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.