Self-study
One method of dating the emergence of species is to compare the genetic material of related species. ██████████ ████████ ████ ███ ████ ███████████ ███████ ███ ███████ ███ ██ ████ ██████ ███ ████ ████████ ████ ████████ ████ █ ██████ █████████ █████ █████████ ███████ ████████ ████ █████ ███████ ███ ███████ █████████ ███████ ███ ███ █████ ████ ████████ ██████████ █████████ ████ █████ ███ ████████ ████████ ██ ██ ██ ███████ █████ ████ ████ ███████ █████████ ████ ███ ██████ █████████ ████ ███ ████████ ██ █████████ ████████ ███ ██████ █ ███ ███████ █████ ██████ ████ ██ ███████ █████ ██████ █████ ██████ ████████ ████ ███ █████ ██████
Objective: Identify an Inference
The stimulus tells us that scientists can use genetic comparisons to determine when different animal species diverged. These are our facts:
(1) more genetic similarity indicates a more recent divergence;
(2) bears and raccoons diverged 30-50 million years ago;
(3) red pandas diverged from raccoons (and coatis) several million years after raccoons diverged from bears;
(4) giant pandas diverged from bears 10 million years after red pandas diverged from raccoons.
With all these facts, our goal is to find an answer choice that makes a valid inference. It's difficult to spot a single clear inference off the bat, so process of elimination is a good strategy. We can immediately eliminate any answer choice that brings in new information that wasn't discussed in the stimulus. The correct answer will link together existing information in a new way.
21.
Which one of the following ███ ██ ████████ ████████ ████ ███ ████████
a
Giant pandas and ███ ██████ ███ ████ ███████ ███████ ████ ██████████ ██████████ ███████ ████ █████
(A) relies on new information: what scientists "originally thought." This is never discussed in the stimulus, meaning (A) does not identify a valid inference.
b
Scientists now count ███ █████ █████ ██ ███ ██████ ███████ ██ █████
(B) relies on new information: the idea of an eighth bear species. The stimulus talks about seven bear species plus giant pandas; we have no grounds to infer that scientists have now rolled giant pandas into the group of bears.
c
It is possible ██ ██████████ ██████ █ ██████ ██ ████ █ ███ ██████ ███ ██████ ██ ██████████ ██ ███████ ████████
(C) goes too far in representing the stimulus. The closest timing in the stimulus is that red pandas diverged from raccoons a few million years after raccoons diverged from bears. That definitely doesn't let us infer accuracy within "a few years."
d
Scientists have found ████ █████ ██████ ███ ████ ███████ ███████████ ██ █████ ████ ██ █████████
(D) combines facts from the stimulus to make a valid inference. The stimulus says that greater genetic similarity means a more recent divergence. It also says giant pandas diverged from bears relatively recently, definitely more recently than bears diverged from raccoons. That lets us infer that giant pandas must have more genetic similarity to bears than to raccoons.
e
There is substantial █████████ █████ ██████████ ████ █████ ██████ ███ ███ ██████ ███ ███████ ███████ ██ █████████
(E) relies on new information: a "substantial consensus" among scientists. The stimulus just discusses one scientific theory about how to determine when species diverged. That doesn't let us infer anything about the overall beliefs of the scientific community.