Final answer:
The strongest evidence for common ancestry in biology includes homologous and vestigial structures, as well as comparative DNA analysis.
Step-by-step explanation:
The strongest type of evidence to support common ancestry in biology is the presence of homologous structures. These are structures in different organisms that have a similar underlying anatomical structure but may serve different functions. For example, the forelimbs of mammals such as humans, bats, and whales have the same basic bone structure, indicating a common ancestor.
Another strong piece of evidence is the presence of vestigial structures. These are structures that have no apparent function in an organism, but are remnants of functional structures in its ancestors. The appendix in humans, which serves no known purpose, is a vestigial structure that suggests a common ancestor with other mammals.
Comparative DNA analysis is also a powerful tool to support common ancestry. DNA sequences can be compared between different species to determine their level of similarity. The more similar the DNA sequences, the more likely it is that the species share a common ancestor.
Learn more about evidence for common ancestry