Monophyletic, Paraphyletic, and Polyphyletic Groups

In this video, Nikolai introduces the concept of phylogenetic trees and explains how to identify monophyletic clades by circling a common ancestor and all its descendants. He then discusses sister relationships, highlighting the importance of the most recent common ancestor. The video also covers paraphyletic and polyphyletic clades, explaining how they differ from monophyletic clades. Finally, Nikolai addresses how to determine the relatedness of species based on their common ancestors, concluding with a summary of the key points discussed.

What defines a monophyletic clade?

• A group with a single common ancestor and all its descendants.

• A group with no common ancestors.

• A group with multiple common ancestors.

• A group with only one descendant.

What is the key characteristic of a monophyletic group?

• It includes all descendants of a single common ancestor.

• It includes species with multiple ancestors.

• It includes only one descendant.

• It includes species with no common ancestor.

Which of the following is a sister relationship?

• Species G and H with multiple ancestors.

• Species E and F with no common ancestor.

• Species C and D with a recent common ancestor.

• Species A and B with a distant ancestor.

In a phylogenetic tree, what does a sister group represent?

• Two groups with no descendants.

• Two groups with different ancestors.

• Two groups with a shared recent common ancestor.

• Two groups with no common ancestor.

What is a paraphyletic clade?

• A group with all descendants of a common ancestor.

• A group with unrelated species.

• A group with some but not all descendants of a common ancestor.

• A group with no descendants.

What distinguishes a paraphyletic group from a monophyletic group?

• A paraphyletic group includes all descendants.

• A paraphyletic group includes unrelated species.

• A paraphyletic group has no common ancestor.

• A paraphyletic group includes only some descendants.

Which of the following is an example of a polyphyletic clade?

• Species with a single ancestor.

• Species that share a recent common ancestor.

• Species grouped by similar traits but not closely related.

• Species with no common traits.

Why might species be grouped into a polyphyletic clade?

• Because they are the only species in their group.

• Because they have no common traits.

• Because they have similar traits but are not closely related.

• Because they share a recent common ancestor.

How do you determine if species C is more closely related to D or B?

• By identifying the most recent common ancestor.

• By looking at the physical traits of the species.

• By counting the number of species in each group.

• By comparing the number of descendants.

What is the significance of a recent common ancestor in determining relatedness?

• It shows the age of the species.

• It determines the physical traits of the species.

• It indicates the closeness of the relationship between species.

• It shows the number of species in a group.