Question

1. you are interested in understanding the evolution of fish. use the following information to make a character table and then a cladogram for the types of fish listed.

lampreys have ears with semicircular canals for determining position in the water but are jawless and do not have swim bladders or fins. lobe-finned fishes have fins without spines but do have jaws, semicircular canals, and a swim bladder for maintaining depth in the water. sharks have jaws and semicircular canals but no swim bladder or spiny fins. ray-finned fishes have semicircular canals, spines in their fins, a swim bladder, and jaws. hagfish have none of these characteristics.

1. construct the most parsimonious (simplest) cladogram for the five fish groups using the 4 characteristics from the chart.

Answer:

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<reasoning>

Analyze the text descriptions

We extract the presence (Yes) or absence (No) of each trait for the five fish groups:

• Hagfish: "Hagfish have none of these characteristics."
• Jaws: No, Swim bladder: No, Semicircular canals: No, Spines in fins: No.
• Lampreys: "Lampreys have ears with semicircular canals... but are jawless and do not have swim bladders or fins."
• Jaws: No, Swim bladder: No, Semicircular canals: Yes, Spines in fins: No.
• Sharks: "Sharks have jaws and semicircular canals but no swim bladder or spiny fins."
• Jaws: Yes, Swim bladder: No, Semicircular canals: Yes, Spines in fins: No.
• Lobe-finned fishes: "...have fins without spines but do have jaws, semicircular canals, and a swim bladder..."
• Jaws: Yes, Swim bladder: Yes, Semicircular canals: Yes, Spines in fins: No.
• Ray-finned fishes: "...have semicircular canals, spines in their fins, a swim bladder, and jaws."
• Jaws: Yes, Swim bladder: Yes, Semicircular canals: Yes, Spines in fins: Yes.

Using Biological Classification principles, we can organize these shared derived characters (synapomorphies) to establish evolutionary relationships.

Complete the character table

We fill in the table based on the analyzed traits:

• Hagfish: No, No, No, No
• Sharks: Yes, No, Yes, No
• Lampreys: No, No, Yes, No (already partially filled in the image)
• Lobe-finned fishes: Yes, Yes, Yes, No
• Ray-finned fishes: Yes, Yes, Yes, Yes

Determine the cladogram branching order

We count the number of shared derived characters to find the branching sequence:

• Hagfish: 0 traits (Outgroup)
• Lampreys: 1 trait (Semicircular canals)
• Sharks: 2 traits (Semicircular canals, Jaws)
• Lobe-finned fishes: 3 traits (Semicircular canals, Jaws, Swim bladder)
• Ray-finned fishes: 4 traits (Semicircular canals, Jaws, Swim bladder, Spines in fins)

The evolutionary sequence of branching from earliest to latest is:

1. Hagfish (branches off first, before semicircular canals evolve)
2. Lampreys (branches off after semicircular canals, before jaws evolve)
3. Sharks (branches off after jaws, before swim bladder evolves)
4. Lobe-finned fishes (branches off after swim bladder, before spines in fins evolve)
5. Ray-finned fishes (terminal group with all 4 traits)

Map traits to the cladogram nodes

We place the evolutionary innovations (traits) along the main diagonal stem of the cladogram:

• Semicircular canals: Evolved after Hagfish, before Lampreys.
• Jaws: Evolved after Lampreys, before Sharks.
• Swim bladder: Evolved after Sharks, before Lobe-finned fishes.
• Spines in fins: Evolved after Lobe-finned fishes, leading to Ray-finned fishes.

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<answer>

Question 2: Character Table

Group	Jaws	Swim bladder	Semicircular Canals	Spines in fins
Sharks	Yes	No	Yes	No
Lampreys	No	No	Yes	No
Lobe-finned fishes	Yes	Yes	Yes	No
Ray-finned fishes	Yes	Yes	Yes	Yes

---

Question 3: Cladogram Construction

The most parsimonious cladogram branches in the following order from base to tip, with traits appearing sequentially along the main lineage:

                                                    Ray-finned fishes
                                                   /
                                  Lobe-finned     /
                                     fishes      /
                                       \        /
                              Sharks    \      /  (Spines in fins)
                                \        \    /--*
                       Lampreys  \        \  /
                         \        \        \/  (Swim bladder)
                Hagfish   \        \       /--*
                  \        \        \     /
                   \        \        \   /  (Jaws)
                    \        \        \_/--*
                     \        \       /
                      \        \     /  (Semicircular canals)
                       \        \___/--*
                        \       /
                         \     /
                          \   /
                           \_/
                            |

Order of Branching (Left to Right):

1. Hagfish
2. Lampreys
3. Sharks
4. Lobe-finned fishes
5. Ray-finned fishes

Order of Shared Derived Characters (From oldest/lowest node to newest/highest node):

1. Semicircular canals (arises after Hagfish branches off)
2. Jaws (arises after Lampreys branch off)
3. Swim bladder (arises after Sharks branch off)
4. Spines in fins (arises after Lobe-finned fishes branch off)

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