The Tangled Bank (Bell, 1982) One theory advanced to explain the success of sexual reproduction has been called "The Tangled Bank" by Graham Bell. This phrase is inspired by the Origin of Species (Bell, 1982). In this theory, it is proposed that sexually reproducing species have an advantage over asexual individuals in the amount of offspring they can produce in a particular environment. In an environment which encompasses various ecological "niches" (Bell, 1982), a single asexual individual will be able to clone itself and fill whichever niches it is suited to fill. Depending upon its source of nutrients, or how well it can survive in a particular climate, it will be able to produce a certain number of clones, to fill the "carrying capacity" of the environment (Bell, 1982). By adding more clones, and thus a more diverse population, more niches within a particular environment can be filled. The carrying capacity of the environment will increase with the variety of asexual individuals, until every niche has been filled. Past this point, any more clones will either need to replace one of the already existing types, or die out. It is obvious though, that a larger variety of asexual individuals means a larger total population, as more of the resources in the environment can be used with an increase in variety. For example, some individuals will prefer one type of food, and others will prefer something different, enabling both to occupy the same area. Bell argues however that within another, similarly diverse environment, A sexual population will also do well. Given the nature of a sexual population, the species will have a certain range of phenotypes and thus needs within its members (Bell, 1982). As in the case with an asexual population, each type of individual will be able to fill the niche that it is suited to. A sexual population with a reasonable amount of genetic differences among its members is somewhat like an asexual population with many different genotypes. Still, to see whether sexual is really better than asexual, you must look at the situation where there are both types of organisms present. In an environment with different niches, where a variety of organism types will be able to reach a greater population, sexual species have the advantage.Whether the population starts out primarily asexual or sexual, the sexual individuals will be able to fill the environment more effectively, and the asexual and sexual species will eventually reach equilibrium (Bell, 1982).