Cladograms and Phylogenic Trees: Using Evidence to Determine Evolutionary Relationships
DO NOT WRITE ON THIS FORM: WRITE ALL ANSWERS & DRAW ALL DIAGRAMS ON SEPARATE PAPER
INTRO:
Cladistics is the study of evolutionary classification. Cladograms show evolutionary relationships among organisms.
Comparative morphology investigates characteristics for homology and analogy to determine which organisms share a
recent common ancestor. A cladogram will begin by grouping organisms based on characteristics displayed by ALL the
members of the group. Subsequently, the larger group will contain increasingly smaller groups that share the traits of
the groups before them. However, they also exhibit distinct changes as the new species evolve. Further, molecular
evidence from genes, which rarely mutate can provide molecular clocks that tell us how long ago organism diverged,
unlocking the secrets of organisms that may have similar convergent morphology but do not share a recent common
ancestor.
Fig 1
1.
Which organisms in the cladogram in Figure 1 have fur and mammary glands?
2. Which organisms in the cladogram in Figure 1 have jaws?
3. Based on the cladogram in Figure 1, which shared a common ancestor most recently—a mouse and a lizard or a
mouse and a perch?
4. Which two organisms would you expect to have a closer matching DNA sequence for a gene that is NOT under
selective pressure in nature—a hagfish and a pigeon or a hagfish and a salamander?
Part I:
Morphological Evidence: Using your text and prior knowledge (what you already know), determine the
morphological characteristics of the organisms in the following table. For every characteristic the organism
possesses, put a checkmark in that box.
Organism
Eukaryote Multicellular Segmented Jaws
Body
Limbs
Hair
Placenta
Common
Ancestor
Amoeba
Kangaroo
Earthworm
Cat
Shark
Dolphin
Lizard
Sponge
Has
Bone
# of
differences
from
Ancestor
N/A
Given the data you have compared, draw a cladogram based on these morphological
characterisitics.
Part II:
Molecular Evidence: Cytochrome c is a protein located in the mitochondria of cells involved with cellular
respiration. Compare each organism’s cytochrome c DNA sequences with the ancestor cell and each other. Circle or
highlight the differences (mutations) present in the cytochrome c DNA sequences from the Ancestor cell.
Cytochrome c DNA Sequence Data:
Organism
DNA Sequence
Ancestor
Earthworm
ATTAGCGACCAGTATATCCTACAATCCGTCTACTTCATT
ATTAGCGACCAGTTTATCCTACAATCCCGTCTACTTCAT
CTAATCCCCCCGTTTATCCTACTTTCCCATCTACTAAGT
CTTATCGACCCGTTTATCCTACATTCCCGTCTACTTCGT
Cat
TTAATCCCCCCGTTTATCCTACTTTCCCATCTACTAAGT
Shark
CTTATCCCCCCGTTTATCCTACTTTCCCGTCTACTTCGT
Dolphin
CTAATCCCCCCGTTTATCCTACTTTCCCATGTAGTAAGT
Lizard
CTAATCCCCCCGTTTATCCTACTTTCCCGTCTACTTCGT
Sponge
ATTATCGACCAGTTTATCCTACATTCCCGTCTACTTCGT
Amoeba
Kangaroo
Using the above data: create a cladogram based on molecular evidence.
Comparing Part I and Part II:
1.
How did your morphological cladogram compare with your cladogram based on the cytochrome c DNA
evidence?
2. Compare and contrast convergent evolution with divergent evolution.
Which two organisms show convergent evolution in the cladogram from part II?
Why might these two organisms have similar morphology despite not sharing a recent ancestor?
3. Which type of evidence is most accurate in determining evolutionary relationships? Morphology or molecular?
Why?
Part III:
A phylogenetic tree is a tree showing the evolutionary interrelationships among various species that are
believed to have a common ancestor. A phylogenetic tree is a form of a cladogram. In a phylogenetic tree, each node
with decendants represents the most recent common ancestor of the descendents, and edge lengths correspond to
time estimates. An
example of a
phylogenetic tree is
below.
Phylogenetic trees requires each species to be compared to each other as in the following chart.
Organism
Horse
Donkey
Whale
Chicken
Penguin
Snake
Moth
Yeast
Wheat
Horse
0
Donkey
1
0
Whale
5
4
0
Chicken
11
10
9
0
Penguin
13
2
10
3
0
Snake
21
20
18
18
17
0
Moth
29
28
27
29
27
29
0
Yeast
45
46
45
46
45
46
48
0
Wheat
46
45
44
46
46
46
45
47
0
As a class lets demonstrate this process. Use the data from the chart above to complete the cladogram outline below:
Now you will make a phylogenetic tree for the different species you’ve studied in reference to the differences in their
Cytochrome c proteins (Part II DNA comparison). In order to do this you will not only have to compare the DNA
sequences to the ancestor DNA but to each other’s DNA. Use a chart like below to record the number of differences
between each pair compared. Use the data you collect to create a phylogenetic tree (cladogram)
Organism
Common
Ancestor
Amoeba
Kangaroo
Earthworm
Cat
Shark
Dolphin
Lizard
Sponge
Common
Ancestor
0
Amoeba
Kangaroo
Earthworm Cat
Shark
Dolphin
Lizard
Draw out your phylogenetic tree.
1.
How does it compare to the first two cladograms you created?
a. How is it similar?
b. How is it different?
c. Which provides more information/detail?
d. How accurate do you believe this process to be? Where might the inaccuracies occur?
Sponge
0