If the oceans of the earth got warmer from global warming, would the water of the oceans become more or less salty? what do you think the effect of this change in the ocean salinity (saltiness) would be on the plants and animals that live in the ocean?

I have two different answers. One is what the shcool most likely wants you to think and the other is the truth. 

School: The waters could become more or less salty. Warm water is less dense than cold water so it will sit on top of cold water. It would very bad for plants because not all plants can live in such saltiness conditions. 

Global Warming isn't a thing. It's fake, scientist have lied about it, and it's entirely false. The salt from the ocean comes from the constant bashing of ocean waves on the rocks. "Warm water is less dense than cold water so it will sit on top of cold water." is true, but that doesn't mean the oceans will be more salty if it is warmer, that just says how dense the salt and water is. it can be warmer or colder doesn't matter. 

Hope it helps please let me know.