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Table of Contents
A shell is a hard, protective outer covering that has evolved in various marine animals, including mollusks and sea urchins. Crustaceans, turtles, tortoises, and armadillos also have shells. Shells can also be found in food, like eggs, nuts, and fruits. Common types of shells include seashells, snail shells, turtle shells, eggshells, and nutshells.
See the fact file below for more information on Baldur, or you can download our 23-page Baldur worksheet pack to utilize within the classroom or home environment.
Key Facts & Information
TERMINOLOGY
- The shells of marine mollusks such as snails, clams, and oysters are called seashells.
- Seashells are primarily made of calcium.
- Mollusks, or molluscs, are soft-bodied invertebrates belonging to the phylum Mollusca, the second-largest phylum of invertebrate animals.
- Conchology is the study and collection of mollusk shells found in marine, freshwater, and territorial ecosystems.
- People who study conchology are called conchologists.
- Shell collecting is a popular hobby that involves finding, identifying, and collecting shells of mollusks.
- Turtle shells, or tortoiseshells, serve as a shield that protects and encloses a turtle’s vital organs.
- Eggshells are the hard outer layer of an egg which consists mostly of calcium carbonate.
TYPES OF SEASHELLS
- Most seashells found on the seashore are mollusk shells.
- Seashells found on the beach are empty because the animal has already died, and its soft body parts and organs have either decomposed or been eaten by another animal.
- Other seashells are those of brachiopods, crustaceans, barnacles, and horseshoe crabs.
MOLLUSK SHELLS
- While humans have their skeletons inside their bodies, mollusks have their skeletons on the outside.
- There are over 50,000 varieties of mollusk shells, which are found mainly in marine biomes.
- These are also found in freshwater and terrestrial regions.
- Clamshells, snail shells, chiton shells, and tusk shells are types of mollusk shells.
- Clamshells open in a symmetrical manner, with two mirror-image sides or valves connected by a hinge that allows the clam to open.
- On the other hand, gastropod shells or snail shells are typically shaped in a spiral.
- They have a single hole where the animal enters and exits the shell.
- Most of them are dextral (right-handed) shells, and some are sinistral (left-handed).
- Chitons (Scientific name: Polyplacophora), which are also called coat-of-mail shells, are usually flat and oval in shape with a dorsal shell that is made up of eight overlapped valves or plates.
- Underneath their plates are mantles encircled by a thick girdle or skirt, which may be covered with hair, scales, bristles, or spines.
- Chitons have organs unique to them that are called aesthetes, which act as the organism’s eyes.
- Tusk shells (Scientific name: Scaphopoda), which are also called tooth shells, are mollusks with an elongated, curved, tooth-like shell.
- Both ends of the shell are open, but one end can be closed.
- This species lives inside the tubular mantle and dig themselves into ocean floors.
- The anterior end of its body is typically buried in the ocean floor, while its posterior end is responsible for respiratory and secretion purposes.
BRACHIOPOD SHELLS
- Brachiopods are invertebrates with shells made up of two hinged valves.
- The upper and lower shells are of different shapes and sizes, but each shell’s right and left halves are symmetrical.
- They collect food using a special organ called a lophophore.
CRUSTACEAN SHELLS
- Crustaceans such as crab, lobster, crayfish, and shrimp have shells that consist mostly of chitin, a long-chain polysaccharide.
- The sugar-like polymers of chitin are made up of a derivative of glucose called acetylglucosamine.
- Aside from chitin, crustacean shells are also made up of protein and calcium carbonate.
- Crustacean shells are usually spiral in structure.
- Their shells do not grow, so they must undergo the process of molting or shedding their shells.
- The molts are called cast-off shells.
BARNACLE SHELLS
- Barnacles are also crustaceans, just like crabs, lobsters, and shrimp.
- However, they are not free-living; they are sessile or nonmobile creatures that must continually dwell in their shells.
- Also, as suspension feeders, barnacles cannot leave their shells to feed or mate.
- The shells of barnacles are made up of six calcium plates that completely encase them.
OTHER TYPES OF SHELLS
- A turtle’s shell primarily serves as a protective shield for its vital organs; both the ventral and dorsal parts of the turtle are covered.
- Both bones and cartilage make up a turtle shell.
