Natural selection allows nature to chose which species survives. Only the fittest get to pass on their genes. And by fittest i mean the ones that are better adapted to the environment.<span />
I believe it is 'white fur' because living in the Tundra means it is snowing. Snow is white, so basically, the white fur is specifically for the Tundra.
I hope it helps.
This part of the enzyme is known as the active site. Enzymes are organic molecules that catalyze certain chemical reactions in the body. A catalyst is any chemical that speeds up another reaction without being used up in the reaction itself. This means that at the end of the reaction the enzyme is able to operate on other molecules in another reaction.
This sums up most of them