Consider these phylogenetic trees. The first tree is based on physical characteristics. The second tree is based on structure, g
2 answers:
Complete question:
Consider these phylogenetic trees. The first tree is based on physical characteristics. The second tree is based on structure, genetics, and evolutionary history. Which can be concluded from a comparison of the two phylogenetic trees?
- Phylogenetic trees are not subject to change.
- Classification can change with new discoveries and evidence.
- Classification does not change with more evidence.
- Phylogenetic trees are inaccurate.
Answer:
2. Classification can change with new discoveries and evidence.
Explanation:
In phylogenetic trees, two species are more related if they have a recent common ancestor. On the other hand, two species will be less related if their common ancestor is not a recent one and is located far away in the tree.
The phylogenetic tree is composed of,
• Lineages → These are the taxonomic groups of interest placed in the extremes of the lines called branches.
• Nodes → These are the ramification points, which are also known as divergence points. They represent the location of the most recent common ancestor.
• Root → This is the older common ancestor that all lineages share. The first one in the tree.
Two or more lineages are more related to each other if they share a recent common ancestor. This means that they all diverge from the same node.
Two or more lineages are less related to each other if they lack a recent common ancestor. This is, the node from which these lineages diverge is placed far away in the tree.
There are also different phylogenetic relationships between lineages.
• Apomorphies
• Plesiomorphies
• Homoplasy
In the exposed example, we have two trees.
- Tree 1 ⇒ based on physical characteristics
- Tree 2 ⇒ based on structure, genetics, and evolutionary history
Tree 1 reflects that the three species share a common ancestor that is far away in history. From this common ancestor (the blue point in the image), the duck first diverged. Later in evolution, Platypus diverged, and finally, Opossum diverged. The three species are morphologically well-differentiated from each other.
Tree 2 suggests a common ancestor of the three species (the blue point in the image), placed far away in history. From this common ancestor, the duck first diverged. But later in evolution, there was a second branch that diverged, and later originated Platypus and Opossum. According to the information provided by structure, genetics, and evolutionary history, Platypus and Opossum share a most recent common ancestor (the red point in the image).
Both trees provide equally important information. However, tree 2 is more detailed about evolutionary events because it involves many aspects of the animals´ history. Using one of the trees or the other, or both, will depend on the goals of the experiment.
The conclusion we can get from this comparison is that as long as there are discoveries and scientific advances, there will be a constant influx of information useful to recreate or explain evolution. Classification will keep changing with discoveries and evidence.
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