<P> The Paramecium spirals through the water as it progresses . When it happens to encounter an obstacle, the "effective stroke" of its cilia is reversed and the organism swims backward for a brief time, before resuming its forward progress . This is called the avoidance reaction . If it runs into the solid object again, it repeats this process, until it can get past the object . </P> <P> It has been calculated that a Paramecium expends more than half of its energy in propelling itself through the water . This ciliary method of locomotion has been found to be less than 1% efficient . This low percentage is nevertheless close to the maximum theoretical efficiency that can be achieved by an organism equipped with cilia as short as those of the members of Paramecium . </P> <P> Paramecia feed on microorganisms like bacteria, algae, and yeasts . To gather food, the Paramecium makes movements with cilia to sweep prey organisms, along with some water, through the oral groove, and inside the mouth opening . The food passes through the cell mouth into the gullet . When enough food has accumulated at the gullet base, it forms a vacuole in the cytoplasm, which then begins circulating through the cell . As it moves along, enzymes from the cytoplasm enter the vacuole to digest the contents; digested nutrients then pass into the cytoplasm, and the vacuole shrinks . When the vacuole, with its fully digested contents, reaches the anal pore, it ruptures, expelling its waste contents to the environment . </P> <P> Some species of Paramecium form mutualistic relationships with other organisms . Paramecium bursaria and Paramecium chlorelligerum harbour endosymbiotic green algae, from which they derive nutrients and a degree of protection from predators such as Didinium nasutum . Numerous bacterial endosymbionts have been identified in species of Paramecium . Some intracellular bacteria, known as Kappa particle s, give Paramecia that have them the ability to kill other strains of Paramecium that lack Kappa . </P>

How does paramecium use cilia to help with nutrition
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