The Difference between Natural Selection and Sexual Selection
There are debates raging on whether to regard natural selection and sexual selection separately. On one hand is the argument that the two are mutual and in particular, that sexual selection is a part of the natural selection. On the other hand is the contention that the two are exclusive of each other because the manner in with each selection progresses (Andersson & Simmons, 2006); (Kokko, Jennions & Brooks, 2006). For instance, natural selection is not selective in the sense of deliberation. Natural selection is eliminative, where organisms that do not meet the reductive nature of their environments cease existing. The elimination has no ordered sequence because it not definitive which organisms are up for elimination. Additionally, mate choice occurs in both males and females, although females appear to exercise this choice more than males (Rundle, Chenoweth & Blows, 2006). Alternately, sexual selection is deliberative because it involves organisms exercising elements of premeditation and choice, elements absent in natural selection.
There are several characteristics that make up an organism that predispose some organisms do perform better compared to others in environments exigent for their existence. However, determining the interaction of these challenges with their environment is not straightforward. To illustrate, showing how mating preferences evolve genetically is challenging and compounded by the fact that several mechanisms co-occur (Andersson & Simmons, 2006). Such dynamics are a filter that disrupts the eliminative tendencies of natural order. This gives rise adaptations of organisms in a process that sees sexual selection complementing while at the same time disrupting natural selection (Rundle, Chenoweth & Blows, 2006). Complementarily arises from the fact that only those organisms that survive the natural selection can be able to reproduce, but not all of them are able to do so due to the filters of sexual selection. A major advance in sexual selection is that it can continue after copulation, with implications especially when taken from the female organism perspective (Andersson & Simmons, 2006).
The filters in this regard refer to one organism making certain choices that are a limiting factor in the sexual selection. I have in mind female behavior with regard to preferring investment in their offspring. Observations show that male choice by females is the first step in the process of paternity choice (Andersson & Simmons, 2006). This leads to a situation where males have to compete not only with the offspring, but also with themselves. The outcome is males tending to form behaviors that females find attractive. These behavioral modifications are the filters that tend to check the eliminative momentum of natural selection given the criteria they employ differs from that of natural selection. If an attractive male trait is to manifest to some extent in females with the attendant ramifications, there exists the potential for intra-organism conflict (Andersson & Simmons, 2006). However, there are instances where sexual and natural selections mutually promote the competitive elimination common in natural selection (Rundle, Chenoweth & Blows, 2006). This is manifest where the stronger males tend to overpower weaker ones and win the favor of the females.
Admittedly, whereas females are easily the limiting factor in sexual selection, this function is not exclusive to them. Scholars observe that females demonstrate a preference for males possessing resistance genes whose combination with the former result in among other things, best immune responses (Kokko, Jennions & Brooks, 2006). Other factors such as cost of mate choice and biological adaption of organisms account contribute to the liming role in sexual selection, though these factors could use more investigation (Andersson & Simmons, 2006). For example, the prevailing assumption was that natural selection it was that resulted in organisms better adapted to their environments vis-à-vis their predecessors. Nevertheless, this is not the case given that a close examination of that assumption indicates that possibilities for adaptive anomalies arise. Conflicts between the sexes can further selection pressures on preference and the preferred trait (Andersson & Simmons, 2006).
Consider the male ornaments. Studies show that females prefer male ornaments (Andersson & Simmons, 2006). It follows that if the assumption that natural selection resulted in better adaption for the organisms, then the males would have developed abnormal ornamentation. The result would be that these ornaments would, because of their superfluity, cease being useful with regard to their functional purpose (Andersson & Simmons, 2006). The outcome would be many males dying off because of the maladaptive superfluity of their ornaments that have ceased being useful (Rundle, Chenoweth & Blows, 2006).
This is useful to note because the reproductive success of males is contingent on among other things, the number of females they mate with, fertility of these females and the number of each female’s eggs they fertilize (Kokko, Jennions & Brooks, 2006).Unsuccessful males die out in both sexual and natural selections. Evidence of this is scholarship’s attribution of evolutionary traits such as male genital morphology and ejaculate size to male adaptation for influencing female reproductive physiology (Andersson & Simmons, 2006).As a rule, the most assertive males from a natural selection standpoint are potentially more successful sexually although this is not a guarantee given the limits the latter imposes through its filters.
As the foregoing explores, natural and sexual selections though mutual, differ primarily in the way they eliminate organisms and the factors that contribute to the elimination. Whereas they share some denominators such as allowing the surviving organisms to reproduce, natural selection follows more rigid elimination criteria. Sexual selection however comes about because of a combination of several factors that, while fulfilling sexual selection, disrupt natural selection.

References
Andersson, M., & Simmons, L. W. (2006). Sexual seduction and male choice. Trends in Ecology and Evolution 21(6), pp. 296-302.
Kokko, H., Jennions, M. D., & Brooks, R. (2006). Unifying and testing models of sexual selection. Annual Review of Ecological Evolution 37, pp. 43-66.
Rundle, H. D., Chenoweth, S. F., & Blows, M. W. (2006).The roles of natural and sexual selection during adaptation to a novel environment. Evolution 60(11), pp. 2218-2225.