Introduction: (Initial Observation)
We know egg as a nutritious food and as source of producing chicken. But what is inside the egg? How can it produce chicken? Can all eggs hatch to chicken?
Although we have all seen eggs, we may not exactly know about the structure or parts of the egg. An egg display project is an opportunity to learn more details about egg and eggs parts.
Your display must be interesting and educational for others who see your project.
Warning:
Any cutting or handling sharp objects in this project must be done by adults.
Information Gathering:
Find out about egg parts. Read books, magazines or ask professionals who might know in order to learn about egg as a nutritious food and as an important stage in chickens life. Keep track of where you got your information from.
Following are samples of information that you may gather and use for your display project.
Contrary to popular opinion, the chicken does not lay eggs with the sole purpose of providing humans with breakfast. Once the hen has laid a certain number of eggs, she starts to “brood.” For 21 days, she just sits there, keeping her eggs warm as the chicks develop inside them.
“If you could look inside the egg about 7 to 10 days before hatching, you’d see a tiny embryo and a yellow yolk surrounded by a watery liquid. The yolk provides food for the embryo as it grows into a bird.”
A hen’s egg is nature’s way of reproducing the species and contains all the essential nutrients for life. All the required nutrients are packed into the yolk and albumen (egg white) before it is laid, since the egg is a sealed unit. A fertile egg must contain the exact amount of water, protein, carbohydrates, minerals, vitamins and fats which are needed, since any deficiency will reduce the embryo’s ability to grow, hatch and survive.
Egg Parts
SHELL Bumpy and grainy in texture, an eggshell is covered with as many as 17,000 tiny pores. Eggshell is made almost entirely of calcium carbonate (CaCO3) crystals. It is a semi permeable membrane, which means that air and moisture can pass through its pores. The shell also has a thin outermost coating called the bloom or cuticle that helps keep out bacteria and dust.
INNER AND OUTER MEMBRANES Lying between the eggshell and egg white, these two transparent protein membranes provide efficient defense against bacterial invasion. If you give these layers a tug, you’ll find they’re surprisingly strong. They’re made partly of keratin, a protein that’s also in human hair.
AIR CELL
An air space forms when the contents of the egg cool and contract after the egg is laid. The air cell usually rests between the outer and inner membranes at the egg’s larger end, and it accounts for the crater you often see at the end of a hard-cooked egg. The air cell grows larger as an egg ages.
ALBUMEN
The egg white is known as the albumen, which comes from albus, the Latin word for “white.” Four alternating layers of thick and thin albumen contain approximately 40 different proteins, the main components of the egg white in addition to water.
CHALAZAE Opaque ropes of egg white, the chalazae hold the yolk in the center of the egg. Like little anchors, they attach the yolk’s casing to the membrane lining the eggshell. The more prominent they are, the fresher the egg.
VITELLINE
MEMBRANE The clear casing that encloses the yolk.
YOLK
The yolk contains less water and more protein than the white, some fat, and most of the vitamins and minerals of the egg. These include iron, vitamin A, vitamin D, phosphorus, calcium, thiamine, and riboflavin. The yolk is also a source of lecithin, an effective emulsifier. Yolk color ranges from just a hint of yellow to a magnificent deep orange, according to the feed and breed of the hen.
| What is missing in the egg diagram that you see in the right?If you answered air cell, you are right. Air cell is an important part of the egg and must be in the blunt side of the egg. |
How does the egg form inside the hen’s body?
The delicate structures of the egg are ‘assembled’ in four precise stages:
- First the yolk and ovum develop in the ovary, among a ‘grape-like’ cluster of similar ovules, or miniature yolks. The yolk, together with its unfertilized blastoderm, (the ovum), matures in the ovary until it is released into the ‘infundibulum’ (the upper funnel) of the oviduct, where it encounters the male sperm and is fertilized.
- The fertilized egg with its microscopic embryo now passes down to the ‘magnum’ (the upper middle section of the oviduct), where a layer of watery albumen (the egg-white) envelops the yolk in a thin sack. At opposite ends of the yolk, thin strands of albumen become twisted to form the rope-like ‘chalaza’; these two cords suspend the yolk centrally in a floating ‘hammock’ as it travels down the oviduct; the chalaza prevent the yolk from rising to bruise itself against the shell membranes. Before the yolk leaves the ‘magnum’ the remaining volume of watery albumen is wrapped around it.
