Egg

The egg is an early stage of self- development ( ontogeny ) of a hurry ing animal ( Ovipars ). It contains in addition to the nucleus, also called egg, nutrients, and a protective shell ( " bowl "). The internal structure of the ice is divided into various functional structures.

Eggs are a popular food due to their high nutritional value. In response to numerous strategies to protect the ice and thus to improve the survivability of the species have developed.

Principle of Operation

An egg is a closed system through its hull, within certain limits and offers the evolving creatures for a limited time a shelter. This room is located at the beginning of a depot of substances that provide energy and body mass. The stage of the egg is terminated by the hatching, usually when the vault is almost completely consumed by living organisms.

Egg membrane

In the simplest case, in many original marine animals, consists only of the egg the egg. Most of these, however, protected by a deposited by the mother gelatinous sheath or shell. In terrestrial animals, the shell still satisfied in addition to the mechanical protection of the important function of protecting the egg against dehydration. The shell eggs of insects is often conspicuously sculptured, so you can determine the species of insects at this stage. For independent from the water terrestrial vertebrates, the amniotes ( reptiles, birds and Ursäuger ), is located between egg shell and another introduced by the mother layer the egg whites (see bird's egg ).

Yolk

Add the egg at special points embedded nutrients are referred to as yolk. With many original water animals will hatch after a short time a tiny larva, which feeds automatically, leaving little yolk must be present in the oocyte. Such eggs are called dotterarm or oligolecithal. Among the vertebrates put the most fish and amphibian yolk- poor eggs.

For eggs, which hatch already well developed young animals, the egg is very large and consists mostly of yolk. These yolk-rich eggs or polylecithalen the first cell divisions, furrowing differ called, clearly the conditions in yolk- poor eggs. More in Article egg.

Egg shape

Since eggs as a resting stage have no external organs such as limbs or fins, mouthparts and sensory organs, they are easily formed, usually the longitudinal section is an oval. The variations range from the common spherical shape to rounded at the ends of the cylinder ( "pen" ) as it is widely found in insects, and almost conical Lummenei. However, some eggs have external appendages serve to fasten; best known, this is in the eggs of the Real skate.

Oviposition and brood care

In the most primitive case, especially for fixed ( sessile ) animals that unfertilized eggs and sperm are released into the water easily. Moving water animals lay eggs mostly at particularly suitable places from, so put trout fish for spawning in gravel redds on special, toads wrap cords around their spawning aquatic plants. The survival of the eggs can be increased by parental care, such as guarding the eggs of fish species such as sticklebacks and the incubation in birds. In extreme cases, the eggs are hatched in the womb, such as ovoviviparous sharks and rays or viviparous tooth carp, but also in various invertebrates, in which the females die during egg development.

The entirety of the stored at a location called a viable eggs are eggs.

Multiple Births

For eggs, it is not impossible - but rarely - that several seedlings are contained in them. In chicken eggs may occasionally happen that in an egg yolk contains several. Such eggs are usually somewhat larger than comparison objects of the same animal. If these eggs fertilized, they would hatch from an egg, ideally two chicks.

Egg as a functional object

The main human use is the egg as food. Also eggs of wild and / or difficult culturable animals are gathered and used here, which for the continued existence of the species can pose a serious threat (for example, sea turtles, caviar).

The world's by far most commonly used bird's egg is the egg, which was used not only as a boiled egg or scrambled eggs and as an ingredient of various dishes, but also in the art and is (for example, in some tempera paints or historic mortar. ) Dyed or decorated hard-boiled eggs or blown decorated egg shells are as Easter egg for Easter.

From the shells of ostrich eggs magnificent, ornate drinking vessels were made ​​earlier in Europe, today lampshades or the jewels are made from the shells.

Eggs as grave goods are occupied since the 4th century.

Criticism of the egg production

In the industrial production of eggs laying hens are used to a race, which are optimized for the laying of eggs - so-called hybrid chickens ( up to 310 eggs per year). When breeding these chickens but also taps are hatched. The rearing of these valves in such a cultured on egg laying breed, not worth but economically. This has the consequence that worldwide approximately 2.5 billion and Germany far about 40 million male chicks after hatching in gassed with CO2 " a kind of chaff cutter with sharp blades crushed " or.

Egg as a designation

(List not complete)

• Egghead (English egghead ) is a colloquial term for scientists ironic. The concept is aimed at the supposedly common among academics ( semi-) bald. Egghead is also the name of a board game.
• Eggs nipples are short nipple tube. They are screwed into the cable outlet of lamp holders and are used for suspension. The relationship with eggs is unclear.