrian boundary see:

Cambrian/Precambrian Chronology

One final issue must be discussed before examining the paleontological evidence. What is a transitional form? Anti-evolutionists say they don't exist but they often don't define what it is that doesn't exist. A transitional form is an animal that will share traits between the two different groups. For instance, an animal that is transitional between worms and arthropods has both worm-like and arthropod-like traits. It is very difficult to classify such an animal because it doesn't quite fit the definition of either group. So, it is unfair to insist that the animal be classified in one or the other groups and then claim that there are no transitional forms. Due to the vagaries of fossilization, it is not expected that we will ever find animals which are on the direct line between the two groups, and if we do find an animal on the direct line, it is not clear that we would recognize it as such. So what we have in the fossil record are animals that are close to the line of descent. But even these animals will show many of the traits that were involved in the actual line of descent between the two phyla. Some might claim that this is cheating. It isn't. Even if we found the individual animal that is on the direct line of descent between two groups, we would not have any way of knowing that. Thus, we must treat all transitional forms as if they are near to the actual line of descent.

One can not determine entirely, what a transitional creature would look like by examining modern animals. You can't determine what your grandfather looked like by averaging between your appearance and that of a cousin. While there might be some similarities, such an averaging will not reproduce the picture of your grandfather. Nor will it reproduce an average in appearance between your grandfather and grand mother! A transitional form must be transitional between the phyla at the contemporary time of the split between the phyla

Worms

In the late Precambrian, the Vendian Period (620-540 myr ago) to be exact, worm burrows become increasingly numerous. Indeed, recently, larvae of segmented worms have been found in the Doushantuo formation of China (570-520 myr; Bengtson and Zhao, 1997, p. 1645). Since just prior to the Vendian the only evidence for macroscopic life was that of the worms, if the various phyla were to evolve, it must have been from the worms.

Arthropods

The first in the line leading from worms to arthropods is an animal similar to the lobopod, Aysheaia. It can be seen at

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and

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