If it walks like a duck and talks like it a duck....it may, in fact, be a bikini model... Okay, likely not. But we do sometimes group insects, animals and plants together because of superficial characteristics. No offense to bikini models here, I know you take your profession quite seriously and suggesting you walk like ducks in high heels might be misinterpreted as mean.
Mean, mean convergent biologists.
There are times when we classify animals together because of superficial characteristics and actually nail it. On those lucky occasions, the DNA supports our claim. Just as often as not, the "family" resemblance stops there. So what is going on?
It may be the trickery of convergent evolution.
What you see is not necessarily what you get. Nature doesn't like brand name. So, how does it all work? We can start with convergent evolution. It is the process by which two or more independent lines of evolutionary development bring about superficially similar end-points.
Think about a gastropods (snails) and ammonites. Both can have lovely coiled shells, but ammonites are more closely related to their squid cousins than the shells beneath our feet. When different groups of organisms are subjected to the same selection pressure hey tend to evolve a simlar design feature.
Picture a shark and dolphin or a large marine reptile from Cretaceous seas - their streamlined bodies provide excellent energy-effiicency under water, each looking like svelt cousins of the sea but unrelated on the ancestral tree.
