So, continuing on main vein of this thread, and going from post #287. Note that post #351 was summary of most recent section and post #352 is latest table of contents for this thread.
In this
material, we are still in section 2 of 7, titled "Patterns."
And in this post, I'm starting with new subsection titled, "Classification." This area appears to have 5 to 6 pages in all.
Using the Tree for Classification
Biologists use phylogenetic trees for many purposes, including:
- Testing hypotheses about evolution
- Learning about the characteristics of extinct species and ancestral lineages
- Classifying organisms
All good in my book.
Using phylogenies as a basis for classification is a relatively new development in biology.
Most of us are accustomed to the Linnaean system of classification that assigns every organism a kingdom, phylum, class, order, family, genus, and species, which, among other possibilities, has the handy mnemonic King Philip Came Over For Good Soup. This system was created long before scientists understood that organisms evolved. Because the Linnaean system is not based on evolution, most biologists are switching to a classification system that reflects the organisms' evolutionary history.
It's nice that King Philip did that.
I'm not sure how aware I was of the 2 classification systems. I believe I had heard of both before reading this material, but must admit this feels like type of learning that helps confirm something semi significant in this process (I'm going through).
I'd like to note that the material does provide definition here for "
species" which I find somewhat pertinent, but unless someone (reading this) wishes for me to present that for deeper understanding, I just assume move on. My basic understanding of 'species' is a population that can interbreed and, so far, my guiding understanding is that the species concept is a bit fuzzy.
Evolution is also defined in this portion, which is the topic and is not definition that I'll (ever) let go not noted. The reader can assume I'll be providing summary of this material that will be sure to discuss my understanding of that definition (in this material).
This phylogenetic classification system names only cladesgroups of organisms that are all descended from a common ancestor. As an example, we can look more closely at reptiles and birds.
(Material provides 4 diagrams, all essentially the same, helping with understanding how things are mapped.)
Under a system of phylogenetic classification, we could name any clade on this tree. For example, the Testudines, Squamata, Archosauria, and Crocodylomorpha all form clades.
I understand, I think, the mapping being done. Not sure I understand/agree with qualitative analysis, but pretty sure that I'm not suppose to be analyzing in that way at this time. So moving on.
However, the reptiles do not form a clade, as shown in the cladogram. That means that either reptile is not a valid phylogenetic grouping or we have to start thinking of birds as reptiles.
Again, for overview purposes (understanding mapping in general terms only), I get what this is saying. Beyond that, with further analysis (what I'm reading into the assertions), I find it questionable, but feels like this is not time for that.
Another cool thing about phylogenetic classification is that it means that dinosaurs are not entirely extinct. Birds are, in fact, dinosaurs (part of the clade Dinosauria). Its pretty neat to think that you could learn something about T. rex by studying birds!
Not so 'neat' to me right now, as this is the sort of 'reading into to it' that I had refrained from above. In very general terms, my analysis amounts to seeing the model suggest something that I so far don't have basis for agreeing with in terms of matching 'nature as I observe it' and am more or less having to put faith in these diagrams, which just seem suspect to me.
But I really don't feel (still) that this is time (yet) for that sort of analysis and will hope this subsection is just mainly for purposes of building understanding of 'how things are modeled in evolutionary theory.' If anyone reading this feels there is more to this particular page, and thinks I must stop to discuss it, I feel very open to that. Assuming no one does have that inkling, I'll plan to move on.
In my next post.
Which will be in the sub-page of this subsection on Classification.
(As is ongoing tradition in this thread, I note) Again, in this portion that I covered, the word "observe" or "observation" does not appear.
Next up for this material is still in "Patterns" and is sub-page titled, "Switching to Phylogenetics," which I'll get to in next post.