- The dorsal (top) convex part is called a carapace, and the ventral (bottom), nearly flat part is called a plastron.
- The carapace and the plastron connect along the sides of the body.
- The shell is also covered in scutes, which are plates made of keratin that protect from scrapes and bruises.
- A turtle’s shell is also used to identify what species it is, especially when the turtle is fossilized.
- An eggshell is the outer covering of an egg which is made primarily of calcium carbonate.
- It is grainy in texture and is covered with thousands of pores.
- The pores make the eggshell semipermeable, meaning that certain substances like air and moisture can pass through it.
- Eggshells have a thin outermost coating called the bloom or cuticle which serves as an added protection from dust particles and bacteria.
- Because they are rich in calcium carbonate and other minerals such as potassium, magnesium, and phosphorus, eggshells make an effective fertilizer that aids plants’ growth.
USE OF SHELLS
- The hardness of shells makes them an effective protection for animals against predators, storms, and strong currents.
- For self-defense and protection, hermit crabs use discarded mollusk shells.
- As the hermit crab grows, it will look for larger shells to use for protection.
- Some animals also use their shells for camouflage.
- In commerce, humans can earn by selling shells as jewelry and adornments for clothing or household items.
- In ancient times, humans removed the living organisms from their shells so that they could use the shells as vessels for food and water.
- Shells were also once used as currency, coined “shell money”.
- The “money cowrie” (the shell of the sea snail Monetaria moneta) became the most widely used shell money worldwide.
CONCHOLOGY
- Conchology deals with the study and collection of marine, freshwater, and terrestrial shells.
- There are four main molluscan orders in conchology: bivalves (clams), gastropods (snail shells), Polyplacophora (chitons), and Scaphopoda (tusk shells).
- Bivalves are the most common type of mollusk shells that get washed up on seashores.
NON-MARINE SEASHELLS
- Non-marine “seashells” include tropical land snail shells, freshwater apple snail shells, and freshwater unionid mussel shells.
Shell Worksheets
This fantastic bundle includes everything you need to know about Shells across 27 in-depth pages. These ready-to-use worksheets are perfect for teaching kids about Shells. A shell is a hard, protective outer covering that has evolved in various marine animals, including mollusks and sea urchins.
Complete List of Included Worksheets
Below is a list of all the worksheets included in this document.
- Shells Facts
- Guess The Word
- Odd One Out
- Shell Sketching
- Spot The Shells
- Turning Them True
- A Unique Match
- Shell Bingo
- Uses of Shells
- Shell Idioms
- My Own Collection
Frequently Asked Questions
What are seashells?
Seashells are the hard, outer protective coverings or exoskeletons of marine animals. They are typically made of calcium carbonate and are formed by various marine organisms, including mollusks (such as snails, clams, and mussels) and certain types of crustaceans (such as crabs and lobsters).
How are seashells formed?
Seashells are formed through a process called biomineralization. Marine animals that possess shells have special cells in their bodies that secrete calcium carbonate, which hardens and forms the shell’s structure. Over time, the animal continues to deposit layers of calcium carbonate, gradually increasing the size of the shell as it grows.
Why do seashells have different shapes and patterns?
Seashells exhibit a wide variety of shapes, sizes, colors, and patterns. These characteristics are influenced by several factors, including the species of the animal that produced the shell, its habitat, and environmental conditions. The shape and pattern of a shell can provide protection, camouflage, or assist with locomotion and feeding strategies specific to the animal that inhabits it.
Where can seashells be found?
Seashells can be found in coastal areas around the world, particularly along shorelines and beaches. They are often deposited by ocean waves, tides, and currents, which carry shells from their original habitats to the shore. Some areas known for their abundance of seashells include tropical regions, coral reefs, and areas with diverse marine ecosystems.
Are seashells alive?
Seashells themselves are not alive, but they are the remains or external coverings of once-living marine organisms. After the animal inside the shell dies, the empty shell remains as a discarded structure. However, it’s important to note that some seashells may contain remnants of the animal’s tissues or be inhabited by other organisms, such as hermit crabs, which use empty shells for protection.
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Link will appear as Shell Facts & Worksheets: https://kidskonnect.com - KidsKonnect, February 17, 2008
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