Phylogeny and Systematics (Part 6) Phylogeny and Systematics (Making “Trees of Life”) AP Biology Ms. Day

Macroevolution studies focus on change that occurs at or above the level of species The origin of taxonomic groups higher than species level How does this occur? Evolution of new traits (novelties) mass extinctions Open adaptive zones (divergent evolution)

Intro to Phylogenetics https://highered.mheducation.com/sites/98340 92339/student_view0/chapter23/animation_- _phylogenetic_trees.html

Phylogeny What is phylogeny? The evolutionary history of a group of organisms Systematics attempts to reconstruct phylogeny, by analyzing evolutionary relatedness Use morphological and biochemical similarities Molecular systematics uses DNA, RNA and proteins to infer evolutionary relatedness. Different tools are used to reconstruct phylogenies called phylogentic trees.

Making Evolutionary “Trees”: Illustrating Phylogeny  2 Methods Cladistics = BRANCHES NOT TIME RELATED sorts primitive and shared derived characteristics based on evolutionary relationships Makes cladograms

Let’s review in groups…

Cladograms have clades A clade within a cladogram a group of species that includes an ancestral species and all its descendants Cladistics the study of resemblances among clades

Cladistics Each branch is called a clade https://www.youtube.com/watch?v=46L_2RI1k3k

WHY? WHY?

2. Phenetics = BRANCHES ARE TIME RELATED based on overall similarity (morphology) without regard for evolutionary relationships based on how similar organisms look REMEMER: Organisms can develop similar features through converent evolution **Creates phylograms

Represents the divergence of two species Each branch point Represents the divergence of two species Leopard Domestic cat Common ancestor

“Deeper” branch points Represent progressively greater amounts of divergence; more closely related Leopard Domestic cat Common ancestor Wolf

length of a branch reflects # of genetic changes that have taken place in a particular DNA sequence in that lineage More changes here

Currently, scientists use Morphological (anatomy), biochemical, and molecular comparisons to show evolutionary relationships in “trees” Obtained through fossil studies, DNA technology and current organisms

Molecular systematics

Not all Similarities Represent Common Ancestry Homologous structures indicate shared common ancestry Homologous structures are therefore evidence of divergent evolution Analogous structures are similar in function but not in evolutionary history Analogous structures are evidence of convergent evolution It is not always easy to sort homologous from analogous structures

Analogous Structures

How to Make a Trees: Hypotheses

A shared primitive character https://ccl.northwestern.edu/simevolution/obonu/cladogra ms/Open-This-File.swf A shared primitive character a homologous structure that is shared by all groups you are trying to define A shared derived character A new evolutionary trait unique to a particular clade(s)/branch

Outgroups vs. Ingroups Outgroup Species or group of species that is closely related to the ingroup Distinguishes between shared primitive and shared derived characteristics Closely related to ingroup Ingroup the various species we are studying

What is the shared primitive characteristic? Notochord A Cladogram What is the shared primitive characteristic? Notochord

http://www.cengage.com/biology/discipline_co ntent/animations/cladogram_construction.html http://www.wwnorton.com/college/biology/evo lution/ch/04/animations.aspx

Which is the most parsimonious tree? Phylograms and cladograms trees are JUST hypotheses Which is the most parsimonious tree? the best hypothesis which requires fewest evolutionary changes Parsimony does not always work, nature does not always take the simplest course