Posted by I need to vent . . .
I’m sick and tired of people referring to “higher” and “lower” eukaryotes. And, while I’m at it, I’m also sick of people mixing up “homology”, “identity” and “similarity”. This is nothing new; I’ve just reached a point where I need to write it down for the world to see.
First, the ‘higher’ eukaryotes thing. Measured how? Most people mean animals when they talk about ‘higher’ eukaryotes. Some are also referring to plants, I think. But I’m not sure, and that’s the first problem: it’s a meaningless term. Refer to clades and save us all some time and angst. Second, if both plants and animals are ‘higher’ eukaryotes, then it’s a paraphyletic group — they got high separately (see the eukaryote tree here). I guess the dutchie weren’t being passed between the algae and the metazoans.
And, if you study biology, take some time to learn what homology means. Two sequences/structures/whatever are either homologous or they are not. There are no degrees of homology. You can’t measure percent homology. Homology just means they share a common ancestor. If you want to say how divergent they’ve become since their common ancestor, then tell me what their percent identity is (if it’s a DNA sequence). If you want to make a comparison based on function or some higher order analysis beyond simple sequence comparison, then you can refer to their similarity. But don’t say that two sequences have low homology or high homology because you sound like a retard.
I have taken to asking stupid questions to people that misuse these terms. You could be next on the list, and you don’t want that. Or do you?
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