why the invertebrates is not considered a formal taxonomic group of animals, unlike the vertebrates. ?
- cosmoLv 72 months ago
There are lots of ways to not have a spinal cord.
- daniel gLv 72 months ago
Big surprise for you is they are. The largest of phylums with many subphylums..
- The First DragonLv 72 months ago
Because there is such a huge variety of invertebrates that they have to break them up into smaller categories.
- Anonymous2 months ago
Because Vertebrates share a common ancestor within the group known as chordates. Some chordates are not vertebrates so they are invertebrates. To have a taxon that includes all invertebrates, it will include all animals other than vertebrates and it will include some chordates. That means some chordates will be classified in the same taxon as worms, insects, sponges, jellyfish and mollusks even though they are actually more closely related to vertebrates. That sort of classification is not very useful or informative of evolutionary relationships.
Currently the Kingdom Animalia is divided into many Phyla. One of them is Phylum Chordata, and it includes some invertebrates and all vertebrates. There is no Phylum Vertebrata or Phylum Invertebrata. The informal group invertebrates includes all animal phyla plus some species within the Phylum Chordata. Since there is no formal taxon known as Invertebrata, the invertebrates are therefore an informal group.
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Because the only thing they have in common is that they don't have something (backbone) . Jelly fish and ant don't have a backbone, not really a commonality .
- οικοςLv 72 months ago
Vertebrata is just a single subphylum of the phylum Chordata. Invertebrates are spread over so many phyla that calling something an invertebrate gives you little more information than saying it is an animal. The purpose of classification is to convey as much information as compactly as possible.
Because vertebrates have invertebrate ancestors. A clade comprising the invertebrates would also have to include the vertebrates.
...and we already have that. That's "Kingdom Animalia."