Question

Salt is dangerous to land snails. It will rapidly kill them. However, some populations of aquatic, freshwater snail have adapatations that allow them to live in a mix of salt and fresh water. This allows them to live in different parts of a river system. A group of scientists monitored salt concentrations in the habitats of two freshwater snail populations. They recorded the salt level as follows (in ppt, parts per thousand):

Location 1 (Day 1): 0.1 ppt (morning), 0.0 ppt (afternoon), 0.1 ppt (evening)

Location 2 (Day 1): 0.3 ppt (morning), 0.5 ppt (afternoon), 0.2 ppt (evening)

In 3–5 sentences, describe in which population you'd expect to see more adaptations for salt water. Make sure to also explain how such adaptations would become more common in this population.

(4 points)

Answer 1

I would expect to see more adaptations for salt tolerance in the freshwater snail population at Location 2, which experienced higher salt concentrations, ranging from 0.2 to 0.5 ppt throughout the day. Over time, individuals with genetic traits that allow them to survive and thrive in saltier environments would have a selective advantage, leading to increased reproductive success. As a result, these advantageous traits would become more common in subsequent generations through the process of natural selection, allowing the population to better adapt to fluctuating salinity levels in their habitat.