Here's why:
* Body plan and functions: These refer to the fundamental structure and how an organism works.
* Through generations: Evolutionary changes occur over many generations, not within a single lifetime.
* Change: The key aspect is that these details are *changing*, not staying the same.
Evolution is a gradual process where populations of organisms change over time in response to environmental pressures and natural selection. These changes can be small and subtle, or they can lead to the emergence of entirely new species.
