Question

name: camilla b
understanding cladograms as models
lab #
cladograms are models of evolutionary history or relationships between organisms that work similar to a family tree. they are constructed based on genetic similarities, physical traits, information gained from the fossil record and biochemical traits (for example a protein found in the blood).
using the cladogram below, answer the questions that follow.
present
time
past

1. what does the arrow in this model represent? ________
2. where in the model will you find the species of finches that are still alive today? circle one. at the top at the bottom
3. which finch is the common ancestor to all others depicted on the tree? ________
4. in the model above put a square box around a finch that is extinct.
5. a more recent common ancestor means that two species are more related than a common ancestor in the past. which birds that are alive in the present day are most related? ________
6. in the model above, circle the finch that would be the common ancestor to finches 7, 8, & 2?

Explanation:

1. The arrow represents the passage of time going from the past to the present.
2. Species alive today are at the top as time progresses upwards in the cladogram.
3. The common - ancestor to all is the finch at the bottom - most point, which is finch 1.
4. Any of the non - topmost finches can be considered extinct as they are from the past. For example, finch 2 or 3 in the middle layers can be boxed as extinct.
5. Birds 5 and 6 are most related as they have the most recent common ancestor among the present - day birds.
6. The common ancestor to finches 7, 8, and 2 is the finch from which their branches diverge, which is the finch labeled 2 in the middle layer.

Answer:

1. Passage of time from past to present
2. At the top
3. Finch 1
4. (Box any non - top finch, e.g., finch 2 or 3)
5. Birds 5 and 6
6. Finch 2 (in the middle layer)