Snails’ ancestors are one of the earliest known types of animals in the world. All land snails are gastropod mollusks, meaning that they belong to the same group of octopuses, which are part of the phylum Mollusca. The life expectancy of snails in the wild is about 3 to 7 years, but in captivity, they can live up to 10-15 years or even more.Snail shell is made of calcium carbonate and keeps growing as long as the snail grows. They keep adding more calcium carbonate to the edge until the snail reaches adult size. When snails multiply and damage crops or in some way affect the species of a region or the human being, they are considered pests.