Transcript Lesson 6.2 - Cycles

Ecosystems and Their
Interactions
Chapter 6
Lesson 6.2
PA Academic Standards for
Environment & Ecology
Standard 4.6.10.B
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Explain how cycles affect the balance in an
ecosystem.
Describe an element cycle and its role in an
ecosystem.
Explain the consequences of interrupting
natural cycles.
Learning Objectives
• Students will describe an element cycle and its role
in an ecosystem.
• Students will explain the consequences of
interrupting natural cycles.
Theme Outline
Lesson 6.2
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Cycles in an Ecosystem
The Water Cycle
The Carbon Cycle
The Nitrogen Cycle
Cycles in an Ecosystem
• Earth is a closed system
• Matter continuously cycles throughout different
parts of an ecosystem
Major Cycles
Three major cycles
• Water Cycle
• Carbon Cycle
• Nitrogen Cycle
Major Cycles
Three major cycles
• Water Cycle
• Carbon Cycle
• Nitrogen Cycle
The Water Cycle
Worldwide Water Supply
Water water everywhere but…
• Covers 70% of the Earth’s surface.
• Most living things are primarily water.
• Humans are ~65% water.
… the Earth’s water supply is finite
• Finite – a fixed amount.
Which means …
The same amount of water that was on Earth when
the dinosaurs were around, still exists today!!!
The Water Cycle
Processes at work…
• Evaporation
• Liquid water to water vapor
• Condensation
• Water vapor cools and condenses into clouds as
water droplets
• Precipitation
• Water droplets fall to the Earth as rain, sleet, hail,
or snow
• Runoff
• Water runs off into nearby streams, rivers, lakes,
or enters the groundwater
• Infiltration/Percolation
Why is water such an
important substance?
• There is less than 1% of freshwater available on
the surface of the Earth for drinking, bathing, and
cooking.
• Human activities have greatly impacted quality of
freshwater supplies.
Example: pollution from chemical spills, poor wastewater
treatment, agricultural runoff, and septic tank failure
Water Quality Concerns
• Agricultural runoff contains a host of potentially
harmful chemicals and sediments that can easily
enter waterways.
• In Pennsylvania, access to potable drinking water
is not an issue for most.
• However, in other parts of the world, limited
access to safe potable water is a major concern for
populations living along many waterways.
Major Cycles
Three major cycles
• Water Cycle
• Carbon Cycle
• Nitrogen
The Carbon Cycle
Why is carbon important anyway?
• Carbon is the building block for life.
• Carbon is the basis for all organic life.
• Carbon is essential for making …  DNA
 Proteins
 Fats
 Carbohydrates
Where else is carbon found?
• Carbon Dioxide (CO2)
• This greenhouse gas helps maintain heat in the
Earth’s upper atmosphere.
• Carbon reservoirs
• Oceans
• Atmosphere
• Rocks
The Carbon Cycle… simplified
The Carbon Cycle:
Rock and Fossil Fuel Formation
Organic matter
Marine shells
Rocks
Minerals
Wetland Material
Organic Matter
Fossil Fuels
Major Cycles
Three major cycles
• Water Cycle
• Carbon Cycle
• Nitrogen
The Nitrogen Cycle
Nitrogen
• Composes ~79% of the atmosphere
• The atmosphere is a major nitrogen reservoir.
• However, most of the nitrogen in the atmosphere
is not in a usable form so it can not be used by
plants and animals.
Nitrogen is necessary for making…
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DNA
Proteins
Amino Acids
Chlorophyll
The Big 3…
N2
Atmosphere
NO3
NO2
Nitrates
Nitrites
Four major processes…
1) Nitrogen fixation
2) Decay
3) Nitrification
4) Denitrification
Types of Nitrogen Fixation
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Atmospheric fixation
Lightning in the atmosphere breaks up nitrogen
molecules and when combine with oxygen they form
nitrates.
N2  NO3
Atmospheric Nitrogen  Nitrates
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Industrial fixation
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Combines nitrogen in the
atmosphere with hydrogen to
form ammonia
Occurs under pressure and
high temperatures (~600oC)
Product used as fertilizer in
agriculture
N2  NH3
Atmospheric Nitrogen  Ammonia
Fertilizer Labels
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Biological fixation
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Plants and bacteria convert atmospheric
nitrogen into ammonia
N2  NH3
Atmospheric Nitrogen  Ammonia
Soybeans/Legumes Nitrogen fixing
bacteria
Decay
• Nitrogen cycles through food chains like other
elements.
• Nitrogen is found in excreted wastes from
animals.
• Microorganisms break down excretions and dead
animals to form ammonia.
Nitrification
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A process that converts nitrogen, in various forms,
into more usable forms of nitrogen that can be
taken up through the roots of plants.
Convert organic nitrogen into nitrites and
nitrates.
NH3  NO3
Ammonia  Nitrates
Denitrification
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A process preformed by bacteria that live deep in
soils and aquatic sediments under anaerobic
conditions.
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What does it mean when we say anaerobic?
NO3  N2
Nitrates  Atmospheric Nitrogen
The Nitrogen Cycle
Changes to Ecosystems
• Occur more frequently in some ecosystems than
