When an individual of a species can access its resources or escape predation better than another, it has a better chance of surviving and reproducing. This was coined by Darwin as natural selection. Along with mutations, genetic drift, and migration, natural selection is the driving force of evolution. In some cases, however, an organism may appear to have a characteristic that at first glance does not seem advantageous to its fitness. Fitness is the ability of an organism to survive, find a mate, and reproduce. This can often be explained by sexual selection. Sexual selection occurs when a trait increases an organism's ability to obtain or reproduce a mate. Courtship rituals in which males display their characteristics to females are indicative of female choice or intersexual selection. Females of a species choose a mate based on a trait they find attractive. There are also some species in which the male chooses the mate, and it is the female who has to court (Smith and Smith 2012). In some cases, a chosen characteristic has no other advantages for the organism, and may actually hinder it. For example, the peacock has a whimsical tail. This tail is not used for gathering food and can be cumbersome and difficult for the peacock to drag. A peahen will choose a mate with a flashy tail over a smaller one because it shows her that the male has greater fitness. Even with a bulky tail, he managed to escape predators. Furthermore, it takes a lot of energy and resources to maintain this tail, proving that this is a healthy individual with desirable genes. There is also sexual selection in which males compete for access to females, called intrasexual selection. Male competition can be demonstrated by and...... center of the card ......red. Some characters, such as the shape or position of the horns, could also be mapped onto the diagram. Where these characters were mapped on the diagram would show when the trait diverged. Based on the developmental position of the horns, scientists then grouped the species into five general classes. Horns extending from a vertex between the eyes are located on the back of the head. Other dung beetles may have horns in the center of their heads, growing in the region between the eyes. Below this region is a broad plate at the front of the insect's head, called the clypeus. Horns can also grow from here. The last classes of horns grow from the upper part of the chest, called the pronotum. They can exit from the center or sides of the beetle (Emlen et al. 2005B). In some cases, roaches would have horns in multiple locations; these can be seen in Figure 2.