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The biologist Thierry Lodé proposed (2001, 2012) five modes of reproduction based on the relationship between the zygote (fertilised egg) and the parents: [1] [2]. Ovuliparity: fertilisation is external, the oocytes being released into the environment and fertilised outside the body by the male. [1]
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A dual-purpose chicken is a type of chicken that may be used in the production of both eggs and meat. [42] In the past, many chicken breeds were selected for both functions. However, since the advent of laying and meat hybrids, industrial chicken breeding has made a sharp distinction between chickens with either function, [ 43 ] so that certain ...
In the United States alone, more than 8 billion chickens are slaughtered each year for meat, [78] and more than 300 million chickens are reared for egg production. [79] The vast majority of poultry is raised in factory farms. According to the Worldwatch Institute, 74% of the world's poultry meat and 68% of eggs are produced this way. [80]
Chicken and duck eggs on sale in Hong Kong. Poultry is the second most widely eaten type of meat in the world, accounting for about 30% of total meat production worldwide compared to pork at 38%. Sixteen billion birds are raised annually for consumption, more than half of these in industrialised, factory-like production units. [58]
Six commercial chicken eggs — view from the top against a white background. 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.
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.
Voting period is over. Please don't add any new votes. Voting period ends on 10 Jun 2017 at 01:47:55 (UTC). Original – Diagram of a chicken egg in its ninth day of incubation showing all four extraembryonic membranes along with the embryo, the air pocket, and the shell