NationMaster - Encyclopedia: Egg (biology)

In most birds and reptiles, an egg (Latin ovum) is the zygote, resulting from fertilization of the ovum. To enable incubation the egg is usually kept within a favourable temperature range as it nourishes and protects the growing embryo. When the embryo is adequately developed it breaks out of the egg in the process of hatching. Some embryos have a temporary egg tooth with which to crack or pip the eggshell or covering. For other uses, see Bird (disambiguation). ... Subclasses Anapsida Diapsida Synonyms Reptilia Laurenti, 1768 Reptiles are tetrapods and amniotes, animals whose embryos are surrounded by an amniotic membrane, and members of the class Sauropsida. ... Latin was the language originally spoken in the region around Rome called Latium. ... It has been suggested that Biparental zygote be merged into this article or section. ... Categories: Biology stubs ... A human ovum Sperm cells attempting to fertilize an ovum An ovum (plural ova) is a haploid female reproductive cell or gamete. ... For other uses, see Embryo (disambiguation). ... An egg tooth is not a true tooth, but a small horny protruberance on the beak or nose of vertebrates that are hatched from eggs, ie: birds and reptiles. ...

Oviparous animals are animals that lay eggs, with little or no other development within the mother. The study or collecting of eggs, particularly bird eggs, is called oology. Oology is the branch of zoology that deals with the study of eggs, especially birds eggs. ...

Reptile eggs, bird eggs, and monotreme eggs, which are laid out of water, are surrounded by a protective shell, either flexible or inflexible. The term eggshell is a term for the outer covering of a hard-shelled egg, and some forms of eggs with soft outer coats. ...

The 1.5 kg ostrich egg contains the largest existing single cell currently known, though the extinct Aepyornis and some dinosaurs had larger eggs. The Bee Hummingbird produces the smallest known bird egg, which weighs half a gram. The eggs laid by some reptiles and most fish are even smaller, and those of insects and other invertebrates are much smaller still. Binomial name Carolus Linnaeus, 1758 The present-day distribution of Ostriches. ... Species Aepyornis hildebrandti Aepyornis medius Aepyornis maximus Aepyornis is an extinct genus of flightless bird. ... Orders & Suborders Saurischia Sauropodomorpha Theropoda Ornithischia Thyreophora Ornithopoda Marginocephalia Dinosaurs were vertebrate animals that dominated the terrestrial ecosystem for over 160 million years, first appearing approximately 230 million years ago. ... Binomial name Mellisuga helenae (Lembeye, 1850) The Bee Hummingbird (Mellisuga helenae) is a hummingbird, and the smallest of all birds (with the male being smaller than the female of the species). ... Invertebrate is a term that describes any animal without a spinal column. ...

Bird eggs

Bird eggs are laid by females and incubated for a time that varies according to the species; a single young hatches from each egg. Average clutch sizes range from one (as in condors) to about 17 (the Grey Partridge). Some birds lay eggs even when not fertilized; it is not uncommon for pet owners to find their lone bird nesting on a clutch of infertile eggs. The word incubate in the context of birds refers to the development of the chick (embryo) within the egg and the constant temperature required for the development of it over a specific period. ... A clutch of blackbird (Turdus merula) eggs. ... Genera Vultur Gymnogyps For other uses, see Condor (disambiguation). ... Binomial name Perdix perdix (Linnaeus, 1758) The Grey Partridge (Perdix perdix) is a gamebird in pheasant family Phasianidae of the order Galliformes, gallinaceous birds. ...

Colors

The default color of vertebrate eggs is the white of the calcium carbonate from which the shells are made, but some birds, mainly passerines, produce colored eggs. The pigments biliverdin and its zinc chelate give a green or blue ground color, and protoporphyrin produces reds and browns as a ground color or as spotting. http://www. ... http://www. ... Calcium carbonate is a chemical compound, with the chemical formula CaCO3. ... Families Many, see text A passerine is a bird of the giant order Passeriformes. ... Biliverdin is a green pigment formed as a byproduct of hemoglobin breakdown. ... Chelation (from Greek, claw like) describes the reversible binding of an organic ligand, the chelator or chelating agent, to a metal ion, forming a metal complex, the chelate. ... Protoporphyrins are tetrapyrroles containing the following side chains: methyl (4) propionic acid (2) vinyl (2) In the metabolism of porphyrin, protoporphyrin IX is created by the enzyme protoporphyrinogen oxidase, and the enzyme ferrochelatase converts it into heme. ...

