There are 2 modes of reproduction, they include sexual and asexual reproduction. In the asexual mode of reproduction. the offsprings are exact copies of their parents. This is because they have genetic material as that of parents. Thus, there is no process of meiosis, gametogenesis, fertilization and so on. So, there are no variations induced in them and they cannot evolve according to their environment. But in the sexual mode of reproduction, there are 2 parents involved in the process of fertilization. So, offsprings have genetic material from both the parents. They undergo the process of crossing over and variations are introduced in them. So, they can adapt to their environment and evolution takes place. As a result, there are better chances of survival as they have the capacity to adapt themselves to their surroundings.