References

In most species one sex is more reluctant to mate than the other. Standard explanations invoking potential reproductive rates have shortcomings that areSeveral of the mechanisms of gastrulation are conserved among vertebrates [18]. However, the newly described early convergence extension mechanism of the epiblast that takes place at the very beginning of gastrulation appears to be specific to amniotes. This phase might explain the evolutionary change of shape of the blastopore, from a circular structure to the radial slit shape characteristic of the primitive streak