Biology by Bradford
7.9.A, 7.9.BA cladogram
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7.9 Phylogeny: revision map
The subtopic in the middle and four tasks round it: label a diagram, complete a table, put a process in order and fill 8 gaps. Every box rests on a learning objective of the topic in the AP Biology course and exam description. Type into the blanks and check them, or print it on A4, Letter or A3 with an answer key.
Phylogeny
AP Biology ยท Unit 7 Natural SelectionHover over a box to see it. Untick it to leave it off this sheet and its printout.
Name7.9.ACladogram vocabulary
| Term | Meaning |
|---|---|
| a branch point: the last common ancestor of the groups beyond it | |
| an ancestor and all its descendants | |
| Outgroup | a taxon known to have branched off earliest, to show which traits are ancestral |
| Shared derived trait | a new feature that appeared in an ancestor and is passed to its descendants |
Topic 7.9Phylogeny
7.9.BBuilding a cladogram from traits
Number the steps in order.
- Make a table of which taxa have which traits.
- The trait shared by the fewest taxa is placed nearest the tip; the more widely shared, nearer the root.
- Check against DNA data, and choose the tree needing the fewest changes: the most parsimonious.
- Traits shared by all taxa are ancestral, and give no branching.
- Choose the taxa and an outgroup.
7.9.BMolecular data
Traits can be misleading, because analogous features arise by convergence. DNA and protein sequences give many more characters, and the number of differences between two species roughly tracks the time since they diverged, which is the idea of a molecular . A phylogenetic tree is a hypothesis, which is revised when new data are found.
Word bank cladeCladeclockderived characteristicnodeNodeoutgrouproot
Answer key
Every box on the sheet with its gaps filled in, as the subtopic reads in full.
LabelA cladogram
- root
- node
- derived characteristic
- clade
- outgroup
TableCladogram vocabulary
Term Meaning Node a branch point: the last common ancestor of the groups beyond it Clade an ancestor and all its descendants Outgroup a taxon known to have branched off earliest, to show which traits are ancestral Shared derived trait a new feature that appeared in an ancestor and is passed to its descendants OrderBuilding a cladogram from traits
- Choose the taxa and an outgroup.
- Make a table of which taxa have which traits.
- Traits shared by all taxa are ancestral, and give no branching.
- The trait shared by the fewest taxa is placed nearest the tip; the more widely shared, nearer the root.
- Check against DNA data, and choose the tree needing the fewest changes: the most parsimonious.
GapsMolecular data
Traits can be misleading, because analogous features arise by convergence. DNA and protein sequences give many more characters, and the number of differences between two species roughly tracks the time since they diverged, which is the idea of a molecular clock. A phylogenetic tree is a hypothesis, which is revised when new data are found.