Final answer:
The primary evidence supporting life changes over millions of years includes fossils which show a progression of evolutionary changes, construction of a detailed fossil record, and morphological similarities among different species. These indicate a common ancestry and provide compelling evidence of evolution.
Step-by-step explanation:
We have several forms of evidence that demonstrate life has changed over the course of millions of years. One of the most significant sources of this evidence is fossils. Fossils provide solid evidence that organisms from the past are not the same as those found today. They show a progression of evolutionary changes over time, with scientists being able to determine the age of fossils and categorize them. This categorization helps to construct a fossil record that narrates the history of life and depicts the evolution of form over millions of years. For instance, the fossil record includes highly detailed information showing the evolution of species such as humans and horses. Additionally, the similarities in morphology of appendages among different species like whales, birds, and mammals suggest a common ancestor, further supporting the evidence of evolution through fossils.
Moreover, beyond fossils, evolutionary changes can also be observed in modern species, providing evidence that evolution is an ongoing process. This includes physical changes that occur over extensive amounts of time, shaped by the mechanism of natural selection, which works on individual organisms but can eventually impact the genotype of an entire species over thousands to millions of years.