Question 1·Easy·Inferences
In 1995, gray wolves were reintroduced to Yellowstone National Park after having been absent for nearly seventy years. Over the next fifteen years, ecologists observed a noticeable decline in the park’s elk population, followed by a marked increase in young willow and aspen trees growing along riverbanks. The researchers concluded that the wolves’ presence changed elk behavior and numbers, which in turn allowed more tree saplings to survive.
Which of the following inferences is most strongly supported by this information?
For inference questions, first underline or note the key facts and any stated cause-and-effect relationships in the passage. Then, test each answer choice by asking, "Can I clearly back this up with what is actually written?" Eliminate choices that (1) add new information not mentioned, (2) exaggerate with absolute words like "all" or "never," or (3) contradict the passage. The correct choice will restate or slightly extend the passage’s ideas without going beyond the evidence.
Hints
Locate the cause-and-effect relationship
Reread the sentences that describe what changed after the wolves were reintroduced. What happened to the elk, and what happened to the trees?
Focus on what the researchers concluded
Pay special attention to the last sentence about what the researchers concluded from their observations. What did they say the wolves' presence led to?
Watch for extreme or new information in the answer choices
Look for choices that use absolute language like "all" or that introduce ideas (like other animals or flooding) that are not mentioned in the passage.
Think about direct vs. indirect effects
Did the wolves directly act on the trees, or did they change something else that then affected the trees? Keep that in mind as you compare the choices.
Step-by-step Explanation
Restate the key facts from the passage
First, list the important information:
- Gray wolves were reintroduced in 1995.
- Over fifteen years, ecologists saw a decline in the elk population.
- After that, they observed more young willow and aspen trees along riverbanks.
- Researchers concluded that the wolves changed elk behavior and numbers, and this change allowed more tree saplings to survive.
Understand what the question is asking
The question asks for an inference that is most strongly supported by the information.
This means:
- The correct answer must be something you can logically conclude from the passage.
- It should be directly connected to the facts given.
- It cannot introduce new, unsupported ideas or exaggerations.
Identify the cause-and-effect chain
Look at how the passage connects the ideas:
- Wolves arrive → elk behavior and numbers change (elk population declines).
- Elk change → more tree saplings survive (more young willow and aspen trees grow).
So, there is an indirect chain:
- Wolves affect elk → elk affect trees.
Any good answer will reflect this indirect effect of wolves on the trees.
Check each answer against the passage and choose the supported inference
Now compare each option to the passage:
- A) Says all elk were eliminated. The passage only says there was a decline, not that elk disappeared.
- B) Says wolves caused flooding by digging dens. The passage never mentions flooding or dens.
- C) Claims wolves preferred hunting beavers. Beavers are never mentioned.
- D) Says the wolves indirectly promoted the growth of certain trees. This matches the described chain: wolves → fewer/different elk behavior → more tree saplings surviving.
Therefore, the best supported inference is D) The wolves indirectly promoted the growth of certain trees in the park.