Summary
A group containing an ancestor and all of its descendants, called a clade.
In depth
Test: cut one branch of the tree to isolate the group with the common ancestor and every descendant. Mammals are monophyletic. Monophyly is the goal of cladistic classification.
Monophyly can be tested on a tree. It is the main criterion for valid groups in cladistics.
Example: primates form a clade.
A monophyletic group, or clade, includes a single common ancestor and all of its descendants. It can be cut from a phylogenetic tree with one cut. Monophyly is the standard for valid taxa in modern systematics.
Mammalia, Aves (birds) and Angiospermae are monophyletic. Support comes from synapomorphies (shared derived features) and molecular data. Larger clades contain smaller ones, nested like boxes: Primates within Mammalia within Vertebrata. Nodes represent ancestors, and branch order shows relatedness but not time unless drawn to scale.
Example: the clade containing humans and chimpanzees also includes their common ancestor.
Remember: if a group omits any descendants it is not monophyletic.
Frequently asked questions
What is Monophyletic Groups?
A group containing an ancestor and all of its descendants, called a clade.
Which area of biology covers Monophyletic Groups, and how advanced is it?
Monophyletic Groups is one of the 52 topics in Taxonomy & Biodiversity. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include Phylogenetic Classification, Taxonomic Hierarchy, Shared Derived Characters.
Can you give an example of Monophyletic Groups?
Aves is monophyletic and nested within Dinosauria.
What should I learn before Monophyletic Groups?
Work through the Beginner topics in Taxonomy & Biodiversity first, such as Taxonomy, Binomial Nomenclature, Taxonomic Hierarchy, then return to Monophyletic Groups. Intermediate topics assume the Beginner vocabulary.
What topics are related to Monophyletic Groups?
The closest topics to Monophyletic Groups are Phylogenetic Classification, Taxonomic Hierarchy, Shared Derived Characters, PhyloCode. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Monophyletic Groups?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Monophyletic Groups. To practise the whole of Taxonomy & Biodiversity, use the Taxonomy & Biodiversity quiz.
How is Monophyletic Groups different from Phylogenetic Classification?
Monophyletic Groups: A group containing an ancestor and all of its descendants, called a clade. Phylogenetic Classification: Groups organisms by evolutionary relationships so that taxa reflect common ancestry. Read both side by side and note what each one explains.
How should I study Monophyletic Groups step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Phylogenetic Classification and explain the difference aloud. Finally, take the Taxonomy & Biodiversity quiz and come back to this page for any question you miss.