Non-passerines typically have white eggs, except in some ground-nesting groups such as the Charadriiformes, sandgrouse and nightjars, where camouflage is necessary, and some parasitic cuckoos which have to match the passerine host's egg. Most passerines, in contrast, lay colored eggs, even if there is no need of cryptic colors. Families Thinocoridae Pedionomidae Scolopacidae Rostratulidae Jacanidae Chionididae Burhinidae Haematopodidae Recurvirostridae Ibidorhynchidae Charadriidae Pluvianellidae Dromadidae Glareolidae Stercorariidae Rhynchopidae Laridae Sternidae Alcidae Charadriiformes is a diverse order of small to medium-large birds. ... Genera Pterocles Syrrhaptes The sandgrouse are a group of 16 near passerine bird species in the order Pteroclidiformes. ... Genera Nyctiprogne Podager Lurocalis Chordeiles Nyctidromus Phalaenoptilus Siphonorhis Nyctiphrynus Caprimulgus Macrodipteryx Hydropsalis Uropsalis Macropsalis Eleothreptus Eurostopodus Nightjars are medium-sized nocturnal birds with long wings, short legs and very short bills that usually nest on the ground. ... A Common Cuckoo being raised by a Reed Warbler. ... Genera See text. ...

However, a recent study suggests that the protoporphyrin markings on passerine eggs actually act to reduce brittleness by acting as a solid state lubricant. If there is insufficient calcium available in the local soil, the egg shell may be thin, especially in a circle around the broad end. Protoporphyrin speckling compensates for this, and increases inversely to the amount of calcium in the soil.

For the same reason, later eggs in a clutch are more spotted than early ones as the female's store of calcium is depleted.

The color of individual eggs is also genetically influenced, and appears to be inherited through the mother only, suggesting that the gene responsible for pigmentation is on the sex determining W chromosome (female birds are WZ, males ZZ). For a non-technical introduction to the topic, see Introduction to Genetics. ... The ZW sex-determination system is a system that birds, some fishes, and some insects (including butterflies and moths) use to determine the sex of their offspring. ...

It used to be thought that color was applied to the shell immediately before laying, but this research shows that coloration is an integral part of the development of the shell, with the same protein responsible for depositing calcium carbonate, or protoporphyrins when there is a lack of that mineral.

In species such as the Common Guillemot, which nest in large groups, each female's eggs have very different markings, making it easier for females to identify their own eggs on the crowded cliff ledges on which they breed. Binomial name Uria aalge (Pontoppidan, 1763) The Common Guillemot, known as the Common Murre in North America, Uria aalge, is a large alcid. ...

Shell

Tiny pores in bird eggshells allow the embryo to breathe. The domestic hen's egg has around 7500 pores. For other uses, see Cormorant (disambiguation). ... Genera Tinamus Nothocercus Crypturellus Rhynchotus Nothoprocta Nothura Taoniscus Eudromia Tinamotis The tinamous are one of the most ancient groups of bird, members of a South American bird family of about 47 species in 9 genera. ... Subfamilies Dendrocygninae Oxyurinae Anatinae Aythyinae Merginae Duck is the common name for a number of species in the Anatidae family of birds. ... Species Casuarius casuarius Casuarius unappendiculatus Casuarius bennetti Cassowaries (genus Casuarius) are very large flightless birds native to the tropical forests of New Guinea and northeastern Australia. ... A pore, in general, is some form of opening, usually very small. ... This article or section does not adequately cite its references or sources. ...

Shape

Most bird eggs have an oval shape, with one end rounded and the other more pointy. This shape results from the egg being forced through the oviduct. Muscles contract the oviduct behind the egg, pushing it forward. The egg's wall is still shapeable, and the pointy end develops at the back side. Cliff-nesting birds often have highly conical eggs. They are less likely to roll off, tending instead to roll around in a tight circle, and thus are believed to have been selected for by evolution. In contrast many hole-nesting birds have nearly spherical eggs. In geometry, an oval or ovoid (from Latin ovum, egg) is any curve resembling an egg or an ellipse. ... In oviparous animals (those that lay eggs), the passage from the ovaries to the outside of the body is known as the oviduct. ...

