Biology Scenrio? (like woah!)?

[Selena Vive]

A group of plant seeds were blown onto an island with an environment that was much hotter than the one the seeds came from. In this environment, plants that have thick leaves have a hard time surviving because their leaves hold too much heat. Plants with thin leaves survivie more easily because their leaves hold less heat. Describe a scenario in which this initial population of plants eventually evolves into a new species of plant that has a different type of leaf from the original plant?

Would this scenro have to do with natural selection or gentic drift (I think thats what its called)?
The second poster, I NEVER intended for someone to do my homework. All I wanted to know what does it have to do with! Jeez.