1 / 12

Zoology Notes #2

Zoology Notes #2. Interpreting Cladograms Big Idea: Phylogenies Depict ancestor and descendent relationships among organisms based on homology These evolutionary relationships are represented by Diagrams called cladograms (branching diagrams that organize relationships) .

renata
Download Presentation

Zoology Notes #2

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Zoology Notes #2 Interpreting Cladograms Big Idea: PhylogeniesDepict ancestor and descendent relationships among organisms based on homology These evolutionary relationships are represented by Diagrams called cladograms(branching diagrams that organize relationships)

  2. Reading Cladograms Read like a family tree: show patterns of shared ancestry between lineages. • When an ancestral lineage splits: speciation is indicated due to the “arrival” of some new trait. • Each lineage has unique traits to itself alone and traits that are shared with other lineages. each lineage has ancestors that are unique to that lineage and ancestors that are shared with other lineages — common ancestors.

  3. Quick Question #1 What is our definition of a clade? (look back to zoology notes #1 if you cannot remember) • A group that includes a common ancestor and all the descendants (living and extinct) of that ancestor.

  4. Reading Cladogram: Identifying Clades Using a cladogram, it is easy to tell if a group of lineages forms a clade. • Imagine clipping a single branch off the phylogeny • all of the organisms on that pruned branch make up a clade • So everything in the pink circle is a clade (common ancestor and all descendants)

  5. Quick Question #2 • Looking at the image to the right: • Is the green box a clade? • The blue? • The pink? • The orange?

  6. Reading Cladograms: Clades • Clades are nested within one another • they form a nested hierarchy. • A clade may include many thousands of species or just a few.

  7. Interpreting Cladograms it's easy to misinterpret cladograms as implying that some organisms are more "advanced" than others however, cladograms don't imply this at all. when reading a cladogram, it is important to keep three things in mind

  8. (mis)Interpreting Cladograms: One Evolution produces a pattern of relationships among lineages that is tree-like, not ladder-like.

  9. (mis)Interpreting Cladograms: Two Just because we tend to read phylogenies from left to right, there is no correlation with level of "advancement."

  10. (mis)Interpreting Cladograms: Three For any speciation event on a phylogeny, the choice of which lineage goes to the right and which goes to the left is arbitrary. The following phylogenies are equivalent:

  11. Interpreting Phylogenies: Human Example • The points described above cause the most problems when it comes to human evolution. • It is important to remember that: • Humans did not evolve from chimpanzees. Humans and chimpanzees are evolutionary cousins and share a recent common ancestor that was neither chimpanzee nor human. • Humans are not "higher" or "more evolved" than other living lineages. Since our lineages split, humans and chimpanzees have each evolved traits unique to their own lineages.

  12. Quick Question #3 What is this called? What do you think the red lines represent?

More Related