Guest post by Erin Votaw, GSC Educator
If you aren’t familiar with Nature Tots programs at the Greensboro Science Center, let me introduce myself. My name is Erin and I am a part of the Education department here at the Greensboro Science Center. I have been teaching Nature Tots classes, summer camps and grant programs for the past 10 years. I thought it may be fun to investigate some of the topics we didn’t get to meet up for in our Nature Tots class. We always have such a fun time together on Tuesdays and I look forward to the time when we get back to the fun, together in our special place with visiting animals and keeper talks. The GSC is working hard to keep the animals happy but I know they miss seeing your sweet faces checking on them.
Hello again, my preschool science buddies! I am excited to be back with you for another adventure. Let’s get busy! Spring is in the air and the temperatures, trees, flowers and animals are making changes. One of the most popular activities around this time of year is talking about eggs. Do you know which animals are oviparous?
Oviparous is certainly a big science word that we don’t hear very often. It is the type of word that helps scientists classify animals into groups for ease of learning. Kind of like herbivore and carnivore (remember those words from talking about the dinosaurs?). Same deal here, just not used as often. Oviparous helps us know that group is together because those animals have their offspring by laying eggs. Can you think of animals that lay eggs? Most fish, reptiles and all birds are oviparous. Less than 2% of fish (goldfish, for example) and 20% of reptiles (boa snakes, for example) have live births of their offspring – no egg is laid, so they are not oviparous, but viviparous (have live young). This could be a result of where they live in the world.
There are only two mammals that lay eggs, all other mammals give birth to live young that are either dependent upon mom for everything or are ready to go on their own. The echidna and duck-billed platypus of Australia are the only mammals that lay eggs.
There is a really sweet book that is well illustrated about oviparous animals called “Chickens aren’t the only ones” by Ruth Heller. The story talks about chickens and other birds, reptiles, insects, fish, amphibians and even the mammals that are exceptions to the rule with a rhyming flow and beautiful illustrations.
Now that you know what an oviparous animal is, let’s investigate and learn more. Each animal’s egg comes with its own characteristics that can be different. These can include size, colors, shapes and even shell texture! Not surprisingly, the largest egg comes from the ostrich, followed by the emu and rhea. The smallest egg comes from the smallest bird. Anyone? The hummingbird!
We are also familiar with turkey and chicken eggs that we see more frequently.
We also can recognize the cardinal (North Carolina state bird) and bluebird eggs based on their coloring. Maybe you have seen these eggs in your yard recently.
What is going on inside that egg? There are some different parts that play important roles in the egg’s development. When we look at an egg, we notice the outer shell. It may be bumpy or smooth and dark or light in color, but the egg shell is critical to the animal for a couple of reasons. We know what happens when we drop an egg right? Oops! Egg shells are made of calcium carbonate which is similar to the calcium phosphate that make up our teeth. If we gently tap our teeth with our fingernails, you may hear a click sound similar to that if you did it to an eggs shell. Strong enough to be protective, but still thin enough to allow air to pass through. Wow, eggs can breathe!
Experiment: Bouncy Egg
Because of that calcium carbonate of the egg shell we can use science to make the egg rubbery and almost bouncy like a ball! Also, I have a bunch of hard boiled eggs left over from Easter so I thought this would be fun to play with as well. And my favorite color is blue, so that is why I picked my blue Easter egg! Take one of your hard boiled eggs and put it in a clear glass of vinegar overnight (up to a week changing the vinegar every couple days you will completely remove the shell almost making it translucent).
Keep checking on the egg in the vinegar and look for any activity or changes. Little bubbles may come off the egg as the acetic acid in the vinegar attacks the calcium carbonate of the eggshell. Over time, the color of the eggs may change as well. The next day or later, get the egg out of the vinegar and investigate. Shine a flashlight through the egg. What does it look like compared to a regular egg shell? What does the egg smell like now? Feel like? Move like? Weird, right? Where did the hard outer shell go and how did it change? You may have actually dissolved the calcium carbonate (what makes the shell stiff), leaving behind the permeable part of the shell making it now rubbery and bouncy. How high can you bounce your rubbery egg?????
WATCH: Rubber Egg Bounce
Experiment: Egg in a Bottle
Another cool trick is to fit an egg into a bottle. When you first look at this you think, Miss Erin, there is no way that egg can get inside that bottle! But wait, I say….Science!!!
- First peel your hard-boiled egg.
- Next, with the help of an adult, set a small piece of paper on fire and drop it into the bottle.
- Before the fire goes out, set the egg on top of the bottle, small side pointed downward.
As the temperature inside the bottle changes, air pushes the egg into the bottle! Magic!!! How did that happen? Why science my darlings, of course. But seriously, the answer has to do with the air pressure inside the bottle. You changed the temperature inside the bottle and that caused the air to rush inside the bottle, taking the egg with it!
WATCH: Egg in a Bottle
Getting the egg out should work with the opposite right? Can you think of how to get “outside” air back into the bottle? While holding the jar upside down and the egg is in the opening of the bottle, try using a straw to put “outside” air back inside the bottle to help re-balance the air pressure. By blowing into the straw, you can create pressure inside the bottle that will make the air want to move out – and when it does, it’ll take the egg with it!
I hope to bring you more blogs and activities to help keep you engaged in our science world. Be on the lookout for more content from Greensboro Science Center behind the scenes, keep talks, activities and adventures for all to enjoy! I hope to see you again soon, until then have fun and remember science is everywhere!