One way species change over time is called convergent evolution. Convergent evolution is when two species, unrelated through one recent ancestor, become more similar. Here are The Convergent Evolution Definition, Causes, and Examples

Chemical reactions in the real world are very easy to find, for example when burning paper. The paper was originally still a white sheet, after being burned using fire, then the paper was burnt. What are Chemical Reactions? Here are The Definition and Characteristics