- The developing egg then enters the ‘isthmus’ (the lower mid-section of the oviduct) where the yolk and albumen are completely encapsulated in two loose-fitting shell membranes.
- The egg then passes on to the ‘uterus’, where the final stage of egg formation occurs. About 80% of the egg’s development is spent in the uterus; here the shell membranes tighten around the yolk and albumen, and the outer eggshell is finally secreted.
Once the shell has hardened, the finished egg passes down to the cloaca and is laid. This whole process takes about 24 hours.
The hen lays one egg per day, until she has a clutch of 3 to 6 eggs, depending on the breed of canary. She then incubates them for 13 days, and our ‘small treasures’ hatch into the next generation of “show winners”!
* Chalaza or Chalazae is one of two spiral bands of tissue in an egg that connect the yolk to the lining membrane at either end of the shell.
COMMON QUESTIONS ABOUT EGG
Q: WHAT CAUSES BLOOD SPOTS?
A: Small spots of blood (sometimes called “meat” spots) are occasionally found in an egg yolk. These do not indicate a fertile egg; they are caused by the rupture of a blood vessel on the yolk surface during formation of the egg. Most eggs with blood spots are removed during the grading process but a few may escape detection. As an egg ages, water moves from the albumen into the yolk, diluting the blood spot. Thus, a visible blood spot actually indicates a fresh egg. Such eggs are suitable for consumption. The spot can be removed with the tip of a knife, if you wish.
Q: WHY DO SOME HARD-COOKED EGGS HAVE A GREENISH RING AROUND THE YOLK?
A: The harmless greenish ring is due to an iron and sulfur compound which forms when eggs are overcooked or not cooled quickly.
Q: IS THERE A DIFFERENCE BETWEEN BROWN AND WHITE SHELLED EGGS?
A: No. Shell color is determined by the breed of hen and is not related to quality, nutrients, flavor or cooking characteristics. Since brown egg layers are slightly larger birds and require more food, brown eggs are usually more expensive than white.
Q: HOW LONG WILL EGGS KEEP?
A: Fresh shell eggs can be kept refrigerated in their carton for at least 4 – 5 weeks beyond the pack date. Quality losses should be insignificant if the eggs are refrigerated as soon as possible after purchase from a refrigerated case.
Hard cooked eggs should be kept in the refrigerator for up to one week.
Q: WHAT IS THE BEST WAY TO STORE EGGS?
A: Store eggs in their carton because eggs can absorb refrigerator odors.
Q: IS IT SAFE TO EAT RAW EGGS?
A: The risk of food poisoning from eggs is highest with raw and lightly-cooked dishes. It’s best not to serve raw or lightly-cooked dishes made with eggs.
Q: WHAT ARE THE STRINGY WHITE PIECES IN EGG WHITES?
A: These rope-like strands of egg white, called chalazae (ka-LAY-zee) are not imperfections or beginning embryos but a natural, edible part of the egg. They keep the yolk centered in the thick white.
Q: ARE EGGS AN ECONOMICAL FOOD?
A: Eggs are one of today’s best food buys. A dozen Large eggs weighs 1 ½ pounds so at 90¢ a dozen, eggs are only 60¢ per pound. Eggs supply high-quality protein and a variety of important vitamins and minerals at a very low price.
Q: ARE FERTILE EGGS MORE NUTRITIOUS?
A: Fertile eggs are not more nutritious than nonfertile eggs. They do not keep as well as nonfertile eggs and are more expensive to produce.
Q: WHY ARE SOME HARD-COOKED EGGS DIFFICULT TO PEEL?
A: Fresh eggs may be difficult to peel. Those which have been stored for a week to 10 days before cooking will usually peel more easily.
Q: WHY IS AN EGG WHITE SOMETIMES CLOUDY OR HAS A YELLOW OR GREENISH CAST TO IT?
A: Cloudiness of raw white is due to the presence of carbon dioxide which has not had time to escape through the shell and is an indication of a very fresh egg. A slight yellow or greenish cast in raw white may indicate the presence of riboflavin.
