Final answer:
The statement is false; while the ectoderm does form epidermal cells, its default state is not just 'ventral' and it is also responsible for forming neural cells during organogenesis.
Step-by-step explanation:
The statement that the "default" state of the ectoderm in a frog gastrula is a ventral cell type (epidermal ectoderm) is false. The ectoderm is one of the three primary germ layers in an embryo. During gastrulation, ectoderm cells are programmed to develop into different types of tissues, including neural cells and epidermal cells. The default state of ectoderm cells is to become epidermal, but specific growth factors signal some of these cells to form the neural plate, which gives rise to the nervous system. The rest of the ectodermal cells will develop into skin and other epidermal structures. In summary, while it's true the ectoderm will form epidermal cells, it is not defined as ventral in its default state, and it also has the capacity to form neural cells during organogenesis.