University:
High School
Course:
High School Botany
Academic year:

2019
Views:

453

Pages:

22
Author:

larbiwxcvbn

Ecosystem Cycling Essential Questions 1. Describe how where water is found and how it is transferred between the biotic and abiotic factors in an ecosystem. 2. Describe how where carbon is found and how it is transferred between the biotic and abiotic factors in an ecosystem. 3. Describe how where nitrogen is found and how it is transferred between the biotic and abiotic factors in an ecosystem. 4. Identify the role of decomposers in both the carbon and nitrogen cycles. Biogeochemical Cycles • Biogeochemical cycle – the cycle of chemical nutrients between the living & non-living components of an ecosystem – Bio = life, Geo = Earth • Biotic – living • Abiotic – non-living – Example: Water, air, rocks How Biogeochemical Cycles Work • Chemical nutrients move between the biotic and abiotic components of an ecosystem – Storage reservoirs – biotic or abiotic components where nutrients are found • The boxes in the diagram – Processes – chemical processes that convert nutrients from one chemical form to another • Represented by the numbers in the diagram Where Nutrients are Found (Storage Reservoirs) • Types of Storage Reservoirs: – Biosphere – organisms (biotic factors) – producers, consumers & decomposers – Geosphere – the Earth (abiotic factor) – rocks, etc – Hydrosphere – water (abiotic factor) – Atmosphere – gases surrounding the Earth General Cycle Description • Chemical nutrients are stored in abiotic reservoirs & are available to producers – Some nutrients have to be chemically altered first • Producers convert nutrients into an organic form – These can be used by organisms directly • Consumers eat producers • Both producers & consumers produce nutrient waste, which may return to the abiotic reservoir • Decomposers break down the remaining nutrients & return them to abiotic reservoirs Water • Water is crucial to all life on Earth • Organisms need water for: – Maintaining homeostasis – Dissolving & transporting nutrients – A place to live (aquatic organisms) The Water Cycle • Where water is found (storage reservoirs): – Atmosphere – Surface water: ocean, lakes, rivers, ponds, etc – Groundwater: underground lakes & rivers – Organisms The Water Cycle • Processes of the Water Cycle: – Evaporation – water is converted from liquid to gas form • Surface water  atmosphere – Transpiration – water evaporates from plants • Plants  atmosphere – Precipitation – rain, snow, sleet, hail, etc • Atmosphere  groundwater – Run-off – water flow due to gravity • Surface water & groundwater  ocean Human Activity & the Water Cycle • Many human activities affect the water cycle: – Erosion from coastal developments increase silt & decrease visibility & the penetration of sunlight – Chemical pollutants from agricultural and industrial activities travel in surface water & often end up in groundwater & finally in the ocean – Airborne pollutants, such as sulfur dioxide & nitrogen oxides combine with water vapor in the atmosphere to form acid rain – Deforestation decreases the rate of transpiration – Irrigation utilizes the largest portion of freshwater resources & is often pumped from groundwater supplies – Global warming has far reaching effects on precipitation patterns Carbon • Carbon is the major component of all organic molecules • Carbon cycles through ecosystems in two main forms: – Carbon dioxide (CO2) – Organic molecules (carbohydrates, lipids, proteins & nucleic acids) The Carbon Cycle • Where Carbon is Found: – Atmosphere – as CO2 – Biosphere (organisms) – as organic molecules – Fossil fuels – as hydrocarbons The Carbon Cycle • Processes: – Photosynthesis – converts CO2 into organic molecules • Atmosphere  biosphere – Cellular respiration – converts organic molecules into ATP, CO2 is a bi-product • Biosphere  atmosphere – Decomposition – breaks down organic molecules • Biosphere  atmosphere – Combustion (burning) – converts organic molecules into CO2 • Fossil fuels  atmosphere Human Impact on the Carbon Cycle • • On a global scale the amount of CO2 returned to the atmosphere through cellular respiration closely balances its removal by photosynthesis Combustion of fossil fuels by humans are adding CO2 to the atmosphere at a much higher rate Nitrogen • Nitrogen is a major component of proteins & nucleic acids – It is essential to the structure & functioning of all living organisms • Nitrogen cycles through ecosystems in many forms: – – – – Atmospheric nitrogen (N2) Ammonia (NH3) Ammonium ions (NH4+) Nitrates (NO3-) The Nitrogen Cycle • Where Nitrogen is Found: – Atmosphere – as N2 – Soil – Organisms • Organisms cannot directly use atmospheric nitrogen (N2) – It has to be converted to a useful form (“nitrogen fixation”)! – This is done by bacteria in the soil! The Nitrogen Cycle • Processes: – Nitrogen Fixation – converts atmospheric nitrogen to a useful form • Atmosphere  Geosphere (soil) • KNOW THIS PROCESS!! – Assimilation – plants absorb nitrogen compounds from the soil • Geosphere  biosphere – Decomposition – decomposers break down decaying organisms & return nitrogen to the soil • Biosphere  geosphere – Denitrification – bacteria convert nitrogen in the soil into atmospheric nitrogen (N2) • Geosphere  atmosphere Human Activities & the Nitrogen Cycle • Human activities disrupt the nitrogen cycle by adding more nitrogen to the biosphere than natural processes – Combustion of fossil fuels release stored nitrogen – Agricultural practices often use large amounts of synthetic nitrogen fertilizer • Less than half of the applied fertilizer is used by plants • Both processes release nitrous oxide (N2O) which is a greenhouse gas Nutrient Pollution • Nutrient pollution occurs when human activities add excess amounts of chemical nutrients into aquatic ecosystems – Sources of phosphate & nitrate pollution: • Agricultural fertilizers & runoff from livestock waste • Dishwasher detergents (PO43- only) • Outflow from sewage treatment facilities Cultural Eutrophication • Excess plant nutrients (phosphate & nitrate) in aquatic ecosystems encourages algal blooms • As the algae die, they sink to the bottom & are consumed by decomposing bacteria • These decomposing bacteria use up the oxygen dissolved in the water • This oxygen depletion results in the die off of other aquatic organisms Dead Zones • Cultural eutrophication can lead to large areas of “dead zones” where not much aquatic life can survive • Example: – Runoff from Midwestern farm fields drains into the Mississippi River & is carried into the Gulf of Mexico – This leads to an annual summer dead zone Essential Questions 1. Describe how where water is found and how it is transferred between the biotic and abiotic factors in an ecosystem. 2. Describe how where carbon is found and how it is transferred between the biotic and abiotic factors in an ecosystem. 3. Describe how where nitrogen is found and how it is transferred between the biotic and abiotic factors in an ecosystem. 4. Identify the role of decomposers in both the carbon and nitrogen cycles.