Question

Salt is notoriously dangerous to land snails; however, some populations of aquatic, freshwater snail have brackish (or a mix of salt and fresh water) water adaptations and live in different parts of a river system. A group of scientists monitored salt concentrations in the habitats of two freshwater snail populations located nearby and recorded the salt level as follows (in ppt, parts per thousand):
Population 1 (Day 1): 0.1 ppt (morning), 0.0 ppt (afternoon), 0.1 ppt (evening)
Population 2 (Day 1): 0.3 ppt (morning), 0.5 ppt (afternoon), 0.2 ppt (evening)
In 3-5 sentences, 1) describe in which population you'd expect to see more adaptations for salt water and 2) explain how such adaptations would become more common in this population.

Answer 1

1) Based on the salt concentrations recorded, you would expect to see more adaptations for salt water in Population 2. This is because Population 2 has higher salt concentrations compared to Population 1 throughout the day.
2) Such adaptations would become more common in Population 2 through natural selection. Snails with traits that allow them to tolerate or thrive in higher salt concentrations would have a higher chance of survival and reproduction in Population 2. Over time, these traits would become more prevalent in the population as individuals with these adaptations have a better chance of passing on their genes.