Paraphyletic vs. Polyphyletic: What's the Difference?
Edited by Aimie Carlson || By Harlon Moss || Published on March 4, 2024
Paraphyletic groups include an ancestral species and some, but not all, of its descendants, while polyphyletic groups consist of species from different ancestors without including the common ancestor.
Key Differences
A paraphyletic group in taxonomy is one that includes an ancestral species and some, but not all, descendants of that ancestor. This exclusion of certain descendants results in a group that does not represent a complete branch of the tree of life. In contrast, a polyphyletic group is formed from species belonging to different ancestral lines, often based on similar but independently evolved traits, without including the most recent common ancestor.
Paraphyletic groups are often identified in evolutionary studies when a single evolutionary lineage gives rise to multiple different groups, but not all of these groups are included in the classification. An example is reptiles without birds, as birds are descended from a group traditionally classified as reptiles. Polyphyletic groups, however, are identified by convergent features that have evolved independently in different evolutionary lines, like the development of wings in bats and birds.
The concept of paraphyly is important in understanding evolutionary relationships as it reflects partial evolutionary histories. However, it can be misleading by omitting certain descendants. Polyphyletic groups, while useful in studying convergent evolution, can be misleading for understanding true evolutionary relationships since they do not stem from a common ancestor.
In systematics, paraphyletic groupings are often revised as more genetic and evolutionary information becomes available, aiming to move towards monophyletic groups, which include an ancestor and all its descendants. Polyphyletic groupings, on the other hand, are generally avoided in modern taxonomy because they do not accurately reflect evolutionary histories.
An example of a paraphyletic group is the class of fish, excluding land vertebrates, whereas a polyphyletic group example is ‘flying animals,’ which includes species like birds, bats, and flying insects, which do not share a recent common ancestor but have the convergent trait of flight.
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Comparison Chart
Ancestral Inclusion
Includes an ancestor and some descendants
Consists of species from different ancestors, excluding the common ancestor
Evolutionary Relationship
Partial lineage representation
No direct lineage representation
Example
Reptiles without birds
Flying animals (birds, bats, insects)
Basis of Classification
Based on direct ancestry and exclusion
Based on similar traits evolved independently
Representation in Tree of Life
Incomplete branch
Crosses different branches
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Paraphyletic and Polyphyletic Definitions
Paraphyletic
"They represent incomplete evolutionary lineages."
Amphibians excluding reptiles form a paraphyletic group.
Polyphyletic
"Polyphyletic groups are formed from species with different ancestors, based on convergent features."
‘Flying animals’ is a polyphyletic group including birds and bats.
Paraphyletic
"Paraphyletic groups include an ancestor and some, but not all, of its descendants."
The class Reptilia is paraphyletic if birds are not included.
Polyphyletic
"They do not include the most recent common ancestor."
Marine mammals from different lineages form a polyphyletic group.
Paraphyletic
"These groups show part of a lineage's evolutionary history."
The term 'fish' is often used in a paraphyletic sense.
Polyphyletic
"Polyphyletic classifications are based on similar characteristics, not common ancestry."
Seed plants are polyphyletic due to convergent evolution of seeds.
Paraphyletic
"Paraphyletic classifications often change with new evolutionary evidence."
Initially, gymnosperms were considered paraphyletic until further genetic analysis.
Polyphyletic
"These groups represent convergent evolutionary traits."
The ability to produce silk is a polyphyletic trait in insects and spiders.
Paraphyletic
"Paraphyletic groups are based on shared ancestry but with exclusion."
Non-avian dinosaurs constitute a paraphyletic group.
Polyphyletic
"Polyphyletic groupings often cross several evolutionary lines."
The category of 'warm-blooded animals' is polyphyletic.
Paraphyletic
Of or relating to a group of taxa that includes the common ancestor of all the members but not all descendants of that ancestor.
Polyphyletic
Of or relating to a group of taxa that does not include the common ancestor of all the members.
Paraphyletic
(systematics) Of a defined group of taxa, not including all descendants of the most recent common ancestor of all members.
Polyphyletic
Of or derived from more than one stock or source.
Polyphyletic
(taxonomy) Having multiple ancestral sources; referring to a taxon that does not contain the most recent common ancestor of its members.
Polyphyletic
Pertaining to, or characterized by, descent from more than one root form, or from many different root forms; polygenetic; - opposed to monophyletic.
FAQs
What defines a paraphyletic group?
A group including an ancestor and some of its descendants.
What is a polyphyletic group?
A group composed of species from different ancestors, based on similar traits.
Can paraphyletic groups be misleading?
Yes, by not including all descendants, they can misrepresent evolutionary history.
Provide an example of a polyphyletic group.
Animals capable of flight, like birds and bats.
How does new evolutionary evidence affect paraphyletic groups?
It can lead to reclassification towards monophyletic groups.
Are polyphyletic groups commonly used in modern taxonomy?
No, they are often avoided as they don't accurately reflect evolutionary relationships.
Are 'flying animals' considered polyphyletic?
Yes, as they include species from different evolutionary lineages.
Why are paraphyletic groups important?
They help in understanding partial evolutionary histories.
What leads to the formation of a polyphyletic group?
Convergent evolution, where different species independently develop similar traits.
Give an example of a paraphyletic group.
Reptiles, if birds are excluded.
Can a polyphyletic group become paraphyletic with new findings?
Yes, if the common ancestor is identified, it may become paraphyletic.
Is the term 'fish' paraphyletic?
Yes, when it excludes land vertebrates.
Do polyphyletic groups cross different evolutionary branches?
Yes, they often encompass species from various branches.
How do paraphyletic groups relate to the tree of life?
They represent an incomplete branch of the tree.
Is a group of seed plants polyphyletic?
Yes, due to the independent evolution of seeds in different lineages.
What's the significance of paraphyletic groups in classification?
They highlight evolutionary relationships and gaps in our understanding.
Are polyphyletic groups useful for studying convergent evolution?
Yes, they are important for understanding how similar traits evolve independently.
Why are polyphyletic groups problematic in evolutionary biology?
They do not accurately represent a common evolutionary lineage.
Are dinosaurs a paraphyletic group?
Yes, if birds are not included.
Why is the concept of paraphyly debated?
Due to its incomplete representation of evolutionary relationships.
About Author
Written by
Harlon MossHarlon is a seasoned quality moderator and accomplished content writer for Difference Wiki. An alumnus of the prestigious University of California, he earned his degree in Computer Science. Leveraging his academic background, Harlon brings a meticulous and informed perspective to his work, ensuring content accuracy and excellence.
Edited by
Aimie CarlsonAimie Carlson, holding a master's degree in English literature, is a fervent English language enthusiast. She lends her writing talents to Difference Wiki, a prominent website that specializes in comparisons, offering readers insightful analyses that both captivate and inform.
