ABSTRACT
The fitness of an individual will be high if that individual gives rise to many offspring which themselves are reproductively successful. Fitness will not necessarily be maximized by producing the most offspring – it may be better to produce fewer, larger offspring which will have better survivorship. An individual’s contribution to future generations may also be influenced by nongenetic factors. Environmental differences between individuals will influence fitness. Adaptation is the result of natural selection acting on heritable differences in fitness. The genotype is the genetic composition of an individual. In sexual outcrossing species, usually most individuals have differing genotypes. The phenotype is the individual organism, a product of the interaction between its genotype and its environment. A resource is anything which an organism depletes. Environmental conditions are constantly changing. To maintain a relatively constant internal environment in the presence of very variable external conditions requires homeostasis.
