Question

paleontologist amane tajika and colleagues analyzed the shells of two marine mollusks called nautilids that were harvested from new caledonia. the researchers found that samples from shell sections that formed before hatching, including sample f04, formed in 20 - 22°c water, whereas samples from sections that formed after hatching, including m27, formed in 13 - 15°c water. these findings are consistent with the temperatures fijian nautilids encounter during their corresponding stages of development. because water temperature varies with depth, a biology student hypothesized that the new caledonian nautilids lay their eggs at approximately the same depth as fijian nautilids do. which finding, if true, would most directly weaken the students hypothesis? a fijian nautilids generally live at lower depths than new caledonian nautilids do, though fijian nautilids migrate to the typical depth of new caledonian nautilids to lay their eggs. b once a nautilid hatches, it is a very mobile animal, so the temperature values reported by tajika and colleagues for the adult nautilids are averages over a potentially large range of depths. c the water temperature at a given depth tends to be lower in waters near new caledonia than it is at that depth in waters near fiji. d there are few locations near fiji with water temperatures of 13 - 15°c that are suitable for nautilid eggs.

Explanation:

The student's hypothesis is that New Caledonian nautilids lay their eggs at approximately the same depth as Fijian nautilids do, based on similar temperature - stage relationships. To weaken this, we need to show that the temperature - depth relationship is different between the two locations.

• Option A: If Fijian nautilids migrate to the depth of New Caledonian nautilids to lay eggs, it actually supports the idea that they lay eggs at the same depth.
• Option B: Talks about adult nautilids' temperature averages, which is not relevant to the egg - laying depth (focus is on pre - hatching stage related to egg - laying depth).
• Option C: If the water temperature at a given depth is lower in New Caledonia than in Fiji, then the fact that pre - hatching (related to egg - laying) temperatures are similar (\(20 - 22^{\circ}C\)) would mean that the egg - laying depths are different. For example, if in Fiji \(20 - 22^{\circ}C\) is at depth \(d_1\), in New Caledonia, to get \(20 - 22^{\circ}C\) (since temperature at a given depth is lower in New Caledonia), the depth for egg - laying (where pre - hatching occurs) would be different from Fiji's. This directly attacks the temperature - depth relationship assumption in the hypothesis.
• Option D: Focuses on locations near Fiji suitable for eggs, not on the depth comparison between New Caledonia and Fiji.

Answer:

C. The water temperature at a given depth tends to be lower in waters near New Caledonia than it is at that depth in waters near Fiji.