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A. Diversity of Life
By the end of 12th grade, students should know that:
- The variation of organisms within a species increases the likelihood that at least some members of the species will survive under changed environmental conditions, and a great diversity of species increases the chance that at least some living things will survive in the face of large changes in the environment.
- The degree of kinship between organisms or species can be estimated from the similarity of their DNA sequences, which often closely matches their classification based on anatomical similarities.
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B. Heredity
By the end of 12th grade, students should know that:
- Some new gene combinations make little difference, some can produce organisms with new and perhaps enhanced capabilities, and some can be deleterious.
- The sorting and recombination of genes in sexual reproduction results in a great variety of possible gene combinations from the offspring of any two parents.
- The information passed from parents to offspring is coded in DNA molecules.
- Genes are segments of DNA molecules.
- Gene mutations can be caused by such things as radiation and chemicals.
- The many body cells in an individual can be very different from one another, even though they are all descended from a single cell and thus have essentially identical genetic instructions.
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C. Cells
By the end of 12th grade, students should know that:
- Every cell is covered by a membrane that controls what can enter and leave the cell.
- Within every cell are specialized parts for the transport of materials, energy transfer, protein building, waste disposal, information feedback, and even movement.
- The work of the cell is carried out by the many different types of molecules it assembles, mostly proteins.
- The genetic information encoded in DNA molecules provides instructions for assembling protein molecules.
- Complex interactions among the different kinds of molecules in the cell cause distinct cycles of activities, such as growth and division.
- Gene mutation in a cell can result in uncontrolled cell division, called cancer.
- Most cells function best within a narrow range of temperature and acidity.
- A living cell is composed of a small number of chemical elements mainly carbon, hydrogen, nitrogen, oxygen, phosphorous, and sulfur.
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D. Interdependence of Life
By the end of 12th grade, students should know that:
- Ecosystems can be reasonably stable over hundreds or thousands of years.
- Like many complex systems, ecosystems tend to have cyclic fluctuations around a state of rough equilibrium.
- Human beings are part of the earth's ecosystems.
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E. Flow of Matter and Energy
By the end of 12th grade, students should know that:
- At times, environmental conditions are such that plants and marine organisms grow faster than decomposers can recycle them back to the environment.
- The amount of life any environment can support is limited by the available energy, water, oxygen, and minerals, and by the ability of ecosystems to recycle the residue of dead organic materials.
- The chemical elements that make up the molecules of living things pass through food webs and are combined and recombined in different ways.
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F. Evolution of Life
By the end of 12th grade, students should know that:
- The basic idea of biological evolution is that the earth's present-day species developed from earlier, distinctly different species.
- Molecular evidence substantiates the anatomical evidence for evolution and provides additional detail about the sequence in which various lines of descent branched off from one another.
- Natural selection provides the following mechanism for evolution: Some variation in heritable characteristics exists within every species, some of these characteristics give individuals an advantage over others in surviving and reproducing, and the advantaged offspring, in turn, are more likely than others to survive and reproduce.
- Heritable characteristics can be observed at molecular and whole-organism levels in structure, chemistry, or behavior.
- New heritable characteristics can result from new combinations of existing genes or from mutations of genes in reproductive cells.
- Natural selection leads to organisms that are well suited for survival in particular environments.
- The theory of natural selection provides a scientific explanation for the history of life on earth as depicted in the fossil record and in the similarities evident within the diversity of existing organisms.
- Life on earth is thought to have begun as simple, one-celled organisms about 4 billion years ago.
- Evolution builds on what already exists, so the more variety there is, the more there can be in the future.
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