Predation

Many animals feed on eggs. For example, principal predators of the Black Oystercatcher's eggs include raccoons, skunks, mink, river and sea otters, gulls, crows and foxes. The stoat (Mustela erminea) and long-tailed weasel (M. frenata) steal ducks' eggs. Snakes of the genera Dasypeltis and Elachistodon specialize in eating eggs. Binomial name Haematopus bachmani (Audubon, 1838) The American Black Oystercatcher, Haematopus bachmani, is a conspicuous black bird found on the shoreline of western North America. ... Type species Procyon lotor Linnaeus, 1758 Species Procyon cancrivorus Procyon insularis Procyon lotor This article is about genus Procyon. ... Genera Conepatus Mydaus Mephitis Spilogale Skunks are mammals, usually with black-and-white fur, that are best known for their ability to excrete a strong foul smelling odor. ... Species Mustela vison Mustela vison evergladensis Mustela lutreola Mustela macrodon A mink is any of several furry, dark-coloured, semi-aquatic, carnivorous mammals of the family Mustelidae, which also includes the weasels and the otters. ... Genera Amblonyx Aonyx Enhydra Lontra Lutra Lutrogale Pteronura The otter (lutrinae) is a carnivorous aquatic or marine mammal part of the family Mustelidae, which also includes weasels, polecats, badgers, as well as others. ... â€œSeagullâ€ redirects here. ... Species See text. ... This article needs additional references or sources for verification. ... Binomial name Linnaeus, 1758 Range map The stoat (Mustela erminea) is a small mammal of the family Mustelidae. ... Binomial name Mustela frenata Lichtenstein, 1831 The Long-tailed Weasel (Mustela frenata) is the most widely distributed mustelid in the New World. ... Species 5 recognized species, see article. ... Binomial name Elachistodon westermanni (Reinhardt, 1863) Indian Egg-eating Snake (Elachistodon westermanni) is a rare species of egg-eating snake found in Bangladesh, India, and Nepal. ...

Brood parasitism occurs in birds when one species lays its eggs in the nest of another. In some cases, the host's eggs are removed or eaten by the female, or expelled by her chick. Brood parasites include the cowbirds and many Old World cuckoos. Brood parasites are a sub-category of kleptoparasite occurring among birds or insects, that lay their eggs in the nests of other species to be raised by the host. ... Species Molothrus rufoaxillaris Molothrus oryzivorus Molothrus aeneus Molothrus bonariensis Molothrus ater Cowbirds are birds belonging to the genus Molothrus in the family Icteridae. ... Genera See text. ...

Various bird eggs

Fish eggs

The most common reproductive strategy for fish is known as oviparity, in which the female lays undeveloped eggs that are externally fertilized by a male. Typically large numbers of eggs are laid at one time (an adult female cod can produce 4–6 million eggs in one spawning) and the eggs are then left to develop without parental care. When the larvae hatch from the egg, they often carry the remains of the yolk in a yolk sac which continues to nourish the larvae for a few days as they learn how to swim. Once the yolk is consumed, there is a critical point after which they must learn how to hunt and feed or they will die. Image File history File links Download high resolution version (1249x1821, 178 KB) Salmon larva image Uwe Kils File links The following pages link to this file: Salmon User talk:Kils Egg yolk User:Kils/gallery ... Image File history File links Download high resolution version (1249x1821, 178 KB) Salmon larva image Uwe Kils File links The following pages link to this file: Salmon User talk:Kils Egg yolk User:Kils/gallery ... Illustration of a male Coho Salmon The Chinook or King Salmon is the largest salmon in North America and can grow to 1. ... Image File history File links Download high resolution version (1860x1308, 173 KB)salmon eggs image uwe kils gfdl self File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links Download high resolution version (1860x1308, 173 KB)salmon eggs image uwe kils gfdl self File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... The egg yolk is the yellow inside an egg. ... For other uses, see Fish (disambiguation). ... Oviparous animals are animals that lay eggs, with little or no other embryonic development within the mother. ... the world is coming to the end!!!!! cod is going to eat up alive and do us hard up the emmm. ...

