Answer:
The fossil records.
Step-by-step explanation:
The key observational evidence that supports the idea that life on Earth has evolved through time is the fossil record. The fossil record is the collection of fossils that have been preserved in rock formations around the world, and it provides a detailed record of the history of life on Earth.
The fossil record shows that the forms of life on Earth have changed over time, and that different species have appeared and disappeared in a pattern that is consistent with the principles of evolution. For example, the fossil record shows that early forms of life, such as single-celled organisms, were simple and relatively unspecialized, while more complex and specialized forms, such as dinosaurs and mammals, appeared later in the fossil record.
The fossil record also shows that many species of organisms have evolved over time, changing and adapting to their environments in response to natural selection. This process of evolution is supported by other lines of evidence, such as the study of genetics and the development of new species through artificial selection.
Overall, the fossil record is a key piece of evidence that supports the idea of evolution, and it provides a wealth of information about the history of life on Earth and the processes that have shaped the diversity of life on the planet.