Sure, mutation would be one way.
Animals change and adapt through evolution by natural selection.
Because all animals that exist have formed, and are being formed and re-formed, continuously, primarily by natural selection.
One was Darwin's theory was the process of evolution by natural selection and the second one was Lyell's theory was that animals can adapt and change their traits to fit the environment.
evolution by natural selection
Only natural selection could be the answer here as natural selection is the main driver of adaptive change leading to evolutionary change and speciation in large populations.
natural selection :")
yes they are
Natural selection
Genetic change is necessary for natural selection to take place
Natural selection usually causes a species to change gradually
Natural selection, Evolution, Artificial selection, disasters
Natural selection is only the result of changing environments, mutation and the variation resulting therein. Natural selection is the process of adaptive change and the main mechanism of evolution that leads to speciation. Natural selection is a process as mutation and variation are grist to the mill of natural selection.