Final answer:
D. Change in populations through time as a response to environmental change. The evolutionary theory proposed by Charles Darwin is change in populations through time as a response to environmental change, which occurs through the process of natural selection, where advantageous traits are passed on to succeeding generations, resulting in evolution.
Step-by-step explanation:
The evolutionary theory proposed by Charles Darwin is D. Change in populations through time as a response to environmental change. In 1859, Darwin published 'On the Origin of Species', detailing his observations and the concept of natural selection. This process explains that within a population, individuals exhibit variation due to mutations in their DNA. Through natural selection, individuals with traits that are better adapted to their environment tend to survive and reproduce at higher rates, passing on their advantageous traits to the next generation. Over time, this can lead to evolution of the population, with new species potentially arising. The ability to adapt in response to environmental pressures ensures the persistence of favorable traits within a population. Natural selection is the mechanism by which evolutionary change is explained, leading to the diversity of life observed on Earth.