Lecture6_slides_7Sept - 1 1 Phylogenetics The science of...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 1 1 Phylogenetics The science of reconstructing trees THINK TREES! E=mc 2 3 Cladistics: Only certain types of homologous characters are useful for inferring trees: Synapomorphies (shared derived characters) 4 Cladistics: Only certain types of homologous characters are useful for inferring trees: Synapomorphies (shared derived characters) 5 How to tell if a character is derived or ancestral? The OUTGROUP COMPARISON out ingroup 6 How to tell if a character is derived or ancestral? The OUTGROUP COMPARISON Choose an OUTGROUP known (on the basis of other evidence) to be OUTSIDE the group of interest Character states present in the outgroup are assumed to be ancestral Character states present only in the ingroup are potentially synapomorphies out ingroup 2 7 8 Determine the phylogenetic relationships among turtles, crocodiles, birds, and lizards. Use amphibians as an outgroup Attention! Do not memorize characters. Understand the principle! 9 Character Birds Crocs Lizards Turtles Frog Feathers + - - - - Amniotic egg + + + + - Parental care + + - - - Four chambered heart + + - - - Outer carapace - - - + - Two skull fenestra + + + - - Absent(-) vs Present(+) To reconstruct a tree we need characters. But not any old character! We need: Homologous characters and synapomorphies ! 10 Character Birds Crocs Lizards Turtles Frog Feathers + - - - - Amniotic egg + + + + - Parental care + + - - - Four chambered heart + + - - - Outer carapace - - - + - Two skull fenestra + + + - - Absent(-) vs Present(+) To reconstruct a tree we need characters. But not any old character! We need: Homologous characters and synapomorphies ! 11 Cladistic estimation of phylogeny (with informative characters shown) Amniotic egg: present Heart chambers: four Parental care: present Skull fenestra: two 12 Cladistic estimation of phylogeny (with informative characters shown) Amniotic egg: present Heart chambers: four Parental care: present feathers carapace Skull fenestra: two 2 7 8 Determine the phylogenetic relationships among turtles, crocodiles, birds, and lizards....
View Full Document

This note was uploaded on 01/01/2012 for the course BIOEE 1780 taught by Professor Harrison during the Fall '10 term at Cornell University (Engineering School).

Page1 / 7

Lecture6_slides_7Sept - 1 1 Phylogenetics The science of...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online