Lecture 6 - Phylogenetics and Systematics How to read...

Info icon This preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
1 Phylogenetics and Systematics How to read phylogenetic trees Classification (Systematics) Types of phylogenetic trees How to make phylogenetic trees How to use phylogenetic trees The fossil record provides information about the history and relationships among organisms 100 million year old dragonfly fossil The fossil record Is based on the sequence in which fossils have accumulated in such strata Fossils reveal Ancestral characteristics that may have been lost over time Fossils dates Provide minimum estimates of the age of a taxon But the history of organisms is also written in their features, and in their genes. Biologists use morphological, biochemical, and molecular comparisons to infer evolutionary relationships. Molecular (sequence) data are now the dominant data source. This is a cladogram. One type of phylogenetic tree. Are you more closely related to a fungus or a plant? Is a tulip more closely related to a mushroom or a human?
Image of page 1

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

View Full Document Right Arrow Icon
2 How to read a phylogenetic tree Morphological and Molecular Homologies In general, organisms that share very similar morphologies or similar DNA sequences are likely to be more closely related. Homology vs. Analogy A potential source of error in reconstructing relationships is similarity due to convergent evolution, called analogy, rather than shared ancestry. Homologous features held in common by a group due to shared ancestry Analogous features are due to convergent evolution Convergent evolution occurs when similar environmental pressures and natural selection produce similar (analogous) adaptations in organisms from different evolutionary lineages Marsupial mole Mole (placental) (The two animals above are exactly as closely related to one another as the two animals below) Human Kangaroo These wings are analagous Bat Bird Each bone is homologous
Image of page 2
3 To determine whether a character state is homologous or analagous – One needs to look at many characters Lizard Four-chambered heart Bird Mammal Lizard Four-chambered heart Bird Mammal Four-chambered heart (a) Mammal-bird clade (b) Lizard-bird clade Analogous (convergent) structures or molecular sequences that evolved independently – Are also called homoplasies Molecular Homologies Systematists use computer programs and mathematical tools to align comparable DNA segments from different organisms Deletion Insertion Here are two unrelated DNA sequences They happen to share 25% of their sites Computer programs are used to separate these chance homoplasies, from similarities that imply relationships A C G G A T A G T C C A C T A G G C A C T A T C A C C G A C A G G T C T T T G A C T A G Figure 26.9 Phylogenetic systematics connects classification with evolutionary history • Taxonomy – Is the ordered division of organisms into categories based on a set of characteristics used to assess similarities and differences Binomial Nomenclature Binomial nomenclature
Image of page 3

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

View Full Document Right Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern