Question

All of the features below are features that characterize humans, though very few of them are unique to humans. Rather, most of them are present in our species because of our evolutionary history (they were present in an ancestral species at some point in time, and eventually passed on to us). For example, the bilateral symmetry that characterizes the human body plan is a feature that evolved in a primitive animal species that lived hundreds of millions of years ago; hence, it is a feature that is also shared with all but the most primitive animals (SPONGES, JELLYFISH, HYDRA, CORAL). Many other human features are associated with our evolutionary descent from the much more recent last common ancestor of all living mammals.

For each of the following features, indicate the number corresponding to the node at which the feature evolved. While some of these features evolved multiple times in evolutionary history. For purposes of this exercise, we are only interested in cases in which the particular feature was eventually passed on to humans through a pattern of ancestry and descent.  

Note: Some of the descriptions below are preceded with the term "lack of", indicating that humans do not have these features, but that some of our ancestors did. Place such features at the node at which the given character was lost (after having evolved in an earlier ancestor). For example, "lack of tail" should be placed at the node at which the tail (that evolved at some preceding node) was lost.

OPTIONAL extra credit Name: Each correct answer counts as one point. (Up to 15 pts) Use the "Cladogram of chordate animals" Node Feature amniotic sac (amnion) lack of epipubic bones jaws endothermy hair/fur heterodonty terrestrial limbs lungs malleus and incus bones (in middle ear) notochord lactation pectoral & pelvic appendages single bone (dentary) on each side of the mandible (vs. multiple bones) vertebral column vivipary

Answer 1

amnion	8,9,12
lack of epipubic bones	12
jaws	4,10
endothermy	10
hair/fur	9,10
heterodonty	11
terrestrial limbs	8
lungs	5,7
malleus and incus bones	2,10
notochord	1,2
lactation	11,10
pectoral and pelvic appendages	6
single bone on each side of the mandible	10
vertebral column	3,9
vivipary	4,11