Bones and Calcium

Abstract

Why is your grandmother always wondering if you are drinking enough milk? Our bones are made out of calcium, a mineral found in milk, and drinking milk can lead to strong healthy bones. What about other animals? What are their bones made of? What kind of bones do they have? Are there animals without bones? Are endoskeletons and exoskeletons made out of the same materials?

Objective

In this experiment you will explore the similarities and differences between bones and other hard parts from animals to determine which have properties similar to the calcium found in bones.

Introduction

Imagine what your body would be like without a skeleton. It would be too soft and squishy to stand up, and would not have the strength for walking or running. Our skeletons are very important for having large, muscular dynamic bodies that can move. Skeletons are important for a whole group of animals, called vertebrates, which like us have bones inside their bodies to support them.

Some of these vertebrates we like to eat: fish, chicken, beef and pork. Their bones are remarkably similar to ours, and are made out of the same mineral calcium. Calcium is important for other parts of the body as well, and vertebrates have found many ways to use calcium to build hard parts of the body like teeth or eggshells. All vertebrates use internal bony skeletons made out of calcium to support their bodies, but how do other animals support their bodies?

Other animals, called invertebrates, use many different strategies to support their body weight. Some invertebrates like earthworms have no hard body parts at all, and use a hydrostatic skeleton that supports the body using water pressure. Other invertebrates, like insects and crustaceans, have hard body parts on the outside of their bodies called an exoskeleton. A good example of this is a crab shell, a hard covering that both protects and supports the body of the crab. Other invertebrates make shells that partially enclose their body, like a snail shell. Some invertebrates, like sea urchins, even use their spiny skeletons for protection from predators.

What are these types of skeletons made of? Are bones and invertebrate exoskeletons made out of the same materials? One way to find out is to use another chemical that reacts with the calcium in bone to test if other hard body parts from other animals are also made out of calcium. You can use common household vinegar to react with the calcium found in bones. Will other animals have calcium in their hard parts too?

Terms, Concepts and Questions to Start Background Research

To do this type of experiment you should know what the following terms mean. Have an adult help you search the Internet, or take you to your local library to find out more!

• bone
• calcium
• skeleton
• endoskeleton
• exoskeleton
• vertebrate
• invertebrate
• mineralization
• calcification
• acid

Materials and Equipment

• vinegar
• cups
• hard parts of several different types of animals:
  • chicken bones
  • fish bones
  • egg
  • crab claw
  • shrimp shells
  • sea urchin test
  • tooth
  • snail shells
  • fingernail clippings

Experimental Procedure

1. Get several different types of materials to test from the hard parts from many different animal sources. Get as many different sources from as many different kinds of animals as you can. Use your imagination and the grocery store. Many grocery stores will give out soup bones for free.
2. Place each sample in a cup and label the cup with a description of the material.
3. Make initial observations of each sample. What does it feel like? What does it look like? Write down your observations in a data table, focusing on the similarities and differences between materials.
4. Pour vinegar into each cup until the sample is submerged, or covered, with vinegar.
5. Let your cups sit at room temperature for several days. Check the cups once in a while to be sure that the vinegar is still covering the material in the cup. You may need to add more vinegar to the cup if necessary.
6. Remove the samples from the vinegar and then observe the materials. How do they look and feel? How do the textures compare to before treatment with the vinegar?
7. Write down your observations in a data table, focusing on the similarities and differences between materials.
8. How do endoskeletons and exoskeletons compare? Did they react with the vinegar in a similar or different way? Do you think they are made out of similar or different materials?

Variations

• Bones are made out of calcium, which can be found in different forms in many vitamins and antacids. Try putting some calcium vitamins and different brands of antacids into a vinegar solution. Do they react similarly to the vinegar as bone?
• Some vertebrate bones have special adaptations. For example, the bones of birds are hollow to make them lighter for flight. Closely examine the bone of a chicken and you will notice tiny chambers in the middle of the bone. Chickens don't really fly, but they still have remnants of this type of bone structure. Examine the bones of some other birds from the store: turkey, quail, Cornish hen, goose or duck. What similarities do they all have? How are they different?
• One way to really clean off a skeleton is to boil the bones and then soak the skeleton in bleach. Try doing this with a quail, Cornish hen or small chicken. Can you put the skeleton back together?