Which environmental factor besides predators might explain differences in pelvic spine development between Bear Paw Lake and Frog Lake, and how would you test it?

Which environmental factor besides predators might explain differences in pelvic spine development between Bear Paw Lake and Frog Lake, and how would you test it?

• A. The freshwater in Frog Lake is lower in calcium and minerals needed to form pelvic spines; test by measuring mineral content of water from both lakes.
• B. Higher water temperature in Frog Lake causes longer spines; test by heating water.
• C. Different fish species in Frog Lake cause spines to grow; test by counting fish species.
• D. Varying pH levels alone determine spine frequency; test by adjusting pH.

Answer: (A)

The main idea here is that the minerals available in the fish’s environment can directly influence how bones form. Pelvic spines are made from calcium-rich material, so if Frog Lake water has lower calcium and other minerals needed for bone growth, developing spines could be smaller or less developed compared with fish from Bear Paw Lake. To test this, measure the mineral content of water from both lakes, focusing on calcium and other key minerals involved in calcification. If Frog Lake water is indeed lower in these minerals, that would provide a plausible environmental explanation for the difference in spine development. For stronger evidence, you could raise fry from both populations in a controlled setup with water that mimics each lake’s mineral profile; if spine differences persist under identical genetics but different water chemistries, minerals are the likely driver. If the differences disappear in the common environment, genetics or other factors may be at play. Other ideas like temperature or pH alone are less direct: temperature can affect growth rates but doesn’t specifically control spine formation, and changing water temperature in a simple test wouldn’t isolate mineral availability. Counting fish species doesn’t directly link to the mineral needed for bone development.

The main idea here is that the minerals available in the fish’s environment can directly influence how bones form. Pelvic spines are made from calcium-rich material, so if Frog Lake water has lower calcium and other minerals needed for bone growth, developing spines could be smaller or less developed compared with fish from Bear Paw Lake.

To test this, measure the mineral content of water from both lakes, focusing on calcium and other key minerals involved in calcification. If Frog Lake water is indeed lower in these minerals, that would provide a plausible environmental explanation for the difference in spine development. For stronger evidence, you could raise fry from both populations in a controlled setup with water that mimics each lake’s mineral profile; if spine differences persist under identical genetics but different water chemistries, minerals are the likely driver. If the differences disappear in the common environment, genetics or other factors may be at play.

Other ideas like temperature or pH alone are less direct: temperature can affect growth rates but doesn’t specifically control spine formation, and changing water temperature in a simple test wouldn’t isolate mineral availability. Counting fish species doesn’t directly link to the mineral needed for bone development.