[alainx277]

The "motivation" behind growth and reproduction is that lifeforms that reproduce more will dominate, while lifeforms that do not die out. This is called natural selection.

Mutations in DNA can have a positive or negative impact on the ability to reproduce. Because of natural selection, positive mutations tend to be preserved while negative mutations tend to disappear. There is no intent behind this process; it is simply a consequence of how life works.

While we can't yet say for certain how life got started, it is likely that the first "life" was made up of self-replicating RNA. Because this RNA self-replicated and produced imperfect copies, it was already undergoing evolution at that point, where the RNA strands which were better at copying themselves (due to mutations) were more plentiful.