Benchmark 5F
The Living Environment: Evolution of Life
Grades 9-12, page 125

Life on earth is thought to have begun as simple, one-celled organisms about 4 billion years ago. During the first 2 billion years, only single-cell microorganisms existed, but once cells with nuclei developed about a billion years ago, increasingly complex multicellular organisms evolved.

NSES Content Standard C 
Life Science: Biological evolution
Grades 9-12, page 185
The great diversity of organisms is the result of more than 3.5 billion years of evolution that has filled every available niche with life forms.

NSES Content Standard D
Earth and Space Science: Origin and evolution of the earth system
Grades 9-12, page 190
Evidence for one-celled forms of life--the bacteria--extends back more than 3.5 billion years. The evolution of life caused dramatic changes in the composition of the Earth's atmosphere, which did not originally contain oxygen.