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| Description: Here we show the first three divisions of cleavage, a process that carves up a zygote’s cytoplasm. In this species, cleavage results in a blastula, a ball of cells with a fluid-filled cavity. Cleavage is over when the blastula forms. The blastula becomes a three-layered gastrula—a process called gastrulation. At the dorsal lip (a fold of ectoderm above the first opening that appears in the blastula), cells migrate inward and start rearranging themselves. Organs begin to form as a primitive gut cavity opens up. A neural tube, then a notochord and other organs, form from the primary tissue layers. The frog’s body form changes as it grows and its tissues specialize. The embryo becomes a tadpole, which metamorphoses into an adult. Tadpole, a swimming larva with segmented muscles and a notochord extending into a tail. Picture Stats: Views: 56 Filesize: 126.26kB Height: 358 Width: 1500 Source: https://biology-forums.com/index.php?action=gallery;sa=view;id=47365 |