We are finding so many ways to sort and graph our eggs. This time we looked at which one have soft shells and which have hard shells. We were able to make the generalizations that bird and insect eggs tend to have hard shells while reptile and amphibian eggs have soft shells. Amphibians tend to have a jelly-like substance surrround the eggs.
We also talked about the different shapes of the eggs. The elongated shape of the eggs help the parent to turn the eggs while incubating them to keep them warm. The pear-shaped eggs laid by birds like the murre, pivot in a circle so that it is less apt to roll. The eggs that are not turned during incubation tend to be more rounded.
We talked about how shape can affect how an object moves. We set up a ramp and rolled a round ball down it and saw that it rolled fairly straight, perhaps curving slightly toward the end of its roll, but generally straight.
Then we rolled the plastic eggs down the ramp and could see that it distinctly curved in its path.
We then talked about how birds turn their eggs a dozen times an hour and that the oval shape makes it easier for them to turn the eggs. If the egg does roll, it rolls in a circular pattern, just like the plastic egg did on their ramp, making it head back to its starting point.
I then asked them which way it curved and they rolled more eggs and concluded that it rolled toward it's more pointed end. We talked about how the Murre uses no nest materals by lays its one egg on the ledge of a cliff near the ocean. The eggs has an even more elongaged oval with a thinner pointed end than the chicken egg we are used to seeing. Because it is so thin on its end, it rolls in a sharper circle and this keeps it from rolling off the cliff. Murre Eggs are interesting in another way as well. They come in many colors and patterns so that the parent bird can recognize their own egg among all the eggs on the cliff that don't have nests to keep them seperate.