What is the Difference Between Ingroup and Outgroup in Biology?
🆚 Go to Comparative Table 🆚In biology, the terms ingroup and outgroup refer to the classification of organisms within a phylogenetic analysis, which is a study of the evolutionary relationships among a set of organisms or groups of organisms called taxa.
- Ingroup: The ingroup is the group of taxa that is investigated for determining evolutionary relationships. These taxa are closely related or sister taxa, and they share a common ancestor. The ingroup is the set of organisms under study, and their evolutionary relationships are analyzed in comparison to the outgroup.
- Outgroup: The outgroup is a more distantly related group of organisms that serves as a reference group when determining the evolutionary relationships of the ingroup. The outgroup is essential for understanding the evolution of traits along a phylogeny, as it allows for the polarity (direction) of character change to be determined. The choice of an outgroup is important, as it should be less closely related to the ingroup than the ingroup is to itself.
In summary, the main difference between ingroup and outgroup in biology is that the ingroup consists of closely related organisms under study, while the outgroup is a more distantly related reference group used to determine the evolutionary relationships of the ingroup.
Comparative Table: Ingroup vs Outgroup in Biology
In biology, the terms "ingroup" and "outgroup" are used to describe the relationships between taxa in the context of determining evolutionary relationships. Here is a table summarizing the differences between ingroup and outgroup:
| Ingroup | Outgroup |
|---|---|
| A group of taxa that are closely related, sharing a common ancestor, and considered to be more closely related to each other than to other taxa | A reference group used to determine evolutionary relationships between taxa in the ingroup, typically less closely related to the taxa in the ingroup than those in the ingroup itself |
| Ingroup taxa are sister groups, meaning they share a common node in the cladogram and are descendants of the same ancestor | Outgroup taxa do not share a common node in the cladogram with the ingroup taxa, and they are not descendants of the same ancestor |
| Ingroup taxa can be used to identify shared derived traits and ancestral traits among the species being studied | Outgroup taxa can provide a better understanding of where the main group of organisms falls within the larger tree of life and is useful when constructing evolutionary trees |
In building a phylogenetic tree, the nested groups are organized based on shared derived traits (traits different from those of the group's ancestor). The outgroup can serve as a proxy for the ancestral species, and its traits may represent the ancestral form of each characteristic.
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