Which statement describes an effect of Darwin's theory of natural selection?

The statement that organisms best suited for their environment will reproduce encapsulates a fundamental concept of Darwin's theory of natural selection. This theory posits that in any given environment, individuals with traits that provide a survival advantage are more likely to thrive and reproduce. As these organisms pass on their advantageous traits to their offspring, the population gradually shifts to reflect these traits, enhancing the adaptation of the species to its environment over time.

Natural selection emphasizes the role of variation within species, where certain characteristics can give individuals a better chance of survival and successful reproduction. This differential survival and reproduction ultimately shapes the genetic makeup of future generations.

The other statements do not align with the principles of natural selection. For instance, the idea that all organisms have an equal chance of survival overlooks the varying degrees of adaptability among individuals in response to environmental pressures. Additionally, while environmental factors influence traits, they do not solely determine characteristics; genetics play a significant role as well. Lastly, the concept of evolution encompasses changes in both physical and behavioral traits, not limited just to physical attributes.