Study Guidance: Plant Evolution and Adaptations to Land (Phylogenetics & Traits)

Q1. Name the two pairs of sister taxa that are present in your tree. For each pair, give one trait that they both share.

Background

Topic: Phylogenetics and Shared Derived Traits

This question is testing your understanding of evolutionary relationships (sister taxa) and the concept of shared derived traits (synapomorphies) in a phylogenetic tree.

Key Terms:

• Sister taxa: Two groups that are each other's closest relatives on a phylogenetic tree.

• Shared trait: A characteristic that both members of a sister pair possess, inherited from their most recent common ancestor.

Step-by-Step Guidance

1. Review your phylogenetic tree and identify the two pairs of taxa that are directly connected as sister groups (i.e., they share a most recent common ancestor not shared with any other group).

2. For each pair, look for a trait that is present in both groups but not in the more distant relatives. This trait should have originated in their most recent common ancestor.

3. Write down the names of the two pairs and the shared trait for each.

4. Double-check that the trait you list is not present in more distantly related groups (it should be a derived trait for that pair).

Try solving on your own before revealing the answer!

Q2. Recall from an earlier class that discussed whether or not the group we call "Fish" is monophyletic. What did we conclude? Why?

Background

Topic: Monophyly and Evolutionary Classification

This question is testing your understanding of what it means for a group to be monophyletic (includes all descendants of a common ancestor) and how this applies to the traditional group "fish."

Key Terms:

• Monophyletic group (clade): A group that includes an ancestor and all of its descendants.

• Paraphyletic group: A group that includes an ancestor and some, but not all, of its descendants.

Step-by-Step Guidance

1. Recall the definition of a monophyletic group and compare it to the traditional definition of "fish."

2. Think about whether "fish" includes all descendants of their most recent common ancestor (e.g., do tetrapods descend from fish ancestors?).

3. Consider what was discussed in class about the evolutionary relationships among fish and other vertebrates.

4. Summarize the conclusion and the reasoning behind it (but do not write the final answer yet).

Try solving on your own before revealing the answer!

Q3. Where on the tree would you indicate the evolution of "segmentation"?

Background

Topic: Evolution of Morphological Traits

This question is testing your ability to map the origin of a specific trait (segmentation) onto a phylogenetic tree.

Key Terms:

• Segmentation: The division of an organism's body into repetitive segments, a trait seen in some animal groups.

• Phylogenetic mapping: Placing the origin of a trait on the evolutionary tree at the point where it first evolved.

Step-by-Step Guidance

1. Identify which groups on your tree possess segmentation (e.g., vertebrates).

2. Find the most recent common ancestor of all segmented groups.

3. Mark the branch point (node) where segmentation first appears.

Try solving on your own before revealing the answer!

Q4. Briefly, what is the significance of the evolution of lobed fins?

Background

Topic: Evolutionary Innovations and Adaptations

This question is testing your understanding of how the evolution of lobed fins contributed to vertebrate evolution, especially in the transition to land.

Key Terms:

• Lobed fins: Fleshy, paired fins with a central bony axis, found in some fish (e.g., coelacanths, lungfish).

• Significance: Consider how this trait may have enabled new functions or habitats.

Step-by-Step Guidance

1. Recall which groups first evolved lobed fins and what their structure allowed compared to ray-finned fish.

2. Think about how lobed fins could have facilitated movement in shallow water or on land.

3. Summarize the evolutionary importance of this trait (but do not write the final answer yet).

Try solving on your own before revealing the answer!

Q5. Briefly, what is the significance of the evolution of the amniotic egg?

Background

Topic: Key Adaptations for Life on Land

This question is testing your understanding of how the amniotic egg enabled vertebrates to reproduce away from water and colonize terrestrial environments.

Key Terms:

• Amniotic egg: An egg with specialized membranes (amnion, chorion, allantois) that protect and nourish the embryo, characteristic of amniotes (reptiles, birds, mammals).

• Significance: Consider how this adaptation allowed vertebrates to lay eggs in dry environments.

Step-by-Step Guidance

1. Recall which groups first evolved the amniotic egg and what advantages it provided over earlier reproductive strategies.

2. Think about how the amniotic egg protects the embryo and supports development on land.

3. Summarize the evolutionary significance of this adaptation (but do not write the final answer yet).

Try solving on your own before revealing the answer!