The embryos inside the eggs can breathe by using the air sac, which is a small cavity of air present inside the egg. Additionally, there are pores in the eggshell that allow gases to enter and escape the egg, enabling gaseous exchange.
Similar to humans, animal babies that grow inside their mothers receive all the necessary resources for development through an umbilical cord that collects oxygen and other nourishment from the mother. However, for animals like chickens that grow inside an egg, the process is not as straightforward. Since the egg does not have any visible holes or openings, it is completely isolated from the outside world. This raises the question of how the developing bird inside gets the crucial oxygen it needs for vital biochemical functions.
How do the baby birds survive inside these eggs? (Image Source: Wikimedia Commons)
Furthermore, when oxygen is used to produce energy, it generates carbon dioxide as a byproduct. It is well-known that excessive carbon dioxide in a sealed space can be dangerous and even fatal to the inhabitant. So, how is the carbon dioxide eliminated from the egg?
Gaseous Exchange Through the ‘Air Sac’
An egg is a remarkable example of how nature takes care of its creatures. The structure of an egg not only protects the developing chick but also fulfills its basic biological needs until it is ready to hatch. Here’s how it works: there are two membranes beneath the chicken’s egg. When the mother lays the egg, it is warmer than the surrounding air.
The air cell in an egg provides oxygen to the developing bird
Naturally, as the egg begins to cool, the material inside contracts slightly, creating a small gap between the two membranes. This separation forms an ‘air sac’ that contains an ample supply of oxygen.
Egg Shells Have Pores for Gaseous Exchange
The air sac can only hold a limited amount of oxygen, so it needs to be replenished. Additionally, the carbon dioxide produced by the chick must be removed from the egg. How does this happen?
Exactly! The exchange of gases occurs through diffusion. Egg shells have numerous tiny pores on their surface. For instance, a 60-gram chicken egg has around 10,000 pores that facilitate diffusion through the shell!
An egg has plenty of pores to allow gas and water exchange
During the chick’s development, the oxygen from the air sac is consumed, and carbon dioxide takes its place. However, through diffusion across the thousands of pores on the eggshell, carbon dioxide escapes the egg, and fresh oxygen from the surroundings is supplied to the developing bird. These pores also play a crucial role in water exchange.
Inside an egg, a chick can survive by going through various processes until it hatches. Different avian species have their young ones growing inside eggs, and while there may be some differences between species, such as ostrich eggs being larger and less efficient in exchange, the overall processes remain the same.
Here are a few interesting facts about eggs:
1. The color of the yolk depends on the hen’s diet. If it consumes orange and yellow plant pigments, the egg’s color will be more vibrant.
2. The aging rate of eggs is affected by temperature conditions. An egg ages faster at room temperature in one day than it does in one week inside a refrigerator.
3. The size of an egg indicates the age of the hen that laid it. Young hens lay smaller eggs, but as they age, the egg size increases.