The entire thing describes the process by which life develops and changes over time.
Seriously, it's right in the definition of "develop":
[dih-vel-uh p]
verb (used with object)
1. to bring out the capabilities or possibilities of; bring to a more advanced or effective state: to develop natural resources; to develop one's musical talent.
2. to cause to grow or expand: to develop one's muscles.
3. to elaborate or expand in detail: to develop a theory.
4. to bring into being or activity; generate; evolve.
5. Drafting. to transfer the details of (a more or less two-dimensional design, pattern, or the like) from one surface, especially one that isprismatic or cylindrical, onto another, usually planar, in such a way that the distances between points remain the same.
6. Biology:
(a) to cause to go through the process of natural evolution from a previous and lower stage.
(b) to cause to progress from an embryonic to an adult form.
7.Mathematics: to express in an extended form, as in a series.