Phylogeny and Systematics Part 6 Phylogeny and Systematics

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

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

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_view 0/chapter 23/animation__phylogenetic_trees. html

Intro to Phylogenetics • https: //highered. mheducation. com/sites/98340 92339/student_view 0/chapter 23/animation__phylogenetic_trees. html

Phylogeny What is phylogeny? • The evolutionary history of a group of organisms •

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 1. Cladistics = BRANCHES NOT TIME RELATED

Making Evolutionary “Trees”: Illustrating Phylogeny 2 Methods 1. Cladistics = BRANCHES NOT TIME RELATED ▫ sorts primitive and shared derived characteristics ▫ based on evolutionary relationships Makes cladograms

Let’s review in groups…

Let’s review in groups…

Cladograms have clades • A clade within a cladogram ▫ a group of species

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/w atch? v=46

Cladistics • Each branch is called a clade https: //www. youtube. com/w atch? v=46 L_2 RI 1 k 3 k

WHY?

WHY?

2. Phenetics = BRANCHES ARE TIME RELATED ▫ based on overall similarity (morphology) without

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

 • Each branch point ▫ Represents the divergence of two species Leopard Domestic

• 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

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

More changes here length of a branch reflects # of genetic changes that have

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

 • Currently, scientists use ▫ Morphological (anatomy), biochemical, and molecular comparisons to show

• 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

Molecular systematics

Not all Similarities Represent Common Ancestry • Homologous structures indicate shared common ancestry ▫

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

Analogous Structures

How to Make a Trees: Hypotheses

How to Make a Trees: Hypotheses

 • https: //ccl. northwestern. edu/simevolution/obonu/cladogra ms/Open-This-File. swf • 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

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

A Cladogram 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.

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

Phylograms and cladograms trees are JUST hypotheses 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