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Embryonic diapause [a] (delayed implantation in mammals) is a reproductive strategy used by a number of animal species across different biological classes.In more than 130 types of mammals where this takes place, the process occurs at the blastocyst stage of embryonic development, [1] and is characterized by a dramatic reduction or complete cessation of mitotic activity, arresting most often ...
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]
A beetle leg. An appendage (or outgrowth) is an external body part or natural prolongation that protrudes from an organism's body such as an arm or a leg. Protrusions from single-celled bacteria and archaea are known as cell-surface appendages or surface appendages.
Different terms are used because of different body plans in animals, whether animals stand on one or two legs, and whether an animal is symmetrical or not, as discussed above. For example, as humans are approximately bilaterally symmetrical organisms, anatomical descriptions usually use the same terms as those for other vertebrates. [ 59 ]
Many vertebrates are limbless, limb-reduced, or apodous, with a body plan consisting of a head and vertebral column, but no adjoining limbs such as legs or fins. Jawless fish are limbless but may have preceded the evolution of vertebrate limbs, whereas numerous reptile and amphibian lineages – and some eels and eel-like fish – independently lost their limbs.
The full development of Oikopleura dioica and the fate of its cell lineages have been well-documented, providing insight into larvacean anatomy. [11] Being a model organism, most of our knowledge on larvaceans comes from this specific taxon. Variations in body shape and anatomy exist between families, [12] although the general body plan stays ...
Modern groups of animals can be grouped by the arrangement of their body structures, so are said to possess different body plans. A body plan, Bauplan (pl. German: Baupläne), or ground plan is a set of morphological features common to many members of a phylum of animals. [1] The vertebrates share one body plan, while invertebrates have many.
Surface projections of the major organs of the trunk, using the vertebral column and rib cage as main reference points of surface anatomy. Surface anatomy (also called superficial anatomy and visual anatomy) is the study of the external features of the body of an animal. [1] In birds, this is termed topography.