When division of the zygote reaches the eight-cell stage and the planes of cleavage of the upper four cells line up with those of the bottom four cells so that two tiers of cells result,one directly above the other,the type of cleavage is called
A)direct cleavage.
B)spiral cleavage.
C)indirect cleavage.
D)protostome cleavage.
E)radial cleavagE.

Question

Quizplus · Accepted Answer

The description given in the question matches the characteristics of radial cleavage, where the cells divide at right angles to the axis of the embryo, resulting in two tiers of cells stacked on top of one another. Direct cleavage, indirect cleavage, and protostome cleavage do not exhibit this particular pattern of cell division. Spiral cleavage involves oblique or diagonal divisions, resulting in an offset arrangement of cells.

When Division of the Zygote Reaches the Eight-Cell Stage and the Planes