The main difference is that quotas restrict quantity while tariff works through prices
Natural selection is the process by which individuals who are best suited to the environment tend to leave (on average) more offspring than others.
Evolutionary changes take place over many generations and through millions of years of natural selection. For the genes to survive, they must be among the strongest.
A verticle group (up and down) is called a GROUP. The horizontal groups (left to right) are called PERIODS
