Fish are a class of aquatic vertebrates. The combination of gills, fins and the fact that they live only in the water make fish different from all other animals.
Constructive plate boundaries
Answer:
The offspring of the P generation is referred to as the first filial generation (F1).
The answer is shallow, warm, continental seas.
The Ordovician-Silurian extinction happened about 450-430 million years ago. Before the extinction, most multicellular organisms lived in the seas. It was a rich life in shallow, warm, and continental seas. The climate was favorable. Reef-forming corals, as well as the first true vertebrates, some fish, appeared. Trilobites and mollusks were diverse and rich. Green algae were common in the seas.