Research this Choose any animal or plant. Describe the characteristics of the species, its habitat and its way of life. In what ways does the species appear to be adapted to where and how it lives?
14.3 Natural selection and evolution within a species
Over long periods of time the process of natural selection may cause gradual evolution within a species. For example, scientists think that modern-day horses can run faster than their ancestors. This is because over millions of years the process of natural selection favoured the faster horses in each generation. Faster horses could escape predators more easily than slower ones. Therefore, these horses could live longer and have more offspring than the slow horses. This meant that in the next generation there would be a greater number of horses that could run fast. The species as a whole evolved to become faster because with each new generation there were more and more offspring that inherited their parent’s ability to run fast. For evolution to occur, the characteristics that are favoured by natural selection must be inheritable (genetic).
Fig. 7 The image shows the evolution of the Mongolian wild horse.
Evolution of a new species Sometimes a new species can evolve from an existing one. This often happens when a group becomes separated from the rest of the species. The separated group may begin to evolve in different ways to the rest of the species. This occurs because their new environment is different which means that the characteristics needed for survival are different. Through natural selection over many generations the separated group will acquire these particular characteristics. Eventually, the descendants of the separated group will form a new species, for example penguins, as explained in the following case study.
