8.P.2.1  Students know:  that all organisms on Earth, including humans, use energy derived from resources provided by the environment.  Earth supplies a variety of natural resources that living things use, change, and reuse.   Some of these resources can be replaced and/or reused in nature; these are renewable resources.   Natural resources that cannot be replaced in nature are nonrenewable. 

• Renewable resources are replaced through natural processes at a rate that is equal to or greater than the rate at which they are being used.  Air, freshwater, soil, living things, and sunlight are renewable resources.  Air can be cleaned and purified by plants during the process  of  photosynthesis  as  they  remove  carbon  dioxide  from  the  air  and  replace  it  with  oxygen.     

• The  water  cycle  allows  Earth’s water to be used over and over within the environment.  Topsoil is formed to replace soil that has been carried away by wind and water (although new soil forms very slowly).  Trees and other new plants grow to replace those that have been cut down or died.  Animals are born to replace animals that have died.  Sunlight, or solar energy, is considered a renewable resource because it will continue to be available for billions of years.  It provides a source of energy for all processes on Earth. 

• Some resources are nonrenewable.  Nonrenewable resources are exhaustible because they are being extracted and used at a much faster rate than the rate at which they were formed.  Fossil fuels (coal, oil, and natural gas), diamonds, metals, and other minerals are nonrenewable.  Fossil fuels exist in a fixed amount and can only be replaced by processes that take millions of years.   

8.P.2.2 Students know:  that natural resources can be depleted or used to the point that they are in effect no longer available.  Conservation measures are necessary for nonrenewable resources because they are known to be in a non-replenishing supply.  If renewable resources are used at an increasing rate so that they cannot be naturally replaced fast enough, they too can be depleted.  

• That freshwater can be depleted because of increased demands for water on account of population shifts.  This results in water not being available or not being sufficient to meet demands.  Soil can be lost because it is left bare of vegetation and allowed to erode depletes the land of the fertile topsoil needed for plant growth in that area.  If living resources, such as trees, are removed without being replanted, this can contribute to environmental changes in the land, air, and water in that area that leads to negative consequences.

• That  as  Earth’s  human  population  grows,  the  need  for  natural  resources  increases. 

• The terms reduce, reuse, recycle are important ways that people can be involved in conservation of natural resources.  Reducing involves making a decision to not use a resource when there is an alternative, such as walking or riding a bicycle rather than traveling in a car.  Reusing involves finding a way to use a resource (or product from a resource) again without changing it or reprocessing it, such as washing a drinking glass rather than throwing away plastic or Styrofoam.  Recycling involves reprocessing a resource (or product from a resource) so that the materials can be used again as another item, such as metals, glass or plastics being remade into new metal or glass products or into fibers. 

• Conservation involves preventing the loss of a resource by way of thoughtful management of it.  Increased human consumption can have long-term consequences.  Since the Industrial Revolution, human activities have resulted in major impacts on air, water, and soil.  Pollution has cumulative ecological effects such as acid rain, global warming, or ozone depletion.