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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]
Pregnant male seahorse. Male pregnancy is the incubation of one or more embryos or fetuses by organisms of the male sex in some species. Most species that reproduce by sexual reproduction are heterogamous—females producing larger gametes and males producing smaller gametes ().
The homunculus is commonly used today in scientific disciplines such as psychology as a teaching or memory tool to describe the distorted scale model of a human drawn or sculpted to reflect the relative space human body parts occupy on the somatosensory cortex (the sensory homunculus) and the motor cortex (the motor homunculus).
Human embryology is the study of this development during the first eight weeks after fertilization. The normal period of gestation (pregnancy) is about nine months or 36 weeks. The germinal stage refers to the time from fertilization through the development of the early embryo until implantation is completed in the uterus .
Pregnant scorpion. In viviparous animals, the embryo develops inside the body of the mother, as opposed to outside in an egg . The mother then gives live birth. The less developed form of viviparity is called ovoviviparity, in which the mother carries embryos inside eggs. Most vipers exhibit ovoviviparity. [15]
Drawing of the head of a four-week-old human embryo. From Gray's Anatomy.. Embryo drawing is the illustration of embryos in their developmental sequence.In plants and animals, an embryo develops from a zygote, the single cell that results when an egg and sperm fuse during fertilization.
They approached the horse with caution, and then gently gave her a sniff. The baby then gave the mom-to-be the sweetest little lick, which in cow language is the same as giving her a smooch.
A pregnant lioness. In mammals, pregnancy is the period of reproduction during which a female carries one or more live offspring from implantation in the uterus through gestation. It begins when a fertilized zygote implants in the female's uterus, and ends once it leaves the uterus.