If you were using cladistics to build a phylogenetic tree of cats, which would be the best choice for an outgroup?
a. Kangaroo
b. Leopard
c. Domestic cat
d. Iguana

Verified step by step guidance

1. Understand the concept of an outgroup: In cladistics, an outgroup is a species or group that is closely related to the group of interest (the ingroup) but not part of it. The outgroup serves as a reference point for determining the evolutionary relationships within the ingroup.
2. Identify the ingroup: In this problem, the ingroup consists of cats, which includes species like leopards and domestic cats. These are all members of the Felidae family.
3. Determine the characteristics of the options: Analyze the given options to see which one is least closely related to the ingroup. Kangaroos are marsupials, iguanas are reptiles, and leopards and domestic cats are both felids (members of the cat family).
4. Select the most distantly related option: The best outgroup is the one that is not part of the ingroup and is evolutionarily distant. Between kangaroo and iguana, consider which one is more distantly related to cats based on their evolutionary lineage.
5. Conclude the choice: Use the principle of evolutionary distance to finalize the outgroup. The outgroup should help clarify the evolutionary relationships within the ingroup by providing a point of comparison.

Key Concepts

Cladistics

Cladistics is a method of classifying organisms based on shared derived characteristics, which are traits that are present in an organism but absent in its ancestors. This approach emphasizes the evolutionary relationships between species, allowing scientists to construct phylogenetic trees that depict these relationships. In cladistics, the goal is to group organisms into clades, which are branches that include a common ancestor and all its descendants.

Outgroup

An outgroup is a species or group of species that is closely related to the group being studied (the ingroup) but is not part of it. In phylogenetic analysis, the outgroup serves as a reference point to help determine the evolutionary relationships and characteristics of the ingroup. By comparing the ingroup to the outgroup, researchers can identify which traits are derived and which are ancestral, aiding in the construction of a more accurate phylogenetic tree.

Phylogenetic Tree

A phylogenetic tree is a diagram that represents the evolutionary relationships among various biological species based on their genetic or physical characteristics. The branches of the tree illustrate how species diverged from common ancestors over time. Understanding the structure of a phylogenetic tree is crucial for interpreting evolutionary history, as it provides insights into how different species are related and the timeline of their divergence.