How would you differentiate a monophyletic from a polyphyletic and paraphyletic? I know the definition but can someone provide me with an exmaple and an explanation for it so I can understand better? That would be greatly appreciated!
Certainly! Understanding the difference between monophyletic, polyphyletic, and paraphyletic groups can be a bit challenging, but I'll do my best to explain it along with examples.
1. Monophyletic groups: A monophyletic group, also known as a clade, includes an ancestral species and all of its descendants. In other words, all organisms within the group share a common ancestor. To identify a monophyletic group, you need to find a common ancestor and make sure all the descendants are included.
Example: Let's consider the group of mammals. This group is monophyletic because it includes an ancestral species (a common mammalian ancestor) and all its descendant species, such as humans, dogs, and elephants. All mammals share a common evolutionary history, making this group monophyletic.
2. Polyphyletic groups: A polyphyletic group consists of organisms that do not share a common ancestor. These groups are formed by convergent evolution, where unrelated species develop similar traits but don't share a recent common ancestor. Polyphyletic groups undermine the idea of common ancestry because they exclude some of the descendants.
Example: A classic example of a polyphyletic group is "flying animals." It may seem logical to group bats, birds, and insects together because they can all fly. However, bats (mammals), birds (reptiles), and insects (arthropods) evolved flight independently and do not share a common ancestor. Thus, "flying animals" is a polyphyletic group.
3. Paraphyletic groups: A paraphyletic group is formed when a common ancestor and some, but not all, of its descendants are included. Paraphyletic groups tend to exclude certain species that belong to the common ancestry, creating an incomplete representation of evolutionary relationships.
Example: The dinosaurs provide a good example of a paraphyletic group. Dinosaurs include the extinct species like Tyrannosaurus rex and Velociraptors but exclude the birds (which are living descendants of dinosaurs). Since birds evolved from certain dinosaur species, the exclusion of birds from the dinosaur group makes it paraphyletic.
In summary, when considering the evolutionary relationships, it's important to determine if a group includes all descendants of a common ancestor (monophyletic), if it includes species with unrelated ancestors (polyphyletic), or if it excludes certain species from a common ancestor (paraphyletic).