Cleavage is the process by which an embryo develops from a single cell. During cleavage, the embryo divides into smaller and smaller cells, until it reaches a stage called the blastula.

Gastrulation is the process by which the three germ layers (ectoderm, mesoderm, and endoderm) are formed. During gastrulation, the cells of the embryo move and rearrange themselves to form these three layers.

Organogenesis is the process by which organs and tissues are formed from the germ layers. During organogenesis, the cells of the germ layers differentiate into different types of cells, which then form the different organs and tissues of the body.

Metamorphosis is the process by which an animal changes its form and structure after birth. Metamorphosis can be complete, as in the case of a caterpillar changing into a butterfly, or incomplete, as in the case of a tadpole changing into a frog.

Comparative Developmental Biology is the study of the development of different organisms and how they compare to each other. Comparative Developmental Biology is a field of biology that studies the similarities and differences in the development of different organisms.

Neuroectoderm is not a germ layer. The three germ layers are ectoderm, mesoderm, and endoderm.

Sudden is not a type of metamorphosis. The two types of metamorphosis are complete and incomplete.

Chance is not a factor that can affect the development of an organism. The three factors that can affect the development of an organism are genetics, environment, and nutrition.

Cancer is not a type of developmental anomaly. The three types of developmental anomalies are birth defects, genetic disorders, and teratogens.

Paleontology is not a method used to study developmental biology. The three methods used to study developmental biology are embryology, genetics, and molecular biology.

Cell death is not a type of developmental process. The three types of developmental processes are cell division, cell differentiation, and cell migration.

Shh genes are not a type of developmental gene. The three types of developmental genes are Hox genes, Pax genes, and Wnt genes.

Hormones are not a type of developmental signaling molecule. The three types of developmental signaling molecules are growth factors, morphogens, and cytokines.

Cerebral palsy is not a type of developmental disorder. The three types of developmental disorders are autism, Down syndrome, and spina bifida.

Applied research is not a type of developmental research. The three types of developmental research are basic research, clinical research, and translational research.