Log In | Register

Key Idea: Environmental conditions have changed in the past and continue to change today.

Students are expected to know:

  1. Environmental conditions on earth (such as temperature and amount of rainfall) fluctuate over time, and have changed throughout the history of the earth.
  2. Environmental changes can occur abruptly (such as changes caused by volcanic eruptions, asteroids striking the earth, or a new organism entering an ecosystem), or gradually (such as changes caused by the movement of continents, erosion, or sedimentation).
  3. Over long periods of time, small changes in environmental conditions can add up, resulting in large overall changes in environmental conditions. Examples of this include changes in temperature, precipitation, and concentration of CO2 in the atmosphere. This can lead to significant changes in the environment such as a rise in sea level, a decrease in the size of glaciers, and expansion of deserts.


  1. In writing test items, changes in environmental conditions may include changes in the physical environment (climate, geography), or conditions in the living community (which species are present and how many of each species are present), but students will not be tested on whether they know that the term “environmental conditions” includes both living and non-living factors.