"An organism that is closely related to the group you’re interested in, but not a part of it. A way to establish a basis of comparison for an trait analysis." This is a definition of: a. An ancestor b. A marker c. An outgroup d. A stem group

c. An outgroup

Explanation:

An outgroup is a group organisms that is not part of the group (ingroup) where evolutionary relationship is determined or investigated, but is closely related to the ingroup.

Th outgroup is used to compare the ingroup and gives room to root the phylogenetic tree. It is used as a reference group to determine the evolutionary relationships of an ingroup.

When determining an outgroup it is necessary to understand the evolution of traits in the phylogenetic tree. The outgroup must not be part of the ingroup, but must be closely related enough to the ingroup to enable for comparisons.

For example Angiosperms can be an ingroup, while gymnosperm an outgroup.

The correct answer is c. An outgroup

Explanation:

An outgroup is that taxon or group used in the analysis that is not included in the study group. It is used for comparative purposes. Usually several outgroup are used in the cladistic analysis that consists of the discovery and selection of characters and taxa, the encoding of characters, and determination of cladograms that best explain the distribution of characters over taxa.

The correct answer is C) There is a larger variety of MHC proteins that can be expressed on the cell surfaces of their immune cells, providing a wider opportunity to recognize and attack pathogens.

Explanation: