Problem 6 - Biology: Science for Life with Physiology

Question

The DNA sequence for the same gene found in several species of mammals ______ A. is identical among all species; B. is equally different between all pairs of mammal species; \(\mathrm{C}\). is more similar between closely related species than between distantly related species; D. provides evidence for the hypothesis of common descent; E. more than one of the above is correct.

Step-by-Step Solution

Answer

E. More than one of the above is correct (both C and D).

Step 1: Understanding the Question

The question asks about the patterns you might observe in the DNA sequences of the same gene across different mammal species. We're comparing these genes to see what they can tell us about the relationships among species.

Step 2: Analyzing Option A

Option A suggests that the DNA sequence is identical among all specie. This is unlikely because genetic variations do exist across different mammal species.

Step 3: Examining Option B

Option B suggests that the differences in DNA are the same between all pairs of mammal species. This implies a uniform level of difference which is usually not the case due to varying degrees of relatedness.

Step 4: Evaluating Option C

Option C states that DNA is more similar between closely related species than between distantly related species. This aligns with how genetic similarity tends to correlate with evolutionary relationships.

Step 5: Reviewing Option D

Option D indicates that these DNA sequences provide evidence for common descent. This is correct because shared genetic sequences support the concept of a common ancestor for different species.

Step 6: Assessing Option E

Option E suggests that more than one statement is correct. Both Options C and D are supported by evolutionary theory, suggesting common patterns in DNA and evidence for common descent.

Key Concepts

Mammal Species Comparison

When comparing mammal species, scientists often look at the DNA sequences of specific genes to understand how these species are related. By examining the genetic material of different animals, we can determine which species share similar genetics. This helps indicate their evolutionary closeness. Research has shown that closely related species often share more similarities in their DNA than those that are more distantly related.
For example, the DNA of a chimpanzee is more similar to that of a human than to a mouse. This is because humans and chimpanzees share a more recent common ancestor than either does with mice. Such comparisons allow scientists to construct phylogenetic trees, which display the evolutionary connections among various species.

Evolutionary Relationships

Evolutionary relationships refer to how different species are related through common ancestry and evolutionary processes. DNA comparisons reveal that species with more genetic similarities often share recent common ancestors. This relationship forms the basis of evolutionary biology.
By understanding these connections, scientists can chart the evolutionary history of species across millions of years. Key methods include comparing genetic markers, fossil records, and observing physical traits. For instance, evolutionary relationships clarified the connection between whales and hippos, once thought to be distant due to their distinct habitats, but now known to share a closer mammalian lineage.

Genetic Variations

Genetic variations are the differences in DNA sequences between individuals within a species or between different species. These variations arise due to mutations, gene flow, and sexual reproduction. They are crucial for a population's ability to adapt to changing environments.
Variations create diversity within species, leading to differences in physical characteristics, behaviors, and abilities to resist diseases. In mammals, these differences can be small, like fur color changes, or significant, such as differing metabolic processes. Studying genetic variations aids in understanding how species evolve over time and how they might react to environmental pressures.

Common Descent

Common descent is the scientific theory that explains how all living organisms on Earth descended from a common ancestor. This concept is supported by various types of evidence, including genetic information, anatomical similarities, and fossil records. When a gene sequence is shared between different species, it suggests they have inherited it from a shared ancestor.
Furthermore, the greater the degree of similarity in genetic sequences, the more closely related the species are considered to be. This principle underlies the idea that species with a high degree of DNA similarity likely diverged from each other more recently in evolutionary history. Such insights are crucial for mapping the intricate tree of life, revealing how diverse species are interconnected through time.