The original source of new alleles, upon which selection operates, is mutation, a random event that occurs without regard to selectional value in the organism. Although many model organisms have been used to study mutational events in populations, some investigators have developed abiotic molecular models. Soll et al. (2006. Genetics 175: 267-275) examined one such model to study the relationship between both deleterious and advantageous mutations and population size in a ligase molecule composed of RNA (a ribozyme). Soll found that the smaller the population of molecules, the more likely it was that not only deleterious mutations but also advantageous mutations would disappear. Why would population size influence the survival of both types of mutations (deleterious and advantageous) in populations

Sampling error may allow fixation of one form and the elimination of others in a small population.

Explanation:

It can be seen that in case of a small population size, there are high chances of the elimination or the fixation of the allele in the population when compared to the large population size. Also sampling errors are found in case of small population size that leads to the enhancement of the chances for fixation and also for the elimination of the allele. This large size population doe not have much effect. The random fixation of the either selective allele or the elimination of the disadvantageous allele occurs due to the genetic drift.

SO in order for the population size influenced the survival of both types of mutations , the sampling error may be allowed for the fixation of one of the form and the elimination of the other forms in the small population size.

there are so many examples for that in different areas, like biology experiment carried out in our lab recently.

here's one link:

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.