Try This: Animal Camouflage
If you know someone who has been trained in the military, you might have seen them in uniforms called fatigues. Sometimes they are called camouflage because these uniforms make it difficult for others to see the wearers when they are in hiding. But some animals, like the chameleon, do this naturally and serve as models for how to do it right.
QUESTION
How do animals blend into their surroundings?
MATERIALS
2 large sheets of construction paper in each of three different colors
Scissors
A partner
PROCEDURE
Cut one sheet of each color into 2-inch by 2-inch squares.
Place all of the colored squares onto one of the large sheets while your partner closes his eyes.
When your partner opens his eyes, give him five seconds to grab as many colored squares as he can.
WHAT'S HAPPENING
Our eyes quickly notice sharp contrasts in color. You partner will usually pick out squares that are not the same color as the sheet they are lying on. When animals (and humans) use camouflage, they are taking advantage of the fact that when their colors match those around them (green frogs in grass, brown lizards on a tree branch) predators don't see any contrast, and the animals are somewhat hidden. If you placed a brown frog in the grass or a green lizard on a tree branch, that animal would stand out and would not be protected.
FOLLOW-UP
If you know someone who owns sunglasses called Blue Blockers, ask if you can try them on. When you do, what colors do you see most strongly? Do you know why this is?3
Eye Spy
Can you find the 10 creatures hiding in this picture?
QUESTION Why are eggs shaped the way they are?
EXPERIMENT OVERVIEW You will be exploring the shapes of eggs and the incredible strength they possess despite their fragile structure. By carefully preparing the eggs, you'll be able to place several books on top of four half-shells without cracking the shells. As a follow-up, you'll get to consider other versions of this test.
SCIENCE CONCEPT Eggs are shaped the way they are for many reasons. A simple one is that the egg shape doesn't roll well. As a result, if a mother is sitting on her eggs and one gets away from her, it won't roll far before it comes to a stop. This allows the mother to quickly retrieve it. Try this before you begin the experiment. Gently roll an egg across the table or counter. Notice how its unique shape prevents it from rolling far like a ball would.
Another reason for an egg's shape is that the dome shape gives it more strength than almost any other shape. Some people can place an egg in the palm of their hand and squeeze as hard as they can and not break the egg. The force of the hand is spread over the entire surface of the egg and nowhere is the force great enough to cause the egg to break. If you want to try this, you should either do it outside or in a large sink, for if you don't hold the egg just right, it will explode all over you!
MATERIALS
At least 4 raw eggs
Masking tape
Small scissors
Several books approximately the same size
PROCEDURE
Gently crack the eggs and break the shells as near to the middle (horizontally) as you can. If you don't get a good break, you'll need to try another egg.
Pour the raw eggs into a bowl and fry them up for your family.
Rinse and dry the empty half-shells.
Place one strip of tape around the open end of each shell, leaving the jagged edge exposed.
Use the scissors to trim off the jagged edges, taking care not to break the remaining shell.
You should now have four rounded egg bottoms and four pointed egg tops.
Select the rounded bottoms and place them in a rectangle on a table, approximately where the corners of your books will be.
Predict how many books your eggs will hold.
Gently add books until cracks first appear. This is the point when it becomes important that the egg supports are all about the same size. Note how many books caused the eggs to crack the first time.
Continue adding books until the eggs collapse.
QUESTIONS FOR THE SCIENTIST
Did your eggs hold more or less books than you predicted?_______________________
Why do you think the eggs can hold so much weight when they can be broken so easily on the side of a mixing bowl?______________________________________________
What changes could you make to this experiment so that, still using eggshells, even more books could be supported?___________________________________
FOLLOW-UP Try using the pointed ends of the eggs and repeating the experiment. Which end of the eggshell held more weight? Think about the magicians who lie on beds of nails. How does this experiment explain the “trick”? Think about the use of snowshoes in lands where a large amount of snow falls. Do these walking aids have anything to do with your egg experiment?4
