Five questions.
- What makes a fish a fish?
- What makes a continent a continent?
- What makes a country a country?
- What makes a vegetable a vegetable?
- What makes a sport a sport?
What makes a fish a fish?
-
Historically animal phyla (mammals, reptiles, birds, etc.) were
defined by convention and common traits.
-
Biologists later started classifying animals by common ancestry.
-
Animals we call "fish" are very far apart evolutionarily.
-
A common ancestor would also include all mammals.
That's a problem.
Let's ask Wikipedia.
A fish is an
aquatic,
anamniotic,
gill-bearing
vertebrate
animal
with a tough cranium to protect the brain
, but
lacking limbs with digits
.
Included by the definition
Excluded by the definition
