Scope, Sequence, and Coordination

A Framework for High School Science Education

Based on the National Science Education Standards

Fossils and Lithologic Units

Evolution of Life, Bacteria and Algae, and Oxygen in the Atmosphere
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.

Further Description:

The origin of life is based upon the combination of elements to form amino acids, then proteins, and ultimately cells. The Miller experiments involved mixing ingredients identified as components in the early earth’s atmosphere, exposing them to lightning, and forming a sludge of amino acids. This led to a series of experiments attempting to show the formation of more and more complex molecules. Eventually, through laboratory recreations of the proposed atmosphere of the early earth, proteinoids were formed. Proteinoids are round cell-like objects composed of proteins. They grow by adding to each other and dividing. Although proteinoids are not living, their formation and characteristics provided steps in the beginning of life.

Fossils provide some evidence of early life forms, although the record is scanty. Blue-green algae (stromatolites) and bacteria have been clearly identified in this early fossil record. In addition, certain rock forms such as red beds and carbonates provide evidence that the atmosphere of the early earth had very little oxygen.

The process of photosynthesis carried out by some bacteria and the early algae was principally responsible for the earth’s oxygen. Environmental changes, mutations possibly due to UV exposure, sexual reproduction, and the mechanism of natural selection provided for a rapid expansion of species. Life began in water but moved to land.

Evolution is supported by the fossil record, although some aspects of explanationCthe theories used to account for the evolutionary processCare sometimes debated. There is no debate among competent scientists about most of the facts of evolution, only about the theories used to explain it.

Concepts Needed:

Grade 9

Types of fossils, evolution, fossilization, geologic time

Grade 10

Paleozoic, form, function, species, evolution, pre-Cambrian, Cambrian, geologic evidence (red beds, stromatolites, carbonates), lithologic, extinctions

Grade 11

Genus, species, niche, symmetry

Grade 12

Genetic mutation, autotrophs, heterotrophs, temporal evolution

Empirical Laws or Observed Relationships:

Evolution as a process, photosynthesis

Theories or Models:

Origin of life, punctuated equilibrium, natural selection, origin, evolution of hydrosphere and atmosphere

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