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Moving in water by ciliary motion, eating food by engulfment, reproducing by fission or budding, placozoans are described as "the simplest animals on Earth." [ 6 ] Structural and molecular analyses have supported them as among the most basal animals, [ 7 ] [ 8 ] thus, constituting a primitive metazoan phylum.
A vapor can exist in equilibrium with a liquid (or solid), in which case the gas pressure equals the vapor pressure of the liquid (or solid). A supercritical fluid (SCF) is a gas whose temperature and pressure are above the critical temperature and critical pressure respectively. In this state, the distinction between liquid and gas disappears.
Gas: A compressible fluid. Not only will a gas take the shape of its container but it will also expand to fill the container. Mesomorphic states: States of matter intermediate between solid and liquid. Plastic crystal: A molecular solid with long-range positional order but with constituent molecules retaining rotational freedom.
Jet propulsion is a method of aquatic locomotion where animals fill a muscular cavity and squirt out water to propel them in the opposite direction of the squirting water. Most organisms are equipped with one of two designs for jet propulsion; they can draw water from the rear and expel it from the rear, such as jellyfish, or draw water from ...
Water is the only common substance to exist as a solid, liquid, and gas under conditions normal to life on Earth. [13] The Nobel Prize winner Albert Szent-Györgyi referred to water as the mater und matrix: the mother and womb of life. [14] Composition of seawater. Quantities in relation to 1 kg or 1 litre of sea water.
Aquatic animals generally conduct gas exchange in water by extracting dissolved oxygen via specialised respiratory organs called gills, through the skin or across enteral mucosae, although some are evolved from terrestrial ancestors that re-adapted to aquatic environments (e.g. marine reptiles and marine mammals), in which case they actually ...
Aquatic insects consume the stored air while under water or use it to regulate buoyancy. During a molt, air sacs fill and enlarge as the insect breaks free of the old exoskeleton and expands a new one. Between molts, the air sacs provide room for new growth—shrinking in volume as they are compressed by expansion of internal organs.
Four-stroke buccal pumping is used by some basal ray-finned fish and aquatic amphibians such as Xenopus and Amphiuma. [1] This method has several stages. These will be described for an animal starting with lungs in a deflated state: First, the glottis (opening to the lungs) is closed, and the nostrils are opened.