The easiest way to tell the difference is that monkeys have tails and apes don’t. Chimps are definitely apes and I’m not sure what OP is getting at.
What I’m getting at is taxonomy. A valid taxon has to include all descendents of the crown group. That means that for monkeys to constitute a valid taxon, apes must be included. Same reason why birds are technically dinosaurs.
A monophyletic clade must include all descendants. A taxonomic group itself can hold anything.
Viruses can also integrate DNA into cells and it sticks there forever sometimes, thus bypassing the tree entirely (making it a network, i.e. no longer acyclic thus no longer a tree).
There is a lot of weirdness in the world, stranger than people have dreamed.:-P
Fair enough. I just belong to the people who require a valid taxon to be monophyletic. (Btw., “clade” already implies monophyleti…city? Monophyleticness?)
Also, shut up about viruses, they make a mess of everything and are beautifully chaotic and I hate them and I love them. xD