Question/ Purpose:
What do you want to find out? Write a statement that describes what you want to do. Use your observations and questions to write the statement.
The purpose of this project is to display the parts of the egg.
A display project does not require specific questions; however, following are some sample questions related to eggs.
- How do you know if an egg is fresh or not?
- How can you identify a hard boiled egg among some fresh eggs?
Identify Variables:
When you think you know what variables may be involved, think about ways to change one at a time. If you change more than one at a time, you will not know what variable is causing your observation. Sometimes variables are linked and work together to cause something. At first, try to choose variables that you think act independently of each other.
Not required for this project.
Hypothesis:
Based on your gathered information, make an educated guess about what types of things affect the system you are working with. Identifying variables is necessary before you can make a hypothesis.
Not required for display projects.
Experiment Design:
Design an experiment to test each hypothesis. Make a step-by-step list of what you will do to answer each question. This list is called an experimental procedure. For an experiment to give answers you can trust, it must have a “control.” A control is an additional experimental trial or run. It is a separate experiment, done exactly like the others. The only difference is that no experimental variables are changed. A control is a neutral “reference point” for comparison that allows you to see what changing a variable does by comparing it to not changing anything. Dependable controls are sometimes very hard to develop. They can be the hardest part of a project. Without a control you cannot be sure that changing the variable causes your observations. A series of experiments that includes a control is called a “controlled experiment.”
Experiment 1:
Make a model of the egg to show the main parts of the egg including the shell, membrane, yolk, air cell, chalazae and egg white (albumen). You may choose to make a large scale drawing of the following diagram; however I recommend to make a 3 dimensional model of the egg as described below.
There are many different ways that you can make a 3D model of an egg.
Procedure 1:
Get an oval shape bowel. Place a thin layer of plastic film on that and fill it up with colorless or light color gelatin (Jell-O). The bowel will be the shell, the thin plastic film is the membrane, the gel is the egg white. Before the gel hardens, place a yellow ball in the center of bowel. Half of the yellow ball must be in the gel. After the gel hardens (in the refrigerator), carefully cut and remove a piece of gel from one end of the bowel to simulate the air sack (air cell). Use some food coloring or water color to draw chalazae on both sides of the yolk (yellow ball). Also use water color or marker to put one dot on the yolk to represent the germinal disk. Your egg model is ready for display.
Additional notes: You can use a lemon or peach as the yolk. You can also use honey or jam to draw the chalazae. If you avoid using paint, ink and other hazardous material, your final display will be eatable.
Procedure 2:
Use balls and egg shape Styrofoam pieces to make a 3D model of an egg.
Styrofoam blocks, balls, sheets and egg shape pieces can be purchased from many craft stores. They can also be ordered by mail from MiniScience.com. Get one large egg shape piece and one ball shape piece of Styrofoam. The with of the Styrofoam ball that you select must be about half of the width of the egg foam.
Use a hack saw or utility knife to cut the foams in half. Each half can be used for one model of egg.
On the blunt end of the egg shape foam cut a deep space to simulate the air cell. Then paint the entire foam with white latex paint. This layer of paint is just the base, that is why you paint both the half egg and the half ball.
Let the paint dry in about 5 hours.
Then start to the final paint or decorative paint. The half ball must be painted with yellow latex or any other water base paint.
Use light brown for the egg shell. Every thing else depends on your creativity.
A final egg model may look like this. If you also have a large drawing of the egg parts, your model is ready. If you don’t have a drawing (similar to the diagram that you see above), you will need to write the name of egg parts on small labels and attach them to your model where they belong.
Even if you have a diagram, it is still a good thing to label egg parts on your model.
Experiment 2:
How can you know about inside the egg without breaking it
Fresh eggs often get mixed with older eggs in the fridge, so how do you tell whether your eggs are fresh? As the egg ages, its air sack increases in size. This will make the blunt end of the egg lighter. This change can help us to determine if an egg is aged or stale without breaking it.
Procedure:
Get 3 fresh eggs and place them in a bowel of water. Record your observation. (All three eggs must sink and lie flat on the bottom of water.)
