Question

.The species of hermit crab used in the experiment and a second species of hermit crab are monophyletic. This second species is colorblind. Which of the following scenarios is most likely? A. These two species of hermit crabs do not share a common ancestor. B. Color-blindness is an analogous trait between the two species. C. This second species of hermit crab was influenced by evolutionary pressures of the founder effect. D. Color-blindness is a homologous trait between these two species.

Short answer

D. Color-blindness is a homologous trait between these two species.

Step-by-step solution

- Understand Key Terms

Monophyletic means that the two species share a common ancestor. Analogous traits develop independently in different species due to similar environmental pressures, while homologous traits are inherited from a common ancestor. The founder effect occurs when a new population is established by a small number of individuals.

- Analyze the Information

Since both species are monophyletic, we know they share a common ancestor. This helps us rule out answer A.

- Examine Evolutionary Traits

For color-blindness to be an analogous trait, it should develop independently in both species, but because they share a common ancestor, this is unlikely. So, option B is ruled out.

- Evaluate Evolutionary Pressures

The founder effect could influence traits in a new population, but it's not related to the hereditary nature of color-blindness from a common ancestor. So, option C is ruled out.

- Verify the Correct Scenario

Since both species share a common ancestor, color-blindness is likely a homologous trait inherited from this ancestor. Thus, option D is most likely correct.

Key concepts

Common Ancestor

In evolutionary biology, a common ancestor refers to an ancient species from which two or more species have evolved. Because the two species of hermit crabs mentioned are monophyletic, they share a common ancestor. This shared origin implies that both species descended from a single lineage.
Monophyly is an important concept as it helps scientists understand evolutionary relationships and how traits are passed down. It also tells us that any shared traits between the two hermit crab species, like color-blindness, are likely inherited rather than independently developed.

Analogous Traits

Analogous traits are characteristics that appear similar but have evolved independently in different species due to similar environmental pressures rather than from a common ancestor. This concept is essential to distinguish from homologous traits for correct interpretation of evolutionary history.
For example, the wings of birds and bats are analogous traits. They serve similar functions and appear similar due to convergent evolution, but birds and bats did not inherit wings from a common ancestor. Applying this to the hermit crabs, color-blindness being analogous is unlikely since the species are monophyletic and share a common ancestor.

Homologous Traits

Homologous traits are features that are inherited from a common ancestor. These traits may not always serve the same function in the descendant species but have a similar underlying structure due to shared ancestry.
The presence of color-blindness in both species of hermit crabs is likely a homologous trait. This means that the trait was passed down from the common ancestor of both species, making it an inherited characteristic rather than independently developed. This helps in understanding why certain traits remain consistent across related species.

Founder Effect

The founder effect is an evolutionary phenomenon where a new population is established by a very small number of individuals from a larger population. This small group may carry only a tiny portion of the genetic diversity of the original population, leading to reduced genetic variability.
This concept is not directly related to the trait of color-blindness in the hermit crabs. Founder effect tends to influence population genetics more broadly, affecting traits randomly due to the limited genetic pool. Thus, for the hermit crabs, color-blindness is a hereditary trait that does not result from the founder effect.

Monophyletic

A monophyletic group consists of an ancestor and all its descendants, which is essential in understanding evolutionary relationships. Because the two species of hermit crabs are monophyletic, they both originate from a single common ancestor.
This helps in determining the likelihood of traits being inherited versus developed independently. In the case of these hermit crabs, their monophyletic status suggests that shared traits like color-blindness are homologous, having been passed down from their shared ancestor rather than arising separately through convergent evolution.