Taxonomy isn’t biology, though. It’s a man-made classification system. And at the species level it’s much closer to binary definitions than spectrums. So maybe not the best analogy to make.
As is gender:
A man-made classification system
So I’d say it fits perfectly
But taxonomy aims (even though it sometimes fails) to classify organisms into rigid categories, which is exactly the thing you want to avoid with gender, right?
Just like how we understand that species at a real level are actually a spectrum, we do the same thing with our (self-identified) genders. We feel a certain way about ourselves and find the closest available definition to provide to others. It may not be a 100% exact match to you and you will likely have nuance, but so do species.
It actually is helpful, too because it lets others know how you’d like to be treated in a word.
Until you start to use evolution. What a species is, begins to blur as soon as you try to establish evolutionary lines. When is a whale not a whale but just a water enthusiast mammal? somewhere between 50 and 35 million years ago. Exactly when, it’s anyone’s guess. Taxonomy is indeed part of biology, though.
What a species is, begins to blur as soon as you try to establish evolutionary lines.
It doesn’t because “species” is definied as an animal that can have fertile offspring with other members of it’s species. Looking at evolution doesn’t change that definition, it just shows that it’s not a very good definition on an evolutionary timescale. Our concept of species in taxonomy only makes sense within small timeframes.
When is a whale not a whale but just a water enthusiast mammal?
First we have to establish what you mean by “whale” and translate that to the proper order/clade. Then you look at what was the first described fossile in the group is. And that’s your answer. And yes, that answer will change with new fossil discoveries or reclassifications based on other information happen. But as long as you keep up to date with them, the current way we use taxonomy gives quite binary definitions of the majority of lifeforms.
Taxonomy is indeed part of biology, though.
It sure is. But it’s just an arbitrary classification system within the greater field. It is like an “index”, so you can look up what information belongs to the thing you’re looking at. But it doesn’t actually hold much information about biology of the thing itself.
Species actually don’t have a rigid definition that works across all organisms. The most common definition is the one you gave but sometimes it simply doesn’t work, for example any organism the doesn’t use sexual reproduction doesn’t fit this definition. Clarification of extinct populations would also be an issue. Even considering organisms this is usually used with, there are exceptions. For example; domesticated cattle and American bison, coyotes and wolves, and most cat breeds with various wild species.
But it doesn’t actually hold much information about biology of the thing itself.
What do you mean “biology of the thing itself”? Are you talking about morphology which is a different part of biology. And taxonomic trees are often made based on morphological features so there is a connection.
Taxonomically speaking, the first whale was the last common ancestor of all (modern) whales, whether this was a land dweller or already aquatic isn’t important from a taxonomic point of view
Except you’re still at odds with what a “species” even is because you’ll have a bunch of fossils that exist over several million years as one “species” that definitely looks different at the beginning than it did at the end because evolution is such a gradual process that there never really is a clean break between species.
I’m not quite sure how you got there, but you can check my reply to dustyData in this thread. I think that should clear up your question.