Discussed changes that occurred between the Ordovician period and the Silurian in terms of climate, habitat variability, the concept of the niche and the competitive exclusion principle. We discussed what animals survived the mass extinction of the Ordovician and radiated in the Silurian. Next we covered similar concepts regarding the Devonian period (AKA the age of fishes). We investigated the continuing rise of cartilaginous fishes and the rise of bony fishes. Explored how the bony fish diversified and what species were left at the end of the Devonian.