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In animals, the process involves a sperm fusing with an ovum, which eventually leads to the development of an embryo. Depending on the animal species, the process can occur within the body of the female in internal fertilization, or outside in the case of external fertilization. The fertilized egg cell is known as the zygote. [2] [5]
Also gastrocoel. The central internal cavity of the gastrula in most animal embryos, fated to develop into the lumen of the digestive tube ; the primitive gut. The archenteron initially has only one open end, known as the blastopore. B birth blastocoel Also blastocoele, blastocele, cleavage cavity, and segmentation cavity. The fluid-filled or yolk -filled cavity that forms in the developing ...
The following outline is provided as an overview of and topical guide to zoology: . Zoology – study of animals.Zoology, or "animal biology", is the branch of biology that relates to the animal kingdom, including the identification, structure, embryology, evolution, classification, habits, and distribution of all animals, both living and extinct, and how they interact with their ecosystems.
Embryology is the subdivision of developmental biology that studies embryos and their development. The main article for this category is Embryology . Contents
Due to the fact that placental mammals and marsupials nourish their developing embryos via the placenta, the ovum in these species does not contain significant amounts of yolk, and the yolk sac in the embryo is relatively small in size, in comparison with both the size of the embryo itself and the size of yolk sac in embryos of comparable developmental age from lower chordates.
But most interest by developmental biologists has been shown in the regeneration of parts in free living animals. In particular four models have been the subject of much investigation. Two of these have the ability to regenerate whole bodies: Hydra , which can regenerate any part of the polyp from a small fragment, [ 9 ] and planarian worms ...
In birds, the organizer is known as Hensen's node, named after its discoverer Victor Hensen.; In other amniotes, it is known as the primitive node.; In amphibians, it is known as the Spemann-Mangold organizer, named after Hans Spemann and Hilde Mangold, who first identified the organizer in 1924.
In embryology, Carnegie stages are a standardized system of 23 stages used to provide a unified developmental chronology of the vertebrate embryo.. The stages are delineated through the development of structures, not by size or the number of days of development, and so the chronology can vary between species, and to a certain extent between embryos.