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

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)

Carbon Cycle

Carbon Cycle

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)

Green house gases O3 layer

Rising Atmospheric CO2

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

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.

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

Ozone Formation

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

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

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)

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

* Phosphorus Cycle

Water (Hydrological) Cycle

Water Cycle

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

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.

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!