Question

One method of dating the emergence of species is to compare the genetic material of related species. Scientists theorize that the more genetically similar two species are to each other, the more recently they diverged from a common ancestor. After comparing genetic material from giant pandas, red pandas, raccoons, coatis, and all seven bear species, scientists concluded that bears and raccoons diverged 30 to 50 million years ago. They further concluded that red pandas separated from the ancestor of today's raccoons and coatis a few million years later, some 10 million years before giant pandas diverged from the other bears. Which one of the following can be properly inferred from the passage? (A) Giant pandas and red pandas are more closely related than scientists originally thought they were. (B) Scientists now count the giant panda as the eighth species of bear. (C) It is possible to determine, within a margin of just a few years, the timing of divergence of various species. (D) Scientists have found that giant pandas are more similar genetically to bears than to raccoons. (E) There is substantial consensus among scientists that giant pandas and red pandas are equally related to raccoons.

Short answer

D: Scientists have found that giant pandas are more similar genetically to bears than to raccoons.

Step-by-step solution

Understanding the Passage

The passage provides information about the genetic similarities between different species: giant pandas, red pandas, raccoons, coatis, and bears. It explains that the time of divergence from a common ancestor was calculated based on genetic similarities.

Identifying Key Details

Key details include: bears and raccoons diverged 30-50 million years ago; red pandas separated from the raccoons and coatis a few million years later; and the giant pandas diverged from the bears 10 million years after the red pandas diverged.

Analyzing Option A

Option A suggests a closer relation between giant and red pandas than originally thought, but the passage does not compare the two pandas directly, so this option cannot be inferred from the passage.

Analyzing Option B

Option B claims scientists now consider giant pandas as the eighth species of bear. The passage does not mention this classification, so this cannot be inferred.

Analyzing Option C

Option C states the possibility to determine species divergence within a few years margin, but the passage only mentions divergence in tens of millions of years, implying a larger margin, so this cannot be inferred.

Analyzing Option D

Option D states that scientists have found that giant pandas are more similar genetically to bears than raccoons. Since the passage discusses divergence timing and includes giant pandas within the group of bears, this can reasonably be inferred.

Analyzing Option E

Option E claims a consensus on the relation of pandas to raccoons, but the passage does not discuss any consensus nor compare giant and red pandas equally to raccoons, so this cannot be inferred.

Selecting the Correct Inference

After analyzing each option, Option D is the only one that can be reasonably inferred based on the passage's discussion of divergence timing and implied genetic similarity.

Key concepts

species divergence

Species divergence refers to the splitting of a common ancestral species into two or more distinct species over time. This process is a key mechanism in evolution. When species diverge, they accumulate different genetic changes that lead to unique characteristics.
Understanding when species diverged can provide insights into their evolutionary history. Scientists often date the divergence by comparing genetic similarities between species. Here’s how it typically works:

• Scientists compare DNA sequences of different species to identify genetic markers.
• Over time, these markers accumulate mutations at a predictable rate.
• By assessing the number of differences, scientists estimate how long ago the species shared a common ancestor.

In our example, the genetic material comparison between giant pandas, red pandas, and bears helps scientists determine their points of divergence. In essence, species divergence allows scientists to trace back the evolutionary paths of various living organisms.

genetic similarity

The concept of genetic similarity plays a crucial role in understanding the evolutionary relationships between species. When scientists talk about genetic similarity, they're referring to the degree to which the DNA sequences of two species are alike. The more similar these sequences, the more recently the species are thought to have diverged from a common ancestor.
Genetic similarity can be quickly checked through various methods:

• DNA sequencing to determine base pair order in each species.
• Comparative mapping of genes to find commonalities.
• Using molecular clocks to estimate the time of divergence.

In the passage, the scientists conclude genetic similarities indicate a timeline. For instance, bears and raccoons shared a common ancestor 30-50 million years ago. Such findings help clarify complex relationships within the animal kingdom and enhance our understanding of life’s history on Earth.

inferential reasoning

Inferential reasoning is a critical thinking process used to draw conclusions based on evidence and reasoning rather than explicit statements. It involves identifying premises within a context and deducing logical outcomes. For the LSAT and similar tests, practicing this kind of reasoning helps interpret passage information correctly.
When answering the exercise, inferential reasoning was key:

• The passage introduces genetic analysis as the foundation for divergence conclusions.
• Through logical deduction, one infers that genetic similarity correlates with evolutionary timelines.
• Reading between the lines helps deduce that giant pandas are genetically closer to other bears than to raccoons.

In essence, inferential reasoning in logical puzzles requires understanding implied meanings. Looking beyond the explicit reveals connections that prompt accurate inferences and solutions.

comparison of species

The comparison of species is an essential element in biological studies and ecological research. Scientists capitalized on this technique to address evolutionary questions like those illustrated in the exercise. The focus is usually on comparing genetic material to assess differences and commonalities, which, in turn, sheds light on their lineage.

• Genetic sequences are compared to identify shared ancestry.
• This approach highlights significant evolutionary paths and events.
• The outcome is a phylogenetic tree, mapping related species on a branching diagram.

Such comparative analyses answer questions like how closely related two species are or the approximate time they parted from mutual ancestry. In the passage, species comparison between giant pandas, red pandas, and bears reveals their evolutionary histories. Scientists deduced divergence timings by thoroughly analyzing the genetic links, thus crafting a clearer picture of these creatures' past connections.