How a snail builds its shell

In the picture

1. 1Mantle edge: the tissue that secretes the shell material
2. 2New thin ring: a flexible organic layer, not yet hardened
3. 3Limestone: a source of calcium carbonate
4. 4Leaf: food that also supplies calcium
5. 5Apex: the hatchling’s first tiny shell, the oldest part of the spiral

Examples

• A garden snail nibbling chalky stone or eggshell to get calcium
• A snail shell with a thin, fragile lip at the edge while the animal is still growing

Quiz: How a snail builds its shell (Age 14)

1. 1

   How does a snail make new shell material?

   • It makes a flexible organic layer that stays soft and never hardens
   • It makes a flexible organic layer first, then hardens it with calcium carbonate
   • It makes hard calcium carbonate first, then adds a flexible layer on top
2. 2

   Because a snail’s shell grows at the rim, where is the oldest part of the shell?

   • Spread evenly over the whole shell
   • At the tip of the spiral
   • At the rim of the opening
3. 3

   Where does a snail get the calcium carbonate that hardens its shell?

   • From water it absorbs through its foot
   • From the food it eats and from limestone
   • From sunlight and rain

The answers, each with its explanation, are in the app. This quiz is free there while the lesson is in the free week.