Explain how systematists commonly identify ancestral and derived character states in the absence of fossil evidence
What will be an ideal response?
ANSWER: In the absence of evidence from fossils, systematists frequently use a technique called outgroup comparison to identify ancestral and derived character states. Using this approach, systematists compare characters in the ingroup, the clade under study, to those in an outgroup, one or a few species that are related to the clade but not included within it. Character states observed in the outgroup are considered ancestral, and those observed only in the ingroup are considered derived. And because the outgroup and the ingroup are phylogenetically related, outgroup comparison allows researchers to hypothesize the root of the phylogenetic tree.
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