An egg is the organic vessel containing the zygote in which an animal embryo develops until it can survive on its own, at which point the animal hatches. An egg results from fertilization of an ovum. Most arthropods, vertebrates, and mollusks lay eggs, although some do not, such as scorpions and most mammals.
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 favorable temperature range (warm) 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 with which to crack, pip, or break the eggshell or covering.
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There are two alleles, the recessive yellow allele and the dominant brown allele. The female is hom0zygous recessive while the male is heterozygous, this means that half of their children will be hom0zygous recessive and be yellow. The other half will be brown and heterozygous, meaning they have a yellow allele and a brown allele. If the female mated with a hom0zygous dominant male, then all of their offspring will end up being heterozygous and brown.
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Trichocyst is a structure in the cortex of certain ciliate and flagellate protozoans consisting of a cavity and long, thin threads that can be ejected in response to certain stimuli. Trichocysts may be widely distributed over an organism or restricted to certain areas.
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