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Sessile animals can move via external forces (such as water currents), but are usually permanently attached to something. Organisms such as corals lay down their own substrate from which they grow. Other animals organisms grow from a solid object, such as a rock, a dead tree trunk, or a human-made object such as a buoy or ship's hull.
As with all Cnidarians, these organisms have a complex life cycle including a motile planktonic phase and a later characteristic sessile phase. Hexacorallia also include the significant extinct order of rugose corals .
All cells can be considered motile for having the ability to divide into two new daughter cells. [1] Motility is the ability of an organism to move independently using metabolic energy. This biological concept encompasses movement at various levels, from whole organisms to cells and subcellular components.
Some organisms are motile throughout their lives, but others are adapted to move or be moved at precise, limited phases of their life cycles. This is commonly called the dispersive phase of the life cycle. The strategies of organisms' entire life cycles often are predicated on the nature and circumstances of their dispersive phases.
Species of Ulva, the sea lettuce, have gametes which all have two flagella and so are motile. However they are of two sizes: larger 'female' gametes and smaller 'male' gametes. [22] One large and sessile, one small and motile (oogamy). The larger sessile megagametes are eggs (ova), and smaller motile microgametes are sperm (spermatozoa ...
Sessility, or sessile, may refer to: Sessility (motility), organisms which are not able to move about; Sessility (botany), flowers or leaves that grow directly from the stem or peduncle of a plant; Sessility (medicine), tumors and polyps that lack a stalk
The larvae of sessile forms which survive eventually settle and complete maturation on the substratum- then they may bud asexually to form a colony of zooids. The picture is more complicated for the philopatrically dispersed ascidians: sperm from a nearby colony (or from a zooid of the same colony) enter the atrial siphon and fertilization ...
The majority of crinoids are motile, but sea lilies are sessile and attached to hard substrates by stalks. Movement in most sea lilies is limited to bending (their stems can bend) and rolling and unrolling their arms; a few species can relocate themselves on the seabed by crawling.