Practice question

Amphibian eggs contain moderate amount of yolk unevenly distributed, denser at vegetal pole and sparse at animal pole, a condition classified as mesolecithal or moderately telolecithal. This intermediate yolk content distinguishes them from alecithal mammalian and highly telolecithal avian eggs. Because yolk impedes cytokinesis vegetally, cleavage remains holoblastic but unequal, producing small animal micromeres and large vegetal macromeres. Mesolecithal organization permits blastocoel formation and sets up gradients of maternal mRNAs like VegT, influencing germ layer patterning and gastrulation movements for aquatic development.