Question

The phylogenetic tree below shows the evolutionary relationships for several vertebrate groups. Use this diagram to answer the following questions.

1. Which group evolved most recently?
2. Which group has been around the longest?
3. Do the marsupials and fish have a direct common ancestor?

Answer in at least 3 complete sentences.

Phylogenetic Tree

Answer 1

1. The group nearest the end or with the shortest stem of a phylogenetic tree has evolved most recently. In this case it is eutherians.

2. The group with the longest stem has been around the longest: fish

3. A direct common ancestor will share the same immediate line, like marsupials and eutherians. Fish and marsupials do not have a common direct ancestor.

Answer 2

Please see below in bold type.

Step-by-step explanation:

1. You can see on the far left the time scale in million years ago (mya). So the further up the division in the phylogenetic tree, the closer to the present time it branched off. Having said this, the branching that appears further up in the tree is that of Eutherians, so we conclude this is the group that evolved most recently.

2. Acording to this logic, the group that has been around the longest must the one that branched off first (or farther down) from the phylogenetic tree. This is the group of the fish.

3. In every branching of the tree there was a common ancestor to the groups above. Consequently, we can see in the tree that marsupials and fish don't have a direct common ancestor, because Birds and Monotremes branched off first before Marsupials appeared. Marsupials did share a direct common ancestor with Eutherians.