Question

Many species in mountain ranges are shifting their ranges to higher, cooler elevations in response to warming temperatures because of climate change.

The graph above shows how the midpoint of elevational range in the year 2025 is related to the midpoint of the elevational range in the year 2000 for species in temperate (open circle) and tropical (solid circle) mountain ranges. Each point represents a species, and the dashed line is the 1:1 or the identity line (with intercept = 0 and slope = 1). Which one of the following statements is consistent with the above graph?

• A. Tropical species are more sensitive than temperate species to temperature change
• B. Temperate species are more sensitive than tropical species to temperature change
• C. Both tropical and temperate species are equally sensitive to temperature change
• D. No conclusion can be reached about the relative sensitivities of tropical and temperate species to temperature change

Hint:

Distance above the 1:1 identity line shows how much a species range has shifted upward; compare that distance for solid (tropical) versus open (temperate) points.

Answer 1

The Correct Option is A

Step 1: Understand what the identity line means.
The dashed 1:1 line marks every point where the 2025 elevation midpoint equals the 2000 elevation midpoint, in other words, no change at all. A species point that sits above this line has moved to a higher elevation by 2025, and the farther above the line it sits, the bigger the upward shift.

Step 2: Look at the tropical species (solid circles).
The solid circles sit well above the dashed line across the whole range of the plot, and many of them sit far from the line, showing large upward shifts in elevation between 2000 and 2025.

Step 3: Look at the temperate species (open circles).
The open circles cluster much closer to the dashed line, with only a small, fairly consistent upward shift. Several open circles sit almost right on the identity line, meaning barely any change in elevation at all.

Step 4: Compare the two groups.
Since the vertical distance above the identity line represents how much a species has shifted upslope, and tropical species are consistently farther above the line than temperate species, tropical species are moving upslope more than temperate species in response to the same warming trend.

Step 5: Rule out the other options.
Option (B) claims the opposite pattern, which the graph does not show. Option (C) would require both groups to show the same distance from the identity line, but they clearly do not. Option (D) is wrong because the graph gives a clear, readable pattern, so a conclusion can be drawn.

Step 6: Final Answer.
\[ \boxed{\text{Tropical species are more sensitive than temperate species to temperature change}} \]