Unformatted text preview: roup includes
an ancestral species
and SOME but not all of its descendants
Is this also a
Try the “snip test” http://upload.wikimedia.org/wikipedia/commons/thumb/d/dc/Paraphyletic.svg/500px-Paraphyletic.svg.png
See Figure 26.10 (Campbell et al 9th ed) 39
39 A Polyphyletic Group includes some
members with different ancestors 3-chambered
heart • Earlier taxonomy considered birds to be more closely related to mammals than lizards
since both have 4-chambered hearts.
• But, current understanding shows differently.
• Thus a group made of birds & mammals is a polyphyletic
since their MRCA did not have a 4-chambered heart.
(i.e. a similar trait among members was derived from different ancestors)
See Figure 26.10 (Campbell et al 9th ed) 43
43 How many monophyletic groups are there? 46
Why might it be useful to
recognize some nonmonophyletic groups?
• Group together organisms
that share key structural
or ecological traits
• Lack specialized
in plants 47
47 “Algae” is a polyphyletic group
based on nutrition, not relationships 48
48 Shared Characters are used
to construct phylogenetic trees
lizards don’t •Morphological Data
birds crocodiles lizards 50
50 Molecular Data
Ancestral DNA identical
(homologous) at beginning of
split between 2 populations Insertions & deletions
as 2 populations diverge to
new species Figure 26.8 Campbell...
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