Animal Shapes

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life sciences, language arts




life's diversity


one class period


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Before their visit, students will learn that... living things have different structures to support their bodies.

Background Information

Almost all animals have a skeleton [definition], the organ system that supports the body, provides shape and h elps animals move. But not all skeletal systems are similar. Some animals have a hard skeleton inside their bodies (e.g., the bones of fish, frogs, dogs and humans).

Other animals have hard skeletons on the outside (e.g., the cuticle of a grasshopper [graphic]), or produce a structure to protect the body (e.g., the shell of a clam). Some skeletons aren't hard, they're hydrostatic-- formed from sacs of fluid (e.g., in earthworms and sea anemones).

Skeletal systems are so important that scientists classify animals by their type of skeleton. Animals classified as vertebrate [definition] have internal skeletal systems made of bone [definition] or cartilage [definition]. Animals classified as invertebrate [definition] have solid, external skeletons or hydrostatic skeletons.

Because each species has a unique skeleton,you can use skeletal structure to identify animals. For example,you can tell a bird skeleton by its hollow bones. Features such as wing bone length and beak shape help you decide which species of bird the skeleton belonged to. Paleontologists identify fossils by examining skeletons and other hard parts such as shells left behind by once-living animals.

This activity gives your students a closer look at the structures that give animals shape and lets them compare the similarities and differences between vertebrates and invertebrates.



  • Pictures or mounted reproductions of whole animals. Invertebrates (animalswithout backbone [definition]) include: snail, giant squid, grasshopper, earthworm, starfish. Vertebrates (animals with backbones) include: frog, fish, bird and small mammal.
  • Prepared or fabricated snail shell, starfish test (body) and grasshopper cuticle.
  • Prepared or fabricated skeletons of frog, fish, bird and small mammal.


Touch your arm. What do you feel inside it?

(That's a bone. Bones make up your skeleton inside your body.)
Can you think of another animal that has a skeleton in its body?

Can you think of any animals that have skeletons outside their bodies?



  1. Place around the classroom pictures or mounted reproductions of whole animals. Use vertebrates and invertebrates (see list under Materials).
  2. Have your students walk around the room in pairs or small groups and sketch each specimen.
  3. Have them write (or discuss) their thoughts about each animal's skeleton. Do they think it's the same as their own skeletons or different?
  4. Bring the class back together.
  5. Using pictures or fabricated shells and skeletons, discuss each specimen, emphasizing the differences between the skeletal systems of vertebrates and invertebrates.


What do you think you would be like without your skeleton?
How does a skeleton help an animal?

Adapted from

Science: Model Curriculum Guide, Kindergarten Through Grade Eight. Sacramento: California State Department of Education, 1987.

Additional Sources

Arms, Karen and Pamela 5. Camp. Biology. Philadelphia: Saunders College Publishing, 1987. Burnie, David. How Nature Works. Pleasantville, NY: Reader's Digest Association, Inc., 1991.