Exercise 1: Constructing a Cladogram
Use the data below to order organisms and shared apomorphies in the following table into their correct position on the cladogram. Remember, the outgroup is not usually specifically shown in the cladogram.
Create a cladogram for the following species:
|
Trait
|
Outgroup
|
Arachnida
|
Merostomata
|
Pycnogonida
|
|
Number of pairs of legs
|
4
|
4
|
4
|
4
|
|
Cephalothorax
a carapace-like shield |
No
|
Yes
|
Yes
|
Yes
|
|
Telson
|
No
|
No
|
Yes
|
No
|
|
Abdominal appendages
|
Present
|
Reduced or modified
|
Present
|
Present
|
|
Tracheae
|
Absent
|
Present
|
Absent
|
Absent
|