The homeobox-containing genes that are active in development have been highly _______, meaning they have remained relatively unchanged though the course of evolution. These genes contain information for producing _______.

Three tools that work in development across animal species are cell _______, cell _______, and programmed cell ______.

Human development starts at ________ and continues through _______.

A critical early step in development is the establishment of positional information in the embryo. The local concentration of substances called _________ in the embryo helps impart this information.

Morphogens work by bringing about the production of the proteins called _______, which turn _______ on or off.

Development works from the general to the specific. In Drosophila, the morphogen called bicoid operates early in development by specifying the development of _______ and _______ portions of the embryo.

In animal development, the process of cleavage produces a ball of cells with an interior cavity. In the succeeding evelopmental process, called gastrulation, the cells in the embryo migrate to form three layers of cells, the _______, _______, and _______, which in terms of location are the _______, _______, and ________ layers of cells in the organism.

In vertebrates, a support structure called a notochord serves to _______, or bring about, the development of a structure called the neural tube, which gives rise to both the _______ and _______.

In what way is development a good example of a biological process that is self-regulating?

In what order do the following developmental steps occur?

a. organogenesis

b. fertilization

c. blastula formation

d. morula formation

e. gastrulation