Question

model 1 - phylogenetic trees
millions of years ago
40 35 30 25 20 15 10 5 0
raccoon
red panda
common ancestor of all modern raccoons, pandas, and bears.
giant panda
spectacled bear
sloth bear
sun bear
black bear
polar bear
brown bear

1. refer to model 1.

a. how long ago did the common ancestor of all the organisms on this phylogenetic tree exist?
b. which two lines diverged 30 million years ago?
c. list all modern descendants of the organism that was alive at the point indicated by the asterisk.
phylogenetic trees
1

1. according to model 1, when did the giant panda line diverge from the line that led to modern bears?
2. according to model 1, what animal shares the most recent common ancestor with the brown bear?
3. in a complete sentence, describe what the branch points and lines in a phylogenetic tree represent.
4. which of the two branches from the common ancestor in model 1 has the most living descendants?
5. according to the phylogenetic tree in model 1, the red panda is most closely related to which

Explanation:

Step1: Analyze the start - point of the tree

The common ancestor is at the start of the tree. Looking at the time scale, it is 40 million years ago.

Step2: Locate 30 million years on the time - scale

At 30 million years ago, the lines of Raccoon and the common ancestor of Red Panda, Pandas and Bears diverged.

Step3: Identify descendants from the asterisk point

The modern descendants from the asterisk - marked point are Sloth Bear, Sun Bear, Black Bear, Polar Bear, Brown Bear.

Step4: Find the divergence of Giant Panda from bear line

The Giant Panda line diverged from the line leading to modern bears 20 million years ago.

Step5: Determine the closest relative of Brown Bear

The Polar Bear shares the most recent common ancestor with the Brown Bear.

Step6: Define branch points and lines

Branch points represent common ancestors and lines represent the evolutionary lineages.

Step7: Count living descendants of branches

The branch leading to Raccoon has 1 living descendant, and the other branch has multiple (Red Panda, Giant Panda, Spectacled Bear, Sloth Bear, Sun Bear, Black Bear, Polar Bear, Brown Bear). So the branch leading to Red Panda, Pandas and Bears has the most living descendants.

Answer:

1. a. 40 million years ago

b. Raccoon and the common ancestor of Red Panda, Pandas and Bears
c. Sloth Bear, Sun Bear, Black Bear, Polar Bear, Brown Bear

1. 20 million years ago
2. Polar Bear
3. Branch points represent common ancestors and lines represent evolutionary lineages.
4. The branch leading to Red Panda, Pandas and Bears
5. (No full question for 6, but based on the tree, it is Raccoon)