Question

The fact that DNA sequences are more similar in more closely related organisms is evidence of what? a. optimal design in organisms b. adaptation c. mutation d. descent with modification

Short answer

The correct answer is (d) descent with modification, as it best explains why DNA sequences are more similar in more closely related organisms.

Step-by-step solution

Identify the question asked

The question asks about the reason why DNA sequences are more similar in more closely related organisms.

Analyze the choices

a. Optimal design in organisms: This choice implies that the similarity in DNA sequences is due to organisms having an ideal design. However, the word "optimal" doesn't explain the relationship between the organisms. b. Adaptation: Adaptation refers to the process by which organisms change over time in response to their environment. While it plays a role in the evolution of species, it does not specifically explain why more closely related organisms have more similar DNA sequences. c. Mutation: Mutation is a change in the genetic material of an organism. While mutations are essential for the process of evolution, it does not adequately explain why more closely related organisms have more similar DNA sequences. d. Descent with modification: This choice implies that organisms inherit their traits from their ancestors but with some changes (modifications) due to various evolutionary factors like mutations, adaptations, and natural selection. This explanation directly refers to the relationship between organisms and their DNA sequences' similarity.

Choose the correct answer

Based on the analysis of the given choices, the correct answer is (d) descent with modification, as it best explains why DNA sequences are more similar in more closely related organisms.

Key concepts

Evolutionary Biology

Evolutionary biology is a fascinating field that studies the processes that drive the diversity of life on Earth. It focuses on understanding how different species have evolved over time
and how they are related to one another through common ancestors. The core concept in evolutionary biology is the theory of evolution, as proposed by Charles Darwin.
Evolution involves gradual changes in the genetic makeup of populations, leading to the formation of new species. To fully understand this field, it is important to grasp the mechanisms by which evolution occurs. These mechanisms include:

• Natural selection, where traits that offer a survival or reproductive advantage become more common.
• Mutation, random changes in DNA that may result in new traits.
• Gene flow, the transfer of genetic information between populations.
• Genetic drift, changes in allele frequencies due to random chance.

Together, these mechanisms drive the principle of "descent with modification," meaning that all organisms are related through descent from a common ancestor, with modifications accumulating over time.

DNA Sequence Similarity

DNA sequence similarity is a powerful tool used to understand the evolutionary relationships between organisms. It refers to the degree to which the DNA sequences in the genomes of different organisms are similar to one another.
This similarity can provide evidence for common ancestry and evolutionary connections. When we compare DNA sequences from different species, closely related organisms tend to have a higher degree of similarity in their DNA. This is because DNA sequences change gradually over time
due to mutations and other evolutionary processes, leading to differences in the genetic code. Scientists can use sequence similarity to construct phylogenetic trees, which are diagrams that show the inferred evolutionary relationships between different species.

• Closer branches indicate a more recent common ancestor.
• More dissimilar branches suggest a more distant relationship.

Comparing DNA sequences across species helps us understand how life has evolved and how different species are related through their genetic history.

Closely Related Organisms

Closely related organisms are species that share a relatively recent common ancestor, and therefore have a high degree of similarity in their genetic makeup. When biologists refer to organisms as "closely related," they are often discussing their evolutionary connections. The level of genetic similarity between two species can help determine how closely related they are. This concept is central to constructing evolutionary family trees and understanding biodiversity. A good example of closely related organisms can be seen in the great apes, including humans, chimpanzees, gorillas, and orangutans.

• Humans and chimpanzees share a large percentage of their DNA, indicating they are closely related.
• The closer two species are on the evolutionary tree, the more genetic material they share.

Studying closely related organisms enables scientists to trace back the lineage of species and predict how new species might evolve in the future, all under the overarching principle of descent with modification.