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Air sacs are spaces within an organism where there is the constant presence of air. Among modern animals, birds possess the most air sacs (9–11), with their extinct dinosaurian relatives showing a great increase [clarification needed] in the pneumatization (presence of air) in their bones. [1]
The respiratory system (also respiratory apparatus, ventilatory system) is a biological system consisting of specific organs and structures used for gas exchange in animals and plants. The anatomy and physiology that make this happen varies greatly, depending on the size of the organism, the environment in which it lives and its evolutionary ...
The sea slug Pleurobranchaea meckelii respires using a gill which is visible in this view of the right side of the animal. In gastropods in many ancient lineages, the gills are bipectinate, having an overall shape that is similar to a bird's feather, with narrow filaments projecting either side of a central stalk.
Enteral respiration, also referred to as cloacal respiration or intestinal respiration, [1] is a form of respiration in which gas exchange occurs across the epithelia of the enteral system, usually in the caudal cavity .
Gills or gill-like organs, located in different parts of the body, are found in various groups of aquatic animals, including mollusks, crustaceans, insects, fish, and amphibians. Semiterrestrial marine animals such as crabs and mudskippers have gill chambers in which they store water, enabling them to use the dissolved oxygen when they are on land.
In very small animals, plants and bacteria, simple diffusion of gaseous metabolites is sufficient for respiratory function and no special adaptations are found to aid respiration. Passive diffusion or active transport are also sufficient mechanisms for many larger aquatic animals such as many worms, jellyfish, sponges, bryozoans and similar ...
The spiracles are located laterally along the thorax and abdomen of most insects—usually one pair of spiracles per body segment. Air flow is regulated by small muscles that operate one or two flap-like valves within each spiracle—contracting to close the spiracle, or relaxing to open it.
It was assumed to have been a non-discriminatory sediment feeder, processing whatever sediment came its way for food, [77] but fossil findings hint that the last common ancestor of both arthropods and Priapulida shared the same specialized mouth apparatus: a circular mouth with rings of teeth used for capturing animal prey.