Structure and Function is my answer
They may have ran out of oxygen, or they may not have been water dwelling snails, as not all are, lack of food, no flow of water into and out of the tank would cause them to run out of oxygen.
Answer:
Stabilizing selection
Explanation:
Stabilizing selection may be defined as the type of a natural selection where the genetic diversity decreases and the population mean stabilizes on the particular value. It occurs to the individual trait when an extreme of the trait are selected against.
In birds, the bright color males attract more mates for survival but they also attract more predators. Over generation, the highest frequency color is for the intermediate coloring males.
