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Diagram of stages of embryo development to a larval and adult stage. In developmental biology, animal embryonic development, also known as animal embryogenesis, is the developmental stage of an animal embryo. Embryonic development starts with the fertilization of an egg cell (ovum) by a sperm cell (spermatozoon). [1]
Human embryonic development covers the first eight weeks of development, which have 23 stages, called Carnegie stages. At the beginning of the ninth week, the embryo is termed a fetus (spelled "foetus" in British English). In comparison to the embryo, the fetus has more recognizable external features and a more complete set of developing organs.
The development of the reproductive system is the part of embryonic growth that results in the sex organs and contributes to sexual differentiation. Due to its large overlap with development of the urinary system , the two systems are typically described together as the genitourinary system .
Prenatal development (from Latin natalis 'relating to birth') involves the development of the embryo and of the fetus during a viviparous animal's gestation. Prenatal development starts with fertilization , in the germinal stage of embryonic development, and continues in fetal development until birth .
Plant development is the process by which structures originate and mature as a plant grows. It is studied in plant anatomy and plant physiology as well as plant morphology. Plants constantly produce new tissues and structures throughout their life from meristems [ 36 ] located at the tips of organs, or between mature tissues.
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In embryology, cleavage is the division of cells in the early development of the embryo, following fertilization. [1] The zygotes of many species undergo rapid cell cycles with no significant overall growth, producing a cluster of cells the same size as the original zygote.
A puppy is a juvenile dog, generally one less than 12-18 months old. Puppies are markedly underdeveloped and dependent on their mothers at birth (displaying altriciality), but healthy puppies grow quickly and begin walking thereafter. Puppies generally weigh 8–16 oz (0.23–0.45 kg) shortly after birth, depending on the breed. [1]