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Phylogenies Perfect Paragraph

Submitted by sditelberg on Thu, 05/02/2019 - 13:05

With regard to the carnivorans, the character "tail" has two states. In this phylogenetic analysis, an elongated tail is the ancestral character state (scored with a 0) and a short tail is the derived character state (scored with a 1). In phylogeny A, a short tail is hypothesized to have evolved after the split between otters and the taxa of bears, sea lions, walrus, and seals. This relationship proposes that a short tail is the synapomorphy for the monophyletic group of bears, sea lions, walrus, and seals. In phylogeny B, a short tail is hypothesized to have evolved twice, exhibiting homoplasy. A short tail here is a derived trait for the seals, but it is also a shared derived trait for bears, sea lions, and walrus. However, there are a few separate divergences between seals and this group, and the common ancestor is hypothesized to have an elongated tail. In phylogeny C, a short tail is hypothesized to have evolved twice as well, but then was lost in one lineage branch. A short tail is a derived trait for the bears, but it also initially evolved as a shared derived trait for taxa of sea lions, walrus, seals, civets, hyenas, and cats. Cats, hyenas, and civets then lost this short tail, demonstrating an evolutionary reversal. In phylogeny D, a short tail evolved once in the lineage to include the monophyletic group branching from seals to dogs, but it was lost later in the taxa of otters, raccoons, and dogs, exhibiting another evolutionary reversal. Based on this trait and the parsimony principle, phylogeny A is the most likely evolutionary hypothesis as the tail trait only evolved once in the lineage and was not subsequently lost. The parsimony principle guides us to the evolutionary tree with the fewest character-state changes, which is usually regarded as the best.

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Comments

You mention in parentheses at the start of the paragraph that different tail types are scored differently, but it doesn't come up again/isn't explained anywhere else in the paragraph. I assume this is because this is part of a longer piece of writing, but if not, I think it would be helpful to clarify what the significance of the scores is.  

Although this paragraph is long, I feel it is very easy to read and very well organized. I like how there aren't a lot of filler words and intrusions in sentences with random tid bits of information that have no point and ultimately confuse and take up space. The "space" is well used here.