23 Lymnaea is a genus of mollusc with snail-like shells. Members of Lymnaea have shells that coil either left or right.

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23 Lymnaea Is A Genus Of Mollusc With Snail Like Shells Members Of Lymnaea Have Shells That Coil Either Left Or Right 1 (1.81 MiB) Viewed 15 times

23 Lymnaea is a genus of mollusc with snail-like shells. Members of Lymnaea have shells that coil either left or right. In most individuals, development of this trait is purely genetic, with offspring showing a phenotype that is identical to the maternal phenotype. Occasionally, and seemingly at random, an environmental factor influences the outcome and an individual with a genetically right- coiling shell grows a shell that coils left and vice versa. O left-coiled shell right-coiled shell a As a result of physical incompatibility, individuals with shells that coil in the opposite direction are unable to mate. i If the environmental effect were to disappear, the two populations would find mating very difficult. What name is given to this sort of isolation? ii Without the occasional environmental effect on shell growth this incompatibility could lead to speciation of the two groups. Explain how this could occur. b Why is speciation unlikely as long as the environmental effect continues to create individuals that are genetically of one form but phenotypically of the other form?