They use a internal pouch which is named swim bladder.
Explanation; Oxygen will enter a fish’s mouth, and passes through their gills. The oxygen will be taken and gets carried by hemoglobin through their bloodstream. Hemoglobin will take out some of the oxygen into their swim bladder. The amount of oxygen will show if they will sink or rise. Your question is how do they rise. If he goes up too much, the meaning of this is when the gas diffuses into their blood and out the gills.
Got this from a writing, but rephrased it.
Answer: Below
Explanation:
Alligators play an important role in maintaining ecosystem balance. Sitting at the top of the food chain, alligators are top predators and help keep other animal populations in balance. By digging holes and leaving trails throughout marshes, they create habitats for fish and marine invertebrates
The answer would be 1. original-tissue fossils and 2. many species were wiped out
