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Constructing a Cladogram

Constructing a Cladogram. Review: Cladogram vs. Phylogeny Tree Cladogram Terminology. Cladistics & Phylogeny. Cladograms Illustrate (give us a picture) of the evolutionary relationships ( phylogeny ) of different groups of species of organisms.

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Constructing a Cladogram

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  1. Constructing a Cladogram Review: Cladogram vs. Phylogeny Tree Cladogram Terminology

  2. Cladistics & Phylogeny • Cladograms • Illustrate (give us a picture) of the evolutionary relationships (phylogeny) of different groups of species of organisms. • Allow scientists to infer which groups are more closely related & the general sequence of events that gave rise to each group. •  it focuses on shared, derived (new) trait •  uses branching approach to show relationships among species •  assumes that all species are descended from a common ancestor

  3. Letters A to E at “branching points” represent the most recent common ancestor of groups that arise beyond that point. What else can you interpret from this cladogram?

  4. Phylogenies • Based on careful evaluation of a wide range of evidence • fossil record • morphology (physical characteristics) • genetics (DNA) Cladistics – a method of determining evolutionary relationships based on the presence or absence of recently evolved traits(derived traits). Synapomorphy – a derived trait shared by two or more species or groups (ex. All birds have feathers & are more closely related to each other than reptiles, which do not have feathers).

  5. Cladistics Classification Hypothetical cladogram: 2 1 3 4 5 TIME F E D C Sister group (most closely related group in the cladogram) B Out group (ancestral) A #1 – 5 are different species populations (taxa) that come from an ancestral taxa  when a taxa acquired a derived trait, the original species cease to exist A – F are favourable characters or traits acquired from e.g. random mutations  character A is: symplesiomorphy(shared, ancestral characteristic) because it is shared by/found in all of the resulting 5 taxa  character B is: synapomorphy(derived, ancestral characteristic) because it is shared by/found only in taxa 4 and 5

  6. Cladistics Classification Interpreting cladogram: 1 TIME A After acquired trait A, the ancestral species becomes extinct while a new species population is formed, taxa #1. They survive till modern day & does not change

  7. Cladistics Classification Interpreting cladogram: 1 5 TIME 4 B A After acquired trait A, the ancestral species becomes extinct while a new species population is formed, taxa #1. They survive till modern day & does not change Along the way, an individual from taxa #1 acquires trait B & form taxa #45

  8. Cladistics Classification Interpreting cladogram: 1 3 5 TIME 4 C B A After acquired trait A, the ancestral species becomes extinct while a new species population is formed, taxa #1. They survive till modern day & does not change Along the way, an individual from taxa #1 acquires trait B & form taxa #45 An individual from taxa #1 acquires trait C, populate & form taxa #3

  9. Cladistics Classification Interpreting cladogram: 1 3 4 5 TIME E D C B A After acquired trait A, the ancestral species becomes extinct while a new species population is formed, taxa #1. They survive till modern day & does not change Along the way, an individual from taxa #1 acquires trait B & form taxa #45 An individual from taxa #1 acquires trait C, populate & form taxa #3 Some members from taxa #45 acquire trait D, others trait E dividing this population into two most recent taxa #4 and #5

  10. Cladistics Classification Interpreting cladogram: 2 1 3 4 5 TIME F E D C B A After acquired trait A, the ancestral species becomes extinct while a new species population is formed, taxa #1. They survive till modern day & does not change Along the way, an individual from taxa #1 acquires trait B & form taxa #45 An individual from taxa #1 acquires trait C, populate & form taxa #3 Some members from taxa #45 acquire trait D, others trait E dividing this population into two most recent taxa #4 and #5 An individual from taxa #1 acquires trait F, populate & form taxa #2

  11. How to make a cladogram? http://ccl.northwestern.edu/simevolution/obonu/cladograms/Open-This-File.swf

  12. Constructing Cladograms Tutorial Read through “Sample Problem 1” on page 351 of the Nelson textbook. Take notes on this. Try the practice question on p. 352. The challenge will be in making inferences about the more recently derived trait. Compare your cladogram with another student. Answer question #8 on p. 355. Complete Cladogram Worksheet-posted on My Class Site under “Homework” –evolution-handout folder 6) Darwin's Voyage- Watch YouTube Video-posted on My Class Site under “Lesson”- Evolution-folder

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