Problem 4 - Campbell Biology

Question

The upper forelimbs of humans and bats have fairly similar skeletal structures, whereas the corresponding bones in whales have very different shapes and proportions. However, genetic data suggest that all three kinds of organisms diverged from a common ancestor at about the same time. Which of the following is the most likely explanation for these data? \begin{equation}\begin{array}{l}{\text { (A) Forelimb evolution was adaptive in people and bats, but }} \\ {\text { not in whales. }} \\ {\text { (B) Natural selection in an aquatic environment resulted in }} \\ {\text { significant changes to whale forelimb anatomy. }} \\ {\text { (C) Genes mutate faster in whales than in humans or bats. }} \\ {\text { (D) Whales are not properly classified as mammals. }}\end{array} \end{equation}

Step-by-Step Solution

Answer

Option (B) is the correct answer. Natural selection in an aquatic environment resulted in significant changes to whale forelimb anatomy.

Step 1: Understand the Question

The question asks for the most likely explanation of why the forelimb structures of humans and bats are similar, while those in whales are different, despite all three having a common ancestor.

Step 2: Analyze the Options

Carefully read each option and think about whether it logically contributes to the explanation. Remember, we need to explain why the forelimbs evolved differently in these organisms.

Step 3: Evaluate Option (A)

Option (A) suggests that forelimb evolution was adaptive in humans and bats, but not in whales. This does not provide a thorough explanation for the significant anatomical changes in whale forelimbs.

Step 4: Evaluate Option (B)

Option (B) suggests that natural selection in an aquatic environment resulted in significant changes to whale forelimb anatomy. This aligns with how adaptation to different environments influences evolutionary changes.

Step 5: Evaluate Option (C)

Option (C) suggests genes mutate faster in whales than in humans or bats. There is no evidence to support this claim in the context provided.

Step 6: Evaluate Option (D)

Option (D) suggests whales are not properly classified as mammals, which is incorrect. Whales are indeed mammals, so this option can be dismissed.

Step 7: Choose the Most Likely Explanation

Based on the evaluation, Option (B) is the best answer. It provides a clear and logical reason related to natural selection and adaptation to an aquatic environment.

Key Concepts

adaptive evolution

Adaptive evolution refers to changes in organisms that enhance their survival and reproductive success in a particular environment. Over time, species adapt to their habitats, leading to variations in physical features. For example, the forelimbs of humans, bats, and whales have evolved differently due to the diverse environments they inhabit. This process is driven by the need to efficiently perform functions necessary for survival. In humans, forelimbs are adapted for tasks such as manipulating objects and tool use. Bats have wings, allowing for flight. Whales have evolved forelimbs suitable for swimming. These variations showcase how adaptive evolution customizes anatomical structures for optimal performance in specific habitats.

Understanding these adaptations helps explain why organisms with a common ancestry can exhibit vastly different physical traits.

natural selection

Natural selection is a fundamental mechanism of evolution where individuals with traits better suited to their environment are more likely to survive and reproduce. Over generations, these advantageous traits become more common within a population. In the case of whales, natural selection in an aquatic environment led to significant changes in their forelimb anatomy. Unlike humans and bats, which retained more similar skeletal structures, whales adapted to an underwater lifestyle. Their forelimbs transformed into flippers, enhancing their swimming capabilities. This example underlines how natural selection acts on existing variations within a species, driving evolutionary changes that result in specialized adaptations over time.

Thus, natural selection explains why organisms like whales develop distinct anatomical traits that enable them to thrive in their unique ecological niches.

anatomical changes

Anatomical changes are physical modifications in the structure of organisms that occur over many generations. These changes result from mutations, genetic drifts, and natural selection acting on populations. The forelimbs of humans, bats, and whales have undergone different anatomical changes due to their distinct lifestyles. Humans developed arms and hands for tasks requiring fine motor skills. Bats possess wings for flight, and whales have flippers adapted for swimming. Each anatomical change serves a specific function that enhances the organism's ability to survive in its environment.

Understanding these anatomical changes is crucial for studying evolutionary biology, as it provides insights into how different species evolve in response to diverse selective pressures.

common ancestry

Common ancestry refers to the idea that different species share a common ancestor in the evolutionary tree. Despite the varied adaptations of humans, bats, and whales, genetic data suggests they all diverged from a common ancestor. This ancestor possessed a basic skeletal structure that, over millions of years, diversified into the unique forelimbs seen today. The concept of common ancestry helps explain the similarities in the basic structure of the forelimbs across these species despite their functional differences.

Recognizing common ancestry is fundamental to evolutionary biology, as it highlights the interconnectedness of life and how evolutionary paths can diverge to produce the vast diversity of organisms we see today.