Over time, the population will gradually become more and more suited to its environment as helpful mutations arise and spread through the population, while deleterious ones are weeded out. Ultimately, this process produces organisms that are well adapted to their habitats and way of life.
SWITCH-A-ROO: Ah, here is the old switcharoo again. Give an accurate definition of natural selection - but then mix in fantasy. I do hope he gives some examples of helpful mutations that increase the information in the genome that lead to new kinds of features and an overall improvement in the creature. See how well the famed Richard Dawkins addressed that question here:
https://www.youtube.com/watch?v=zaKryi3605g&t=23s
