Well, science says "We don't know yet". Here is my answer:
20 And God said, Let the waters bring forth abundantly the moving creature that hath life, and fowl that may fly above the earth in the open firmament of heaven.
21 And God created great whales, and every living creature that moveth, which the waters brought forth abundantly, after their kind, and every winged fowl after his kind: and God saw that it was good.
22 And God blessed them, saying, Be fruitful, and multiply, and fill the waters in the seas, and let fowl multiply in the earth.
23 And the evening and the morning were the fifth day.
A dog is a Canis lupus familiaris. A wolf is a Canis lupus. That is your scientists classification of those animals. So there you have it.
But according to you everything is in a nested hierarchy and shares a common ancestry so it really doesn't matter if we can tell them apart or not.
Personally I would go with the bible and say that fish are one kind of animal, cattle are another, dinosaurs are another, humans are another, birds are another, insects are another, etc. Which exhibited some speciation along the way.