phylum porifera

anonymous asked:

What is the problem with Linnaean classification? And what other system should be used instead?

Linnaean classification is outdated based on our current knowledge of the evolution of life. 

It is a method of classifying organisms based on traits and characteristics of them that we find important; it’s entirely subjective. 

Cladistics is the classification of organisms based on their evolutionary realtionships; which no, we don’t know exactly all the time, but we’re constantly learning more and making our picture of the evolution of life on earth more complete, making cladograms and phylogenetics more and more informative every day. 

For example, birds are in the class “Aves” and the phylum “Chordata.” We arbitrarily decided that birds are different from reptiles (”Reptilia”) because they were warm blooded and had feathers. But dinosaurs, which are in the class Reptilia, are also warm blooded and also have feathers. Also, birds evolved from dinosaurs - so they’re a group of dinosaurs - which means they’re in the class Reptilia and Aves! 

Also, Synapsids are the “ancestors” of mammals. In Linnean classification, they’re put in Reptilia. However, as far as evolution is concerned, they aren’t reptiles

Also, sponges (Phylum “Porifera”) - some of them might be more closely related to more complex animals than others -

Also, almost all protists are more closely related to fungi, animals, or plants than they are to other protists, making the kingdom “Protista” functionally useless. 

ALSO, there is a very good chance that Eukaryotes are a group of Archaeans, making the “domain of life” part of Linnaeus useless and misleading as well.

ALSO, LINNAEAN CLASSIFICATION IMPLIES A HIERARCHY OF LIFE, THAT CERTAIN THINGS ARE MORE COMPLEX OR ADVANCED THAN OTHERS, IT IMPLIES THE “LADDER FORM” OF THINKING OF EVOLUTION, AND THAT EVOLUTION IS WORKING TOWARDS A GOAL, WHICH IT IS NOT

So we use cladistics, which yes, retains main of the same names as Linnean classification, but they aren’t ranked anymore, and they’re defined based on evolution rather than arbitrary traits that we have magically decided are more important than others

For example of how we define groups in cladistics is Dinosauria, which is defined as the most recent common ancestor (MRCA) of Meglosaurus and Iguanodon, and all of that MRCA’s descendants. 

Another example that shows a different way we define groups is Carnosauria. Carnosauria is defined as all Tetanurans that are more closely related to Allosaurus than to modern birds. See how this is based on something that happened in the past rather than something that we just chose?

Yeah, parts of it are arbitrary - we don’t define every cladistic grade, but that’s because it would be impossible to do so! We name the groups that are really important, and the ones that aren’t we just show using cladograms. 

For an example for how you’d list that out, let’s take the house sparrow. Yes, this is going to be a long list. Yes I’m retaining the genus/species, mostly because there isn’t anything else to use. I apologize for nothing. And you can point out the important groups in a classification list by using, say, bold type, which is what I do.

Cellular Life, Archaea, Proteoarchaeota, Eukaryota, Unikonta, Opisthokonta, Holozoa, Filozoa, Metazoa (”Animalia”), Eumetazoa, Planulozoa, Bilatera, Nephrozoa, Deuterostomia, Chordata, Craniata, Vertebrata, Gnathostomata, Eugnathostomata, Teleostomi, Euteleostomi, Sarcopterygii, Rhipidistia, Tetrapodomorpha, Eotetrapodiformes, Elpistostegalia, Stegocephalia, Tetrapoda, Reptiliomorpha, Anthracosauria,  Batrachosauria, Cotylosauria, Amniota, Sauropsida, Eureptilia, Romeriida, Diapsida, Neodiapsida, Sauria, Archosauromorpha, Archelosauria, Crocopoda, Archosauriformes, Eucrocopoda, Archosauria, Avemetatarsalia, Ornithodira, Dinosauromorpha, Dinosauriformes, DinosauriaSaurischia, Eusaurischia, Theropoda, Neotheropoda, Averostra, Tetanurae, Orionides, Avetheropoda, Coelurosauria, Tyrannoraptora, Maniraptoriformes, Maniraptora, Pennaraptora, Paraves, Eumaniraptora, Averaptora, Avialae, Euavialae, Avebrevicauda, Pygostylia, Ornithothoraces, Euornithes, Ornithuromorpha, Ornithurae, Neornithes, Neognathae, Neoaves, Inopinaves, Telluraves, Australaves, Eufalconimorphae, Psittacopassera, Passeriformes, Passeri, Passerida, Passeroidea, Passeridae, Passer domesticus

“ Several levels of hierarchy in the structure of the skeleton of the glass sponge Euplectella (Aizenberg et al. 2005; Weaver et al. in press). (a) whole basket, (b) woven glass fibres, © fibre bundle joined by glass matrix, (d) laminated structure of single glass fibre, (e) protein layer gluing successive glass layers, (f) colloidal structure of glass”

Fratzl, 2007