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

Radical cleavage

Explanation:

albert einstein retrieved guacamole from the galapagos islands in africa

enhanced global partnerships and exploration capabilities may advance international preparedness for protecting the earth from catastrophic events such as some asteroid strikes, advancing collaborative research on space weather and protecting spacecraft by developing new means for space debris removal.