Final answer:
Organisms adapt to their environments through natural selection, a process by which heritable traits that promote survival and reproduction become more common in a population over time. This adaptation leads to increased fitness in the environment and can result in the evolution of new species.
Step-by-step explanation:
Organisms adapt to their environments through natural selection by developing heritable traits that enhance their ability to survive and reproduce. In this process, traits that confer an advantage in a particular environment become more widespread over generations as these traits help organisms to have greater reproductive success. Conversely, detrimental traits tend to decrease in frequency within a population. Adaptations can range from physical characteristics, like the long neck of a giraffe to reach high foliage, to behavioral changes, like bird migration patterns.
Natural selection operates on genetic variation within a population. When environmental changes occur, natural selection acts on these variations, promoting the frequency of beneficial traits. Over time, the natural selection process leads to a population that is better suited, or more 'fit', for its environment. This is how populations evolve and how new species can emerge when these changes accumulate to a significant degree.
One key point to remember is that natural selection is not a deliberate process, but rather the result of individuals with favorable traits surviving at higher rates and reproducing more successfully than those without such traits. As environments change, what is considered favorable can change too, leading to ongoing adaptation and evolution.