Rocks containing 450-million-year-old ordovician fossils contain jawless fish. younger devonian rocks that are only 400 million years old contain fossils of jawless fish and fish with jaws. this evidence supports the idea that

The correct answer is - the species evolved.

The fact that in one period there's only fish species that are jawless, and after some period there's also fishes that have jaws, and the fishes are obviously connected and share common ancestors, supports the theory of evolution.

Some of the jawless fish species have started to occupy certain niches in the food chain that required them to develop jaws. The evolutionary pressure for the fishes to survive in certain conditions, resulted in the development of jaws, and with the jaws cam the teeth as well. The main purpose of such and evolutionary trait among the fishes has been the occupying of the predatory niche in which the jaws and sharp teeth are advantageous.

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