In which atmospheric layer does most of the greenhouse effect occur answer?

Troposphere

Explanation:

The troposphere is the layer of atmosphere that contain four major greenhouse gases and therefore, is the site for the greenhouse effect. The greenhouse gases present in the lower troposphere are water vapor, carbon dioxide, methane, and nitrous oxide.  

These greenhouse gases trap the radiations reflected back by earth's surface during the night. These trapped radiations serve to increase the earth's atmosphere.  

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.