2. Biological,
chemical, and physical properties of matter result from the ability of atoms to
form bonds from electrostatic forces between electrons and protons and between
atoms and molecules. As a basis for understanding this concept:
a. Students
know atoms combine to form molecules by sharing electrons to form covalent
or metallic bonds or by exchanging electrons to form ionic bonds.
b. Students
know chemical bonds between atoms in molecules such as H2, CH4,
NH3, H2CCH2, N2, Cl2,
and many large biological molecules are covalent.
c. Students
know salt crystals, such as NaCl, are repeating patterns of positive and
negative ions held together by electrostatic attraction.
7. Each element
on Earth moves among reservoirs, which exist in the solid earth, in oceans, in
the atmosphere, and within and among organisms as part of biogeochemical
cycles. As a basis for understanding this concept:
a. Students
know the carbon cycle of photosynthesis and respiration and the nitrogen
cycle.
b. Students
know the global carbon cycle: the different physical and chemical forms of
carbon in the atmosphere, oceans, biomass, fossil fuels, and the movement of
carbon among these reservoirs.
c. Students
know the movement of matter among reservoirs is driven by Earth's internal
and external sources of energy.
6. Stability in
an ecosystem is a balance between competing effects. As a basis for
understanding this concept:
a. Students
know biodiversity is the sum total of different kinds of organisms and is
affected by alterations of habitats.
b. Students
know how to analyze changes in an ecosystem resulting from changes in
climate, human activity, introduction of nonnative species, or changes in
population size.
d. Students
know how water, carbon, and nitrogen cycle between abiotic resources and
organic matter in the ecosystem and how oxygen cycles through photosynthesis
and respiration.
e. Students
know a vital part of an ecosystem is the stability of its producers and decomposers.