Ch 26 - Phylogeny and the tree of life (1 slide per page)-2

10 campbell et al 9th ed 38 38 a paraphyletic group

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Unformatted text preview: roup includes an ancestral species and SOME but not all of its descendants Is this also a monophyletic group? Try the “snip test” 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 46 Why might it be useful to recognize some nonmonophyletic groups? • Group together organisms that share key structural or ecological traits Example: “Algae” • Photosynthetic • Lack specialized adaptations found in plants 47 47 “Algae” is a polyphyletic group based on nutrition, not relationships 48 48 Shared Characters are used to construct phylogenetic trees Birds & crocodiles have gizzards; lizards don’t •Morphological Data •Molecular Data •Behavioral Croc Bird 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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