Eggs

Ostrich, Cassowary, and Emu eggs

Photos by Graham Mitchell-Lawson and Kim Chapman.
The Royal Alberta Museum, E.T. Jones collection.

© 2006 Government of Alberta and © 1996-2006 Royal Alberta Museum.


Eggshells vary widely in surface texture. Most eggs are smooth but some, like those of the Cormorant, can be quite rough. As well, eggs of cormorants are chalky, rather than shiny, as in tinamous. Duck eggs are oily and waterproof, and cassowary eggs are very heavily pitted.
Eggshells vary widely in surface texture. Most eggs are smooth but some, like those of the Cormorant, can be quite rough. As well, eggs of cormorants are chalky, rather than shiny, as in tinamous. Duck eggs are oily and waterproof, and cassowary eggs are very heavily pitted.

© 2006 Government of Alberta and © 1996-2006 Royal Alberta Museum.

Eggshells

Eggs can be rough, like these Cormorant eggs, or shiny and smooth like these Tinamou eggs.

Photos by Graham Mitchell-Lawson and Kim Chapman.
The Royal Alberta Museum, E.T. Jones collection.

© 2006 Government of Alberta and © 1996-2006 Royal Alberta Museum.


Regardless of how smooth an egg may feel, all eggshells have tiny holes or pores. The domestic hen’s egg, for example, may have 7500 pores. Most of these pores are at the blunt end of the egg. Pores connect the egg with its surroundings. Respiratory gases as well as water vapour travel through these channels and enable the egg to breathe.
Regardless of how smooth an egg may feel, all eggshells have tiny holes or pores. The domestic hen’s egg, for example, may have 7500 pores. Most of these pores are at the blunt end of the egg. Pores connect the egg with its surroundings. Respiratory gases as well as water vapour travel through these channels and enable the egg to breathe.

© 2006 Government of Alberta and © 1996-2006 Royal Alberta Museum.

We normally think of eggshells as being very fragile. However, eggshells are remarkably strong and durable. They provide the embryo with good protection from predators as well as from soil invertebrates and harmful bacteria. The shells of eggs that we eat from the domestic hen are thinner and more fragile than those of its ancestor, the Red Junglefowl. The thinning has occurred because chickens have been bred to produce larger eggs with the same amount of shell material. The resulting egg would not likely survive incubation in the wild.
We normally think of eggshells as being very fragile. However, eggshells are remarkably strong and durable. They provide the embryo with good protection from predators as well as from soil invertebrates and harmful bacteria. The shells of eggs that we eat from the domestic hen are thinner and more fragile than those of its ancestor, the Red Junglefowl. The thinning has occurred because chickens have been bred to produce larger eggs with the same amount of shell material. The resulting egg would not likely survive incubation in the wild.

© 2006 Government of Alberta and © 1996-2006 Royal Alberta Museum.

Eggshells are made of calcium and magnesium salts within a fibrous network. Calcite is the main salt used as building material for the shell. As the embryo develops, calcium is transferred from the shell to the growing bones of the embryo. After a chick hatches, the mother sometimes eats the shell to recover some of the calcium lost in the making of an egg.
Eggshells are made of calcium and magnesium salts within a fibrous network. Calcite is the main salt used as building material for the shell. As the embryo develops, calcium is transferred from the shell to the growing bones of the embryo. After a chick hatches, the mother sometimes eats the shell to recover some of the calcium lost in the making of an egg.

© 2006 Government of Alberta and © 1996-2006 Royal Alberta Museum.

The outer surface of the eggshell is covered by the cuticle. The cuticle is a thin layer made of proteins. The cuticle adds strength to the shell, gives the shell its texture and provides a barrier against bacteria.
The outer surface of the eggshell is covered by the cuticle. The cuticle is a thin layer made of proteins. The cuticle adds strength to the shell, gives the shell its texture and provides a barrier against bacteria.

© 2006 Government of Alberta and © 1996-2006 Royal Alberta Museum.

Learning Objectives

The learner will:

  • Become familiar with the basic biology of eggs, and their variation
  • Relate ecology to evolution and adaptation (relate form and function)

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