ASM104 Spring 2019
Name __________________________
Lab 6: Systematics
Part 1. Introduction to a phylogeny
A phylogeny is a diagram that shows the evolutionary relationships of a group of
organisms. A clade is group that contains an ancestor and ALL of its descendants. A
clade is monophyletic, meaning it contains an ancestor and all of its descendants.
Instructions: Examine the phylogeny provided below, and answer the questions that
follow.
1. Do taxa E, F, and G (BY THEMSELVES) form a monophyletic group (clade)?
______________________
2. What about if Ancestors 2 & 3 are included? _________________
3. There are three clades in this phylogeny. Describe ONE by listing the taxa
included in it.
_____________________________________
4. Is Trait 1 homologous or analogous in taxa E, F, and G? ____________________
5. Is Trait 2 homologous or analogous in taxa G and D? ____________________
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Part 2. Creating a phylogeny
Instructions: Using the information on character states given in Table 1, fill in the blanks
on the phylogeny. Be sure to answer the questions that follow.
Table 1: Vertebrate characteristics
Trait
Lobefinned fish
Frog
Turtle
Kangaroo
Mouse
Human
Backbone
Yes
Yes
Yes
Yes
Yes
Yes
Legs
No
Yes
Yes
Yes
Yes
Yes
Outside
mother
Outside
mother
Outside
mother
Inside
mother
Inside mother
Inside
mother
Hair
No
No
No
Yes
Yes
Yes
Presence of
pouch
No
No
No
Yes
No
No
Presence of
tail in adult
Yes
No
Yes
Yes
Yes
No
Place fetus
develops
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1. Are any of the traits unique AND derived for a particular species? If so, which trait and
which species?
2. What is a derived trait shared by kangaroos, mice, and humans only?
3. Is lack of a tail homologous or analogous for the frog and the human?
4. The presence of a backbone is an example of which kind of trait for all the species on the
phylogeny?
Part 3. Determining character states: an introduction to primate systematics
Instructions: Compare the six labeled skulls and fill in the chart by assigning character
states to the characters using 0, 1, or 2. Then, use the information from the completed
chart to answer the following questions.
Score the characters in the following manner:
Post-orbital bar:
0 = absent
1 = present
Post-orbital closure:
0 = absent
1 = present
Tooth comb:
0 = absent
1 = present
Dental formula:
0 = 2.1.3.3. 1 = 2.1.2.3. 2 = other
Position of foramen magnum:
0 = back of skull 1 = bottom of skull
Table 2: characteristics
Skull A
Skull B
Skull C
Skull D
Skull E
Skull F
Post-orbital bar
Post-orbital closure
Tooth comb
Dental formula
Position of foramen
magnum
1. Skulls B, C, D, E, and F are primates. Which character state is a shared derived
feature for all primates (i.e., which character state do all primates share)?
Note: All primates living and extinct have this feature.
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2. Skull B is a strepsirhine primate. Skulls C, D, E, and F are haplorhine primates.
Which two character states differ between haplorhine and strepsirhine primates?
3. Skull C is a platyrrhine primate, and skulls D, E, and F are catarrhine primates.
What character state differs between platyrrhines and catarrhines?
4. Skull F is from a type of catarrhine known as a hominin. What character state is
unique and derived for skull F?
Part 4. Classification
There are two components to systematics: phylogeny reconstruction and classification.
Classification refers to how we organize our information about creatures. It is possible to
organize creatures in many ways- it depends on what information the biologist thinks is
most important to convey. In lecture, you learned about two methods of classification:
cladistics and evolutionary systematics. Answer the following questions that
differentiate between the two methods:
1. What is the primary information conveyed in a cladistic classification?
2. What type of trait is used to generate a cladistic classification?
3. What types of information are conveyed in an evolutionary systematics
classification?
4. What three types of traits are used to generate an evolutionary systematics
classification?
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