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Egg
An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the animal hatches. Most arthropods such as insects, vertebrates (excluding live-bearing mammals), and mollusks lay eggs, although some, such as scorpions, do not. Reptile eggs, bird eggs, and monotreme eggs are laid out of water and are surrounded by a protective shell, either flexible or inflexible. Eggs laid on land or in nests are usually kept within a warm and favorable temperature range while the embryo grows. When the embryo is adequately developed it hatches, i.e., breaks out of the egg's shell. Some embryos have a temporary egg tooth they use to crack, pip, or break the eggshell or covering. The largest recorded egg is from a whale shark and was in size. Whale shark eggs typically hatch within the mother. At and up to , the ostri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eggshell
An eggshell is the outer covering of a hard-shelled egg and of some forms of eggs with soft outer coats. Diversity Worm eggs Nematode eggs present a two layered structure: an external vitellin layer made of chitin that confers mechanical resistance and an internal lipid-rich layer that makes the egg chamber impermeable. Insect eggs Insects and other arthropods lay a large variety of styles and shapes of eggs. Some of them have gelatinous or skin-like coverings, others have hard eggshells. Softer shells are mostly protein. It may be fibrous or quite liquid. Some arthropod eggs do not actually have shells, rather, their outer covering is actually the outermost embryonic membrane, the choroid, which serves to protect inner layers. The choroid itself can be a complex structure, and it may have different layers within it. It may have an outermost layer called an ''exochorion''. Eggs which must survive in dry conditions usually have hard eggshells, made mostly of dehydrated ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bird Egg
Bird eggs are laid by the females and range in quantity from one (as in condors) to up to seventeen (the grey partridge). Clutch size may vary latitudinally within a species. Some birds lay eggs even when the eggs have not been fertilized; it is not uncommon for pet owners to find their lone bird nesting on a clutch of infertile eggs, which are sometimes called wind-eggs. Anatomy All bird eggs contain the following components: * The embryo is the immature developing chick * The amnion is a membrane that initially covers the embryo and eventually fills with amniotic fluid, provides the embryo with protection against shock from movement * The allantois helps the embryo obtain oxygen and handles metabolic waste * The chorion, together with the amnion, forms the amniotic sac and encloses the amnion, vitellus, and the embryo * The vitellus, or yolk, is the nutrient-bearing portion of the egg, containing most of its fat, minerals, and many of its proteins and blood vessels * The a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Elephant Bird
Elephant birds are members of the extinct ratite family Aepyornithidae, made up of flightless birds that once lived on the island of Madagascar. They are thought to have become extinct around 1000-1200 CE, probably as a result of human activity. Elephant birds comprised the genera ''Mullerornis'', '' Vorombe'' and '' Aepyornis''. While they were in close geographical proximity to the ostrich, their closest living relatives are kiwi (found only in New Zealand), suggesting that ratites did not diversify by vicariance during the breakup of Gondwana but instead evolved from ancestors that dispersed more recently by flying. In September 2018, scientists determined that ''Vorombe titan'' reached weights of and stood tall, making it the world's largest and heaviest bird, slightly larger than the much older '' Dromornis stirtoni''. Other members of the family were also very large, exhibiting the phenomenon of island gigantism. Description Elephant birds have been extinct si ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chicken Egg Diagram
The chicken (''Gallus gallus domesticus'') is a domesticated junglefowl species, with attributes of wild species such as the grey and the Ceylon junglefowl that are originally from Southeastern Asia. Rooster or cock is a term for an adult male bird, and a younger male may be called a cockerel. A male that has been castrated is a capon. An adult female bird is called a hen and a sexually immature female is called a pullet. Humans now keep chickens primarily as a source of food (consuming both their meat and eggs) and as pets. Traditionally they were also bred for cockfighting, which is still practiced in some places. Chickens are one of the most common and widespread domestic animals, with a total population of 23.7 billion , up from more than 19 billion in 2011. There are more chickens in the world than any other bird. There are numerous cultural references to chickens – in myth, folklore and religion, and in language and literature. Genetic studies have pointed to mu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Egg Cell
The egg cell, or ovum (plural ova), is the female reproductive cell, or gamete, in most anisogamous organisms (organisms that reproduce sexually with a larger, female gamete and a smaller, male one). The term is used when the female gamete is not capable of movement (non- motile). If the male gamete (sperm) is capable of movement, the type of sexual reproduction is also classified as oogamous. A nonmotile female gamete formed in the oogonium of some algae, fungi, oomycetes, or bryophytes is an oosphere. When fertilized the oosphere becomes the oospore. When egg and sperm fuse during fertilisation, a diploid cell (the zygote) is formed, which rapidly grows into a new organism. History While the non-mammalian animal egg was obvious, the doctrine ''ex ovo omne vivum'' ("every living nimal comes froman egg"), associated with William Harvey (1578–1657), was a rejection of spontaneous generation and preformationism as well as a bold assumption that mammals also reproduced ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Egg Incubation
