Describe how the different layers of the Earth vary by density. When did the materials that make the Earth separate out by density?

if the type of the food available changes, then the frequency of beak types will change, because birds with beaks more suited to the available food will be more successful over time.

straight or amphibians are homeothermic to thermal

not only is it colder, it also becomes darker, less salty, and more dense.

your spelling is a little off : ]