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):

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 data provided, it can be inferred that Population 2 is more likely to have adaptations for salt water. This is because the recorded salt concentrations in Population 2 are consistently higher than those in Population 1 throughout the day.

2) In Population 2, snails with adaptations for salt water would have a higher chance of survival and reproductive success compared to those without such adaptations. This is because the higher salt concentrations in the habitat would pose a greater selection pressure on the snails, favoring individuals with traits that allow them to tolerate or even benefit from brackish water conditions. Over time, through natural selection, these adaptations would become more common in the population as they provide a survival advantage in the given environment.