Final answer:
Evolution within a population is well-modeled by the process of natural selection, where genetic variation leads to different survival and reproductive success among individuals. The development of antibiotic resistance in bacteria is a prime example of this model in action. Evidence of evolution also includes the observation of vestigial structures and the fossil record.
Step-by-step explanation:
Model Representing Evolution in Populations
A model that represents evolution within a population is the process of natural selection. In this model, various factors contribute to the evolution of a species. Every population exhibits genetic variation among its individuals, and this variation can affect the individuals' chances of survival and reproduction. When a population is challenged, for example, by an antibiotic in the case of bacteria, individuals with drug-resistant alleles are more likely to survive and reproduce. This leads to an increase in frequency of the antibiotic-resistant trait within the population.
Evidence supporting this model includes the development of antibiotic resistance in bacterial populations, an observation so common it can be seen within hospital environments with intense antibiotic usage. Over time, mutations may give rise to new alleles favoring drug resistance, and these alleles can become predominant within the population through the process of natural selection. This phenomenon is also supported by tracking changes in allele frequencies, which show that populations are not in Hardy-Weinberg equilibrium and are therefore evolving.
Other evidences include vestigial structures, which are remnants of ancestral traits, and the fossil record that documents the progressive changes across extinct species to present-day organisms. These indicate the common ancestry of all life and underscore the continuous nature of evolutionary change.