Source: NOVA: "The Shape of Things"
NARRATOR: While this mallard's young are in their eggs, patterns are developing that not only sustain life, but also anticipate the emerging adult form. Within days, cells specialize into a nervous system and a spinal column. The living thing is beginning to take shape.
Blood cells form, and with them, the cells for veins and arteries. Together they make a river of their own, like a tree, a limb, a leaf, a branching pattern for moving the raw materials for growth. It is the simplest way for all parts of a growing embryo to be nourished.
This tiny heart drives a system of distribution, and a pattern emerges. At the center, the vessels are biggest, as they are in a leaf, the flow greatest. At the extremities, the capillaries, reaching every single growing cell. The heart pumps the blood that connects the source of food in the yolk with the growing embryo.
The system carries blood to the interface with the porous shell, where carbon dioxide is exchanged for oxygen. The yolk has all the raw material from which the embryo will construct itself. It has 28 days to grow all the systems it will need to break free and survive in the world outside.
The shell breaks easily when pushed from the inside. Weak as it is, the duckling breaks out (duckling chirping). It's an extraordinary process. The bird grew from a single cell into a complex body that includes a beak, webbed feet, bones, and feathers. Each of these will soon toughen into the specialized features that suit ducks so well to their environment.
Academic standards correlations on Teachers' Domain use the Achievement Standards Network (ASN) database of state and national standards, provided to NSDL projects courtesy of JES & Co.
We assign reference terms to each statement within a standards document and to each media resource, and correlations are based upon matches of these terms for a given grade band. If a particular standards document of interest to you is not displayed yet, it most likely has not yet been processed by ASN or by Teachers' Domain. We will be adding social studies and arts correlations over the coming year, and also will be increasing the specificity of alignment.