A few fish, notably the rays and most sharks use ovoviviparity in which the eggs are fertilized and develop internally. However the larvae still grow inside the egg consuming the egg's yolk and without any direct nourishment from the mother. The mother then gives birth to relatively mature young. In certain instances, the most physically-developed offspring will devour its smaller siblings for further nutrition while still within the mother's body. This is known as intrauterine cannibalism. Orders Rajiformes- common rays and skates Myliobatiformes - eagle rays, manta rays Pristiformes - sawfishes Torpediniformes - electric rays Rays are a 400 species group (superorder Rajomorphii or Batoidea) of cartilaginous fishes divided into seven families. ... Orders Carcharhiniformes Heterodontiformes Hexanchiformes Lamniformes Orectolobiformes Pristiophoriformes Squaliformes Squatiniformes â€ Symmoriida Sharks (superorder Selachimorpha) are fish with a full cartilaginous skeleton [1] and a streamlined body. ... Ovoviviparous animals develop within eggs that remain within the mothers body up until they hatch or are about to hatch. ... Intrauterine cannibalism is a behaviour in some carnivorous species, in which multiple embryos are created at impregnation, but only one or two are born. ...

More rarely, some fish such as the hammerhead shark and reef shark are viviparous, with the egg being fertilized and developed internally, but with the mother also providing direct nourishment.
Species See text. ... Several species of reef-associated sharks are known as reef sharks: Grey reef shark, Carcharhinus amblyrhynchos. ... A viviparous animal is an animal employing vivipary, a method of reproduction in which the embryo develops inside the body of the mother from which it gains nourishment, and not from an egg. ...

Other eggs

Reptile eggs are often rubbery and are always initially white. Often the sex of the developing embryo is determined by the temperature of the surroundings, with cooler temperatures favouring males. Not all reptiles lay eggs; some are viviparous. Image File history File links Download high-resolution version (1531x1021, 252 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Snapping turtle Egg (biology) User:Moondigger ... Image File history File links Download high-resolution version (1531x1021, 252 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Snapping turtle Egg (biology) User:Moondigger ... Binomial name Chelydra serpentina Linnaeus, 1758 Common Snapping Turtle head Snapping Turtles (Chelydra serpentina) are more formally referred to as Common Snapping Turtles when distinguishing them from their larger cousins (Macrochelys), and are popularly nicknamed snappers. ... Image File history File linksMetadata Download high-resolution version (1536x1152, 387 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Egg (biology) Metadata This file contains additional information, probably added from the digital camera or scanner used to... Image File history File linksMetadata Download high-resolution version (1536x1152, 387 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Egg (biology) Metadata This file contains additional information, probably added from the digital camera or scanner used to... A viviparous animal is an animal employing vivipary, a method of reproduction in which the embryo develops inside the body of the mother from which it gains nourishment, and not from an egg. ...

Like fish eggs, amphibian eggs are jellylike and are fertilized externally. They also do not have a shell and therefore need to be laid in water or protective foam as with the Coast foam-nest treefrog, Chiromantis xerampelina.

Other than extinct species, mammal eggs are laid only by Australian monotremes: the platypus and two genera of echidna (spiny anteaters). Families Kollikodontidae (extinct) Ornithorhynchidae - Platypus Tachyglossidae - Echidnas Steropodontidae (extinct) Monotremes are mammals that are best known for laying eggs, instead of giving birth to live young like marsupials and placental mammals (Eutheria). ... Binomial name (Shaw, 1799) Platypus range (indicated by darker shading)[3] The Platypus (Ornithorhynchus anatinus) is a semi-aquatic mammal endemic to eastern Australia, including Tasmania. ... Species Genus Tachyglossus T. aculeatus Genus Zaglossus Z. attenboroughi Z. bruijnii Z. bartoni â€ Z. hacketti â€ Z. robustus Genus â€ Megalibgwilia â€ M. ramsayi â€ M. robusta For other senses of this word, see echidna (disambiguation). ...

References

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