Answer: Cactus plants with these traits were better able than other cactus plants to survive and pass these traits on to their offspring.
Explanation:
Deserts have very little moisture so plants and animals that live there have had to develop traits that will help them retain moisture as long as possible.
Some of those are listed above. Cactus plants today have these traits because they were passed onto them by previous cactus plants who developed and had these traits as well.
These aforementioned previous ones were able to survive better than other cactus plants that did not have the traits above. When they reproduced therefore they spread these traits thereby enabling their offspring to survive as opposed to the other cacti which eventually died out as they could not survive.
