Science Grade 6Chapter 5: Cycles in the Biosphere : Science Grade 6Chapter 5: Cycles in the Biosphere Lesson 2: How Do Nitrogen and Water Cycle? Page B14
Nitrogen : Nitrogen Nearly 80% of Earth’s atmosphere consists of Nitrogen gas.
Living things need nitrogen to form proteins
However, living things can’t use the form of nitrogen up in the atmosphere
Nitrogen Fixation is the process of nitrogen gas changing into usable nitrogen compounds
Who helps with Nitrogen Fixation? : Who helps with Nitrogen Fixation? Lightning is responsible for some nitrogen fixation
The energy from the lightning combines oxygen and nitrogen in the air, where they dissolve in the rainwater
Special bacteria is responsible for most of the nitrogen fixation. These bacteria either live on plants or in soil or water.
Nitrogen Cycle on B15 : Nitrogen Cycle on B15 1) Nitrogen fixation by lightning or bacteria
2) Nitrogen is in the soil
3) Plants get nitrogen
4) Animals eat plants
5) Animals excrete waste and nitrogen returns to back to soil
6) Animals and Plants die and decomposers will break them down to return the nitrogen back to soil
7) Other bacteria change the nitrogen back into gas.
Slide 5 :
Disruption of Nitrogen Cycle : Disruption of Nitrogen Cycle Humans can either cause shortage or surplus of usable nitrogen in soil. How?
When crops are harvested, the nitrogen in plant leaves the soil and does not return (Shortage)
Erosion and Irrigation can wash nitrogen out of the soil (Shortage)
Erosion : Erosion
Erosion : Erosion
Irrigation : Irrigation
Irrigation : Irrigation
Disruption of Nitrogen Cycle : Disruption of Nitrogen Cycle Human activities cause increased nitrogen deposition (surplus) in a variety of ways, including:
burning of both fossil fuels and forests, which releases nitrogen into the atmosphere
fertilizing crops with nitrogen-based fertilizers, which then enter the soil and water. Or planting plants that support nitrogen-fixing bacteria
ranching, during which livestock waste releases ammonia into the soil and water
allowing sewage to leach into streams, rivers, and groundwater
What are consequences of Nitrogen Surplus? : What are consequences of Nitrogen Surplus? Acid Rain (Nitric Acid)
Ruining Water Quality
Affect on Marine Life
Too much nitrogen in soil can kill plants!
Water : Water Earth is ¾ covered with water!
97% of this ¾ is salty
The remaining 3%, less than 1% is usable fresh water
The water is not spread evenly around Earth
Therefore people have to bring in water to places that need it, such as the desert, or farms (irrigation)
Most of our drinking water come from rivers, lakes or wells
Water Cycle B17 : Water Cycle B17 Water bodies (sea, oceans, lakes and rivers) lose water by evaporation (from liquid to gas)
Plants lose water by transpiration
Animals lose water by perspiration (sweating)
The water vapor in the atmosphere forms clouds by condensation (from gas to tiny drops of liquid)
When clouds are heavy with liquid the water falls as precipitation (rain, sleet, snow or hail)
Slide 15 :
Disruption of Water Cycle : Disruption of Water Cycle Pollution (water cycle still continues but our water is not drinkable!)
Deforestation (less plants less transpiration less precipitation)