How does an increased surface area help the small intestines do it’s job

The primary function of both of these sections is to absorb nutrients into the bloodstream. Both the jejunum and the ileum have linings with many folds that increase the surface area of the small intestine for maximized nutrient absorption. The inner surface of the small intestine is not flat, but thrown into circular folds. This not only increases the surface area, but helps regulate the flow of digested food through your intestine.

not necessarily. higher fitness requires the organism to be reproductive successful. for example, an organism at age 10 with 15 offspring is much more fit than an organism at age 15 with only 5 offspring.