1. Unit #11: Ecology (Part 5) GEOCHEMICAL CYCLES and CHANGES IN ECOSYSTEMS
Ms. Day
AP Biology

2. Biogeochemical Cycles
Chemical elements available only in limited amounts
Movement of essential elements between the biotic and abiotic environment
Decomposition allows these cycles to occur!
Carbon Cycle
Nitrogen Cycle
Phosphorus Cycle
Water Cycle (Hydrological cycle)

4. Carbon Cycle

5. Carbon Cycle

6. Greenhouse Gases CO2= a type of “greenhouse” gas
Builds up along in stratosphere with ozone, methane (CH4) and water (vapor)  other greenhouse gases
Helps warm the Earth
Absorbs/re-emits solar heat (radiation)
Where else does CO2 come from?
Cellular respiration, lightning (fires)

7. Green
house
gases O3
layer

9. Rising Atmospheric CO2

10. Atmospheric Carbon Dioxide
One pressing problem caused by human activities is the rising level of atmospheric carbon dioxide
Caused by burning fossil fuels and deforestation
Coal, oil, natural gas

11. The Greenhouse Effect and Global Warming
The greenhouse effect caused by greenhouse gases keeps Earth’s surface at a habitable temperature (THIS IS A GOOD THING )
Increased levels of atmospheric CO2 are magnifying the greenhouse effect, which is thought to cause global warming and climatic change
increase in average temp of Earth's surface air and oceans since the mid-20th century and its projected continuation.

12. Depletion of Atmospheric Ozone
Life on Earth is protected from damaging effects of UV radiation by a protective layer or ozone molecules (O3) in atmosphere
Satellite studies suggest that the ozone layer has been gradually thinning since 1975
Ozone layer thickness (Dobson units)
350
300
250
200
150
100 50
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
Year (Average for the month of October)
1955

13. Ozone Formation

14. Ozone Breakdown
Destruction of atmospheric ozone probably results from chlorine-releasing pollutants (chloroflorocarbons) produced by human activity
Chlorine atoms O3
Chlorine
Cl2O2
CIO O2
Chlorine from CFCs interacts with ozone (O3), forming chlorine monoxide (CIO) and oxygen (O2).
Sunlight causes Cl2O2 to break down into O2 and free chlorine atoms. The chlorine atoms can begin the cycle again.
Two CIO molecules react, forming chlorine peroxide (Cl2O2).
Sunlight

15. Scientists first described an “ozone hole” over Antarctica in 1985; it has increased in size as ozone depletion has increased
October 1979
October 2000
Allows more UV radiation to hit Earth
Why is this harmful to ALL organisms?
UV radiation is known to mutate DNA

16. Nitrogen Cycle
Nitrogen in the air is N2 but organisms can NOT use this form!!!
Called “denitrification”
NO3-  N2
Called “nitrification”
NH3 N03-
(nitrogen we can use)

17. Human Impacts and Nitrogen cycle
Agricultural effects
Cultivation—turns up soil and increases rate of decomposition of organic matter; Releases more nitrogen
Harvesting removes nitrogen from ecosystem
Adding fertilizers and animal wastes to soil has resulted in doubling globe’s supply of nitrogen
Excess nitrogen leeches into soil and into water biomes and ground water
Algal blooms in lakes speed up eutrophication

18. *
Phosphorus Cycle

19. Water (Hydrological)
Cycle

20. Water Cycle

21. Acid Precipitation
Burning fossil fuels is the main cause of acid precipitation
North American and European ecosystems downwind from industrial regions have been damaged by rain and snow containing nitric and sulfuric acid
North America
Europe
4.3
4.6
4.1
Normal rain = pH ~5.6
Acid rain = pH ~4.5

22. Water and the “Nino” Effect
El Nino and La Nina
A prolonged abnormal warming or cooling (±0.9°F) of surface ocean waters in the tropical Pacific ocean (occurs ~5 years)
part of the Southern Oscillation
see-saw pattern of reversing surface air pressure between the eastern and western tropical Pacific
Warming = El Nino Cooling = La Nina
When pressure is high in eastern tropical Pacific  it is low in western tropical Pacific, and vice-versa.
South American fisherman named this for "The Christ Child," because it comes around Christmas.

25. Effects of El Nino La Nina
El Nino : causes warmer temp’s (warm phase)
Heavy rainfalls (warm air “feeds” thunderstorms)/floods  areas are more wet than normal.
warmer waters and air  less migration  increased competition
affects nutrient turnovers in oceans coastal areas
Less hurricanes
More red tides
La Nina- causes cooler temp’s (cool phase)
droughts
colder/snowy winters
tropical cyclones/hurricanes
El Nino events have increased while La Nina has decreased!