Final answer:
Comparative embryology looks at the embryonic development of different species to infer evolutionary relationships. Gill slits and tails in vertebrate embryos, including humans, which often disappear before birth, serve as two examples of comparative embryology illustrating common ancestry.
Step-by-step explanation:
Comparative embryology is the branch of biology that studies the formation, early growth, and development of different organisms. It provides insights into how species are related to each other by looking at similarities and differences in their embryonic stages. There are several examples that highlight these comparisons:
- All vertebrate embryos, including humans, exhibit gill slits and tails at some stage during their early development. For terrestrial animals, including humans, these structures typically disappear before birth, while in aquatic animals like fish, they remain into adulthood.
- Embryos of great apes, including humans, develop a tail structure that is usually not present in the adult form. This is an example of a structure that appears in the embryonic stage but is lost by the time the organism is born.
These examples demonstrate how embryonic stages can show a common ancestry among different species, even when the adult forms differ significantly. Structures like gill slits and tails that are present in embryos indicate evolutionary relationships and provide evidence for the process of natural selection acting on mutations and developmental pathways.