In evolutionary taxonomy, reptiles are gathered together under the classReptilia (/rɛpˈtɪliə/rep-TIL-ee-ə), which corresponds to common usage. Modern cladistic taxonomyregards that group as paraphyletic, since genetic and paleontological evidence has determined that crocodilians are more closely related to birds (class Aves), members of Dinosauria, than to other living reptiles, and thus birds are nested among reptiles from a phylogenetic perspective. Many cladistic systems therefore redefine Reptilia as a clade (monophyletic group) including birds, though the precise definition of this clade varies between authors.
Any particular words you don’t know? Probably the most likely ones are para- and monophyletic. For a taxon (scientific grouping) to be a valid clade, it needs to be monophyletic, meaning it contains the most recent common ancestor of the group’s other members and all known descendants of that common ancestor. Paraphyletic, by contrast, means not all the descendants are in there. For example, imagine if the mammals just randomly excluded the bears – that would be paraphyletic, because the bears also share a common ancestor with the other mammals.
So a monophyletic group of your family tree might include your grandmother, all her children, and all their children’s children, etc. A paraphyletic one might exclude Gertrude and her kids because she got drunk and stole and wrecked the LeBaron and we fucking know she did it and we don’t talk to her after that.
para- and mono-phyletic were indeed the problem words. I can tell they are related to phylum but “phylum” doesn’t mean much to me except to know that it’s a word for some grouping of species.
The other part where I was snagged is the significance of cladistics and the new/old classification methods. I knew both terms as “words for groups of species and hadn’t dug further.
Between the family tree example and the diagram — got it, thanks to you and your sibling reply.
Reptile Wikipedia:
I kinda know what some of those words mean.
Can I get a picture?
Any particular words you don’t know? Probably the most likely ones are para- and monophyletic. For a taxon (scientific grouping) to be a valid clade, it needs to be monophyletic, meaning it contains the most recent common ancestor of the group’s other members and all known descendants of that common ancestor. Paraphyletic, by contrast, means not all the descendants are in there. For example, imagine if the mammals just randomly excluded the bears – that would be paraphyletic, because the bears also share a common ancestor with the other mammals.
So a monophyletic group of your family tree might include your grandmother, all her children, and all their children’s children, etc. A paraphyletic one might exclude Gertrude and her kids because she got drunk and stole and wrecked the LeBaron and we fucking know she did it and we don’t talk to her after that.
That was a brilliant explanation, thank you.
para- and mono-phyletic were indeed the problem words. I can tell they are related to phylum but “phylum” doesn’t mean much to me except to know that it’s a word for some grouping of species.
The other part where I was snagged is the significance of cladistics and the new/old classification methods. I knew both terms as “words for groups of species and hadn’t dug further.
Between the family tree example and the diagram — got it, thanks to you and your sibling reply.