Problem 5 - Campbell Biology

Question

DNA sequences in many human genes are very similar to the sequences of corresponding genes in chimpanzees. The most likely explanation for this result is that \begin{equation}\begin{array}{l}{\text { (A) humans and chimpanzees share a relatively recent com- }} \\ {\text { mon ancestor. }} \\ {\text { (B) humans evolved from chimpanzees. }} \\ {\text { (C) chimpanzees evolved from humans. }} \\ {\text { (D) convergent evolution led to the DNA similarities. }}\end{array}\end{equation}

Step-by-Step Solution

Answer

(A) Humans and chimpanzees share a relatively recent common ancestor.

Step 1: Understand the Question

The question asks for the most likely explanation of why DNA sequences in many human genes are very similar to those in chimpanzees.

Step 2: Review the Options

Consider each option: (A) Humans and chimpanzees share a common ancestor. (B) Humans evolved from chimpanzees. (C) Chimpanzees evolved from humans. (D) Convergent evolution led to the DNA similarities.

Step 3: Apply Biological Knowledge

Use knowledge of evolution to evaluate the options: - Both (B) and (C) are incorrect because humans did not evolve directly from chimpanzees nor vice versa. - Convergent evolution (option D) refers to different species evolving similar traits independently, which is not the case here as it's about genetic sequences.

Step 4: Identify the Correct Answer

The most scientifically supported explanation is (A), which states that humans and chimpanzees share a relatively recent common ancestor. This explains the DNA similarities due to inheritance from this ancestor.

Key Concepts

Common Ancestor

Humans and chimpanzees have DNA similarities because they share a common ancestor. A common ancestor is an ancient species from which two different species have evolved. In this case, humans and chimpanzees inherited similar DNA from this shared ancestor.

The concept of a common ancestor helps explain why there are genetic similarities among different species. It indicates a point in the evolutionary tree where the paths of the species diverged.

Evolution

Evolution is the process through which species change over time. It's driven by natural selection, where traits that are advantageous for survival become more common in a population.

This process explains how humans and chimpanzees have evolved and adapted to their environments in different ways, despite sharing a common ancestor. Over millions of years, both species developed unique traits, but the genetic similarities remain due to their shared origin.

DNA Similarity

DNA similarity refers to the extent to which the genetic codes of different organisms are alike. For humans and chimpanzees, this similarity is quite high, with around 98-99% of their DNA being identical.

This high degree of similarity is a result of the two species having inherited much of their genetic material from a common ancestor. Scientists can use these genetic sequences to track evolutionary changes and understand the relationships between different species.

Convergent Evolution

Convergent evolution occurs when unrelated species develop similar traits independently, often due to similar environmental pressures. For example, birds and bats both have wings, but they evolved these traits separately.

Unlike the DNA similarity between humans and chimpanzees, which is due to a common ancestor, convergent evolution involves analogous traits rather than shared genetic heritage. Thus, convergent evolution is not the reason for the genetic matches seen in human and chimpanzee DNA sequences.