Remove the eggs from the water and keep them out of the refrigerator in different parts of the house with different temperatures. It is best if you place each egg in a small plastic container and label the container with cold, normal or warm depending on the place that you keep them.
After 7 days place the eggs in the bowel of water again (one at a time) and record your observation.
Place the eggs back in their container and wait another 7 days. You may need to repeat this cycle for four weeks until you have at least one stale egg that float on the water.
Conclusion:
To find out if eggs are fresh or not, we can place them in a bowl of water. Fresh eggs should lie flat on the bottom of the bowl like the egg on the left…
As the egg ages, its air sack increases in size and, in a bowl of water, the egg will gradually stand upright and, eventually after about three weeks, look like the egg on the right. When it is stale, it will float.
Eggs that spring into the upright position in a bowl of water are edible but no longer fresh – once they become buoyant, save them for throwing at undesirables.
Experiment 3:
How do you find out whether or not an egg is fresh or hard boiled?
Procedure:
Check to see whether or not an egg is fresh or hard boiled by spinning it on its side…
…while it is spinning, put your finger on top of it just long enough to stop it spinning. Then immediately remove your finger…
…if the egg is fresh, it will start to spin again. If it is hard boiled, it will remain still.
Prepare a display
A display board on egg parts project must include the following information. You may type these with large font and print them by computer. You may also decide to write them by hand. In both case these writings will be on individual papers and you connect them to your board by pin or tape. Do not write directly on your display board.
SHELL
- the first line of defense against the entry of bacteria
- can be brown or white; nutritional value of the egg is the same
- composed mainly of calcium carbonate
- approximately 8,000 to 10,000 tiny pores allow moisture and gases in (O2) and out (CO2)
SHELL MEMBRANES
- there are two membranes on the inside of the shell
- one membrane sticks to the shell and one surrounds the white (albumen)
- the second line of defense against bacteria
- composed of thin layers of protein fibers
GERMINAL DISC
- appears as a slight depression on the surface of the yolk
- the entry for the fertilization of the egg
WHITE (ALBUMEN)
- there are two layers: thin and thick albumen
- mostly made of water, high quality protein and some minerals
- represents 2/3 of the egg’s weight (without shell)
- when a fresh egg is broken, the thick albumen stands up firmly around the yolk
CHALAZA
- a pair of spiral bands that anchor the yolk in the center of the thick albumen
- the fresher the egg the more prominent the chalazas
- unnoticeable when the egg is cooked
YOLK MEMBRANE
(VITELLINE MEMBRANE)
- surrounds and holds the yolk
- the fresher the egg the stronger the membrane
YOLK
- the egg’s major source of vitamins and minerals, including protein and essential fatty acids
- represents 1/3 of the egg’s weight (without shell)
- yolk color ranges from light yellow to deep orange, depending on the hen’s food
AIR CELL
- forms at the wide end of the egg as it cools after being laid
- the fresher the egg the smaller the air cell
Materials and Equipment:
List of material can be extracted from the experiment section.
Results of Experiment (Observation):
Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. A series of experiments is made up of separate experimental “runs.” During each run you make a measurement of how much the variable affected the system under study. For each run, a different amount of change in the variable is used. This produces a different amount of response in the system. You measure this response, or record data, in a table for this purpose. This is considered “raw data” since it has not been processed or interpreted yet. When raw data gets processed mathematically, for example, it becomes results.
For the first experiment, the model that you make is the result. For other experiments, your observation is your results.
Calculations:
No calculation is required.
Summary of Results:
Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.
It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.
Conclusion:
Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.
Related Questions & Answers:
What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested.
Possible Errors:
If you did not observe anything different than what happened with your control, the variable you changed may not affect the system you are investigating. If you did not observe a consistent, reproducible trend in your series of experimental runs there may be experimental errors affecting your results. The first thing to check is how you are making your measurements. Is the measurement method questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe the measuring instrument is working erratically.
If you determine that experimental errors are influencing your results, carefully rethink the design of your experiments. Review each step of the procedure to find sources of potential errors. If possible, have a scientist review the procedure with you. Sometimes the designer of an experiment can miss the obvious.
References:
List of References
http://www.wsu.edu/DrUniverse/eggs4.html
