Ans. The reproductive organs of earthworms are positioned at different ends of their bodies, so that fertilization of the eggs is only possible when the worms are aligned in opposite directions.
Ans. When the evolutionary dynamics of invertebrates are considered, trochophore larva attracts special attention as it shows prominent similarities with some other groups of invertebrates. The affinities with other groups suggest to conclude that the animals having bilateral symmetry emerge from those of having radial symmetry. It is assumed that the trochophore represents a transitional [...]
Ans.: In some groups of annelids nephridia and coelomducts are separate. But in some Polychaeta, coelomducts do not remain independent but become fused with the nephridia forming compound segmental organs or nephromixia. They are consisting of ectoderm and mesoderm and used both as genital as well as excretory duct.
Ans.: Metamerism gives many advantages for the animals. It helps in locomotion by many ways. Fluid filled coelomic compartments provide hydrostatic skeleton for burrowing in annelids, metamerism offers divisions of labour.
Ans.: Metamerism is the phenomenon in which the body of an animal is divided into antero-posterior row of similar part or sections. These sections are called as segments or metamers. It involves a longitudinal division of body of a bilaterally symmetrical organism in to a linear series of similar segments.
