Problem 4 - Campbell Biology

Question

Application/analysis Bird guides once listed the myrtle warbler and Audubon's warbler as distinct species. Recently, these birds have been classified as eastern and western forms of a single species, the yellow-rumped warbler. Which of the following pieces of evidence, if true, would be cause for this reclassification? (A) The two forms interbreed often in nature, and their offspring survive and reproduce well. (B) The two forms live in similar habitats and have similar food requirements. (C) Different mutations begin to distinguish the gene pools of the separated populations. (D) Gene flow between the two populations is extensive.

Step-by-Step Solution

Answer

Option (A) - The two forms interbreed often in nature, and their offspring survive and reproduce well.

Step 1: Understand the question

The problem is asking for evidence that would support the reclassification of two warbler forms into a single species. Focus on identifying evidence that would suggest these two forms are not distinct species.

Step 1: Analyze Option (A)

Consider if frequent interbreeding and successful reproduction between the two forms support reclassification. If the offspring are viable and fertile, it suggests the two forms are not sufficiently different to be considered separate species.

Step 2: Analyze Option (B)

Evaluate if living in similar habitats and having similar food requirements support reclassification. Similar ecological niches alone do not necessarily indicate that the two forms are a single species.

Step 3: Analyze Option (C)

Consider if different mutations distinguishing the gene pools support reclassification. Diverging gene pools typically suggest the potential for speciation rather than a single species.

Step 4: Analyze Option (D)

Examine if extensive gene flow between the two populations supports reclassification. Extensive gene flow means interbreeding is common, indicating they are more likely the same species.

Step 6: Conclusion

Options (A) and (D) suggest the two forms are the same species because they focus on interbreeding and gene flow. Out of these, (A) specifically highlights successful reproduction, which is a key indicator of a single species according to the biological species concept.

Key Concepts

interbreeding

Interbreeding refers to the mating between individuals from different populations or groups within a species. When two groups can interbreed and produce viable, fertile offspring, it suggests that they share a close genetic relationship. This is key in determining whether two forms should be classified as separate species or not.

When myrtle warblers and Audubon's warblers interbreed often in nature, and their offspring survive and reproduce successfully, this extensive interbreeding indicates that these two forms are not genetically distinct enough to be considered separate species.

Interbreeding provides a genetic exchange between the populations, promoting genetic diversity and indicating that the populations are compatible on a reproductive level. This further blurs the lines between two supposedly separate species.

gene flow

Gene flow is the transfer of genetic variation from one population to another. For gene flow to occur, individuals from different populations must have opportunities to interbreed. When gene flow is extensive between two groups, it facilitates the mixing of genetic materials, leading to a more homogenized gene pool.

In the case of myrtle warblers and Audubon's warblers, extensive gene flow signifies frequent interbreeding and helps maintain genetic similarities across populations, rather than allowing them to diverge into separate species.

Extensive gene flow prevents the accumulation of distinct genetic differences between groups. As a result, it supports the classification of these two groups as a single species, rather than two distinct ones.

biological species concept

The biological species concept defines a species based on the ability of individuals to interbreed and produce viable, fertile offspring. According to this concept, if two populations can interbreed successfully, they should be considered the same species.

Using this concept, the reclassification of the myrtle warbler and Audubon's warbler to a single species, the yellow-rumped warbler, makes sense if interbreeding results in fertile offspring.

The biological species concept emphasizes reproductive isolation. If this isolation is not present, as evidenced by successful interbreeding and extensive gene flow, these factors indicate that the populations are not distinct species. Therefore, (A) and (D) are critical pieces of evidence supporting their reclassification. The combination of viable offspring from interbreeding and significant gene flow aligns with the principles of the biological species concept.