1. Betsy Sanford Lost Mountain Middle School 7th Grade Life Science
Ecology - Cycles
Betsy Sanford
Lost Mountain Middle School
7th Grade Life Science

3. The Water Cycle
What – the recurring flow of water throughout the atmosphere and the biosphere
Who - all living things need water
all forms of water, solid (snow, sleet, hail), liquid water & gas (water vapor)
Where – throughout the biosphere and atmosphere
When – constantly cycling
Why – recycling of water for reuse in chemical reactions in living things
How - changes in temperature cause evaporation, condensation, and precipitation
precipitation collects above ground in lakes, ponds and ice flows
precipitation runs off above ground into rivers, streams and oceans
precipitation collects below ground in aquifer

5. The Nitrogen Cycle
What – the recurring flow of nitrogen throughout the atmosphere and the biosphere
Who – all organisms need nitrogen, but not in gas form (the atmosphere is 78% nitrogen)
Where – needed in the soil wherever plants are growing
When – constantly cycling
Why – recycling of nitrogen for reuse in making proteins and DNA
How – nitrogen gas must be chemically changed into forms plants can use to grow
bacteria in the soil “fix” nitrogen (nitrogen fixation)
plants take nitrogen from the soil and consumers eat plants to get nitrogen
consumers die off and decomposers release nitrogen back into the soil
lighting can “fix” nitrogen also

7. The Carbon Cycle
What – the exchange of carbon back and forth from the environment to living things
Who – all living things are made of carbon; carbon is part of the ocean, the air and even rocks
Where – in the atmosphere as carbon dioxide (CO2) and in molecules such as glucose (C6H12O6)
When – constantly cycling
Why – plants use carbon dioxide to make food and all consumers use food for energy
carbon dioxide is one of the greenhouse gases that blankets the Earth to keep it warm
without this blanket of gases, the Earth would be totally frozen
How – chemical reactions
photosynthesis and cellular respiration
when plants die and are buried for millions of years they become fossil fuels like coal and oil
burning fossil fuels releases carbon dioxide into the atmosphere