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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.
Ileum, caecum and colon of rabbit, showing Appendix vermiformis on fully functional caecum The human vermiform appendix on the vestigial caecum. The appendix was once believed to be a vestige of a redundant organ that in ancestral species had digestive functions, much as it still does in extant species in which intestinal flora hydrolyze cellulose and similar indigestible plant materials. [10]
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.
Cervical rib; Fabella; Foramen tympanicum; Supracondylar process of the humerus; Sternal foramen; Stafne bone cavity; Episternal ossicles; Fossa navicularis magna
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.
For example, structures may be described relative to the anterior superior iliac spine, the medial malleolus or the medial epicondyle. Anatomical lines are used to describe anatomical location. For example, the mid-clavicular line is used as part of the cardiac exam in medicine to feel the apex beat of the heart.
There are structural differences between the limb anatomy of plantigrades, unguligrades, and digitigrades. Digitigrade and unguligrade animals have relatively long carpals and tarsals, and the bones which correspond to the human ankle are thus set much higher in the limb than in a human. In a digitigrade animal, this effectively lengthens the ...
A study in 1992 estimated that there were 500,000 species of animals and plants in Costa Rica alone, of which 365,000 were arthropods. [ 38 ] They are important members of marine, freshwater, land and air ecosystems and one of only two major animal groups that have adapted to life in dry environments; the other is amniotes , whose living ...