Egg incubation is the process by which an egg, of oviparous (egg-laying) animals, develops an embryo within the egg, after the egg's formation and ovipositional release. Egg incubation is done under favorable environmental conditions, possibly by brooding and hatching the egg. Multiple and various factors are vital to the incubation of various species of animal. In many species of reptile for example, no fixed temperature is necessary, but the actual temperature determines the sex ratio of the offspring. In birds in contrast, the sex of offspring is genetically determined, but in many species a constant and particular temperature is necessary for successful incubation. Especially in poultry, the act of sitting on eggs to incubate them is called brooding. The action or behavioral tendency to sit on a clutch of eggs is also called broodiness, and most egg-laying breeds of poultry have had this behavior selectively bred out of them to increase production. Avian incubation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Egg Tooth
An egg tooth is a temporary, sharp projection present on the bill or snout of an oviparous animal at hatching. It allows the hatchling to penetrate the eggshell from inside and break free. Birds, reptiles, and monotremes possess egg teeth as hatchlings. Similar structures exist in Eleutherodactyl frogs, and spiders. Birds When it is close to hatching, a chick uses its egg tooth to pierce the air sac between the membrane and the eggshell. This sac provides a few hours' worth of air, during which time the chick hatches. When a chick is ready to hatch from its egg, it begins the process of "pipping"; forcing the egg tooth through the shell repeatedly as the embryo rotates, eventually cutting away a section at the blunt end of the egg, leaving a hole through which the bird may emerge. Some species, including woodpeckers, have two egg teeth; one on both the upper and lower bill. After time the egg tooth falls off or is absorbed into the growing chick's bill. Some precocial speci ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Non-avian Dinosaur
Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is the subject of active research. They became the dominant terrestrial vertebrates after the Triassic–Jurassic extinction event 201.3 mya; their dominance continued throughout the Jurassic and Cretaceous periods. The fossil record shows that birds are feathered dinosaurs, having evolved from earlier theropods during the Late Jurassic epoch, and are the only dinosaur lineage known to have survived the Cretaceous–Paleogene extinction event approximately 66 mya. Dinosaurs can therefore be divided into avian dinosaurs—birds—and the extinct non-avian dinosaurs, which are all dinosaurs other than birds. Dinosaurs are varied from taxonomic, morphological and ecological standpoints. Birds, at over 10,700 living species, are am ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zygote
A zygote (, ) is a eukaryotic cell formed by a fertilization event between two gametes. The zygote's genome is a combination of the DNA in each gamete, and contains all of the genetic information of a new individual organism. In multicellular organisms, the zygote is the earliest developmental stage. In humans and most other anisogamous organisms, a zygote is formed when an egg cell and sperm cell come together to create a new unique organism. In single-celled organisms, the zygote can divide asexually by mitosis to produce identical offspring. German zoologists Oscar and Richard Hertwig made some of the first discoveries on animal zygote formation in the late 19th century. Humans In human fertilization, a released ovum (a haploid secondary oocyte with replicate chromosome copies) and a haploid sperm cell (male gamete) combine to form a single diploid cell called the zygote. Once the single sperm fuses with the oocyte, the latter completes the division of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Monotreme
Monotremes () are prototherian mammals of the order Monotremata. They are one of the three groups of living mammals, along with placentals ( Eutheria), and marsupials (Metatheria). Monotremes are typified by structural differences in their brains, jaws, digestive tract, reproductive tract, and other body parts, compared to the more common mammalian types. In addition, they lay eggs rather than bearing live young, but, like all mammals, the female monotremes nurse their young with milk. Monotremes have been considered members of Australosphenida, a clade that contains extinct mammals from the Jurassic and Cretaceous of Madagascar, South America, and Australia, though this is disputed. The only surviving examples of monotremes are all indigenous to Australia and New Guinea, although there is evidence that they were once more widespread, as '' Monotrematum'' is known from the Paleocene of South America. The extant monotreme species are the platypus and four species of echidna ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reptile
Reptiles, as most commonly defined are the animals in the class Reptilia ( ), a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates (lizards and snakes) and rhynchocephalians ( tuatara). As of March 2022, the Reptile Database includes about 11,700 species. In the traditional Linnaean classification system, birds are considered a separate class to reptiles. However, crocodilians are more closely related to birds than they are to other living reptiles, and so modern cladistic classification systems include birds within Reptilia, redefining the term as a clade. Other cladistic definitions abandon the term reptile altogether in favor of the clade Sauropsida, which refers to all amniotes more closely related to modern reptiles than to mammals. The study of the traditional reptile orders, historically combined with that of modern amphibians, is called herpetology. The earliest known proto-reptiles originated ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ostrich
Ostriches are large flightless birds of the genus ''Struthio'' in the order Struthioniformes, part of the infra-class Palaeognathae, a diverse group of flightless birds also known as ratites that includes the emus, rheas, and kiwis. There are two living species of ostrich: the common ostrich, native to large areas of sub-Saharan Africa and the Somali ostrich, native to the Horn of Africa. The common ostrich was also historically native to the Arabian Peninsula, and ostriches were present across Asia as far east as Mongolia during the Late Pleistocene and possibly into the Holocene. They lay the largest eggs of any living land animal. With the ability to run at 70 km/h (43.5 mph), they are the fastest birds on land. They are farmed worldwide, particularly for their feathers as they are used as decoration and feather dusters. Their skin is also used for leather products. They are the heaviest living birds. Taxonomic history The genus ''Struthio'' was first des ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
