Why Do Most Placental Mammals Lack a Cloaca?

💡 The Answer

• Most placental mammals have separate orifices for evacuation and reproduction.
• This contrasts with many other vertebrates that have a single opening called a cloaca.
• The cloaca serves digestive, reproductive, and urinary functions.
• Animals with a cloaca include amphibians, reptiles, birds, and cartilaginous fish.
• A few mammals also retain this ancestral trait.