Phylogeny and Phylogeny and CladisticsCladistics

Which similarities are most Which similarities are most important?important?

It’s not always easy to tell!It’s not always easy to tell!

Evolutionary classification – Evolutionary classification – classifying classifying based on phylogeny, not just structural based on phylogeny, not just structural characteristics.characteristics.

Phylogeny –Phylogeny – the study of evolutionary the study of evolutionary relationships among organisms.relationships among organisms.

Classification using CladogramsClassification using Cladograms

Many biologists now use a method called Many biologists now use a method called cladistic analysis.cladistic analysis.

Cladistic analysis identifies and considers only Cladistic analysis identifies and considers only new characteristics that arise as lineages (new new characteristics that arise as lineages (new line of organisms) evolve.line of organisms) evolve.

Characteristics that appear in recent parts of a Characteristics that appear in recent parts of a lineage but not in its older members are called lineage but not in its older members are called derived charactersderived characters..

CladogramCladogram

CladogramCladogram

Check out this cladogram!Check out this cladogram!

Quick Lab p 453Quick Lab p 453

Complete the Quick Lab neatly to be added to your Lab Complete the Quick Lab neatly to be added to your Lab book.book.TitleTitle: How is a Cladogram constructed?: How is a Cladogram constructed?ProcedureProcedure: a) Copy the chart titled “Derived Characters : a) Copy the chart titled “Derived Characters in Organisms”in Organisms” b) Identify the organism that is least closely b) Identify the organism that is least closely related to the others.related to the others. c) Construct a cladogram that includes the c) Construct a cladogram that includes the animals names and the appropriate derived charactersanimals names and the appropriate derived characters Analyze and ConcludeAnalyze and Conclude: Answer the four questions in : Answer the four questions in complete sentencescomplete sentences Put your completed lab in your lab book and drop it in Put your completed lab in your lab book and drop it in the drawer. the drawer.

Let’s make a CladogramLet’s make a Cladogram

Cladogram

Other Characteristics used to Other Characteristics used to indicate Evolutionary connectionindicate Evolutionary connection Similarities in DNASimilarities in DNA can be used to help determine can be used to help determine

classification and evolutionary relationships.classification and evolutionary relationships. The more similar the DNA of two species, the The more similar the DNA of two species, the

more recently they shared a common ancestor, more recently they shared a common ancestor, and the more closely they are related in and the more closely they are related in evolutionary terms.evolutionary terms.

The more two species have diverged from each The more two species have diverged from each other, the less similar their DNA will be.other, the less similar their DNA will be.

Read Read DNA Evidence DNA Evidence on p. 454 looking at on p. 454 looking at Figure Figure 18-8.18-8.

Other Characteristics used to Other Characteristics used to indicate Evolutionary connectionindicate Evolutionary connection

Molecular Clocks – Molecular Clocks – monitor “neutral” monitor “neutral” mutations that help estimate the length of mutations that help estimate the length of time two species have been evolving time two species have been evolving independently. independently.

Read Read Molecular ClocksMolecular Clocks on p. 455. on p. 455.

- In your notes, compare Positive, - In your notes, compare Positive, Negative and Neutral mutations. Negative and Neutral mutations.

Molecular ClocksMolecular Clocks

Which species appear to be most closely related?

Where is Species B and C’s most recent ancestor?

Where is Species A and C’s most recent ancestor?

Let’s go back to our earlier animation

Cladogram

Other Characteristics used to Other Characteristics used to indicate Evolutionary connectionindicate Evolutionary connection

Similarities in Embryological DevelopmentSimilarities in Embryological Development

Modern Taxonomist’s CriteriaModern Taxonomist’s CriteriaSimilarities and differences in structureSimilarities and differences in structure Homologous structures – same structure but Homologous structures – same structure but

different functiondifferent function Indicate evolutionary connectionIndicate evolutionary connection

PhylogenyPhylogeny Similarities in DNA/RNASimilarities in DNA/RNA Molecular ClocksMolecular Clocks Similarities in Embryological Similarities in Embryological

developmentdevelopment