Unit 10: Part 2 Notes/Study Guide

8.3.2  Use scientific evidence and reasoning to create phylogenetic trees showing evolutionary relationships. 

1. What does a node tell us about two species?

A node represents the most recent common ancestor of the two species or groups that branch from it.  It's where the lineage splits into two.

2. What does a common ancestor look like on a phylogenetic tree?

A common ancestor is represented by a node (branching point) on the tree.  In which the organisms branching from that node share evolutionary history.

3. Be able to draw a phylogenetic tree.

4. What is a clade on a phylogenetic tree?

A clade includes a common ancestor and all of its descendants

5. What evidence do scientists use to support evolutionary relationships illustrated on a phylogenetic tree?

• DNA/molecular data: similar sequences suggest closer relationships

• Morphology: shared physical characteristics, especially homologous structures

• Fossil Records: show changes over time and transitional species

• Embryology: similar early development stages

• Biogeography: Location of species gives clues to common ancestry

6.4.1 Describe how biogeography, fossils, homologous / analogous / vestigial structures, and molecular biology supports the idea of evolution.

1. Be able to define each of the words above.

• Biogeography

  • The study of where species live now and where their ancestors lived

    • Example: Darwin’s finches on the Galapagos Islands

      • Shows evolution because related species found in different areas adapted to their environments

• Fossils

  • Preserved remains or traces of ancient organisms

    • Example: Archaeopteryx (a link between dinosaurs and birds)

      • Shows changes over time and transitional forms

• Homologous Structures

  • Body parts that are similar in structure but may have different functions 

    • Example: Human arm, whale flipper, bat wing

      • Shows evolution because it suggests common ancestry due to similar structures

• Analogous Structures

  • Body parts that have similar functions but different structures

    • Example: Bird wing vs. insect wing

      • Result of convergent evolution, not common ancestry

• Vestigial Structures

  • Structures that have lost their original function

    • Example: Human appendix or whale pelvic bones

      • Suggests descent from ancestors where the structure was useful

• Molecular Biology

  • Study of DNA, RNA, and proteins

    • Example: Humans and chimpanzees share about 98% of DNA

      • More similar DNA = closely evolutionary relationships.

2. Be able to give an example and identify each type above if given multiple options to pick from.

3. Be able to describe how each of the above are used to show evolutionary relationships between organisms.

6.4.5 Explain how we date events in Earth’s history (relative dating, radiometric dating)

• Relative Dating

  • Determining the age of fossils or rocks by comparing their placement in layers

    • Example: A fossil in a lower rock layer is older than one above it

      • Limitation: Doesn’t give exact ages

• Radiometric Dating

  • Using the decay of radioactive isotopes to calculate absolute age

    • Example: Carbon-14 dating young fossils; Uranium-238 for older rocks

      • Strength: Provides actual numerical ages