Why are fennec foxes different from Arctic foxes and gray foxes?

The difference between the fennec fox and the Arctic fox it that the fennec fox lives in hot conditions, and the arctic fox live in colder conditions. Also, they don't look like each other, the fennec fox has large ears so it can loose heat fast from it giant span, and it is has a much smaller skeleton to the arctic fox. Also, the fennec fox is an gingery colour. The arctic fox has small ears so it doesn't loose as much heat so it can stay warm in it harsh environment, it has white fur, and a much bigger skeleton to the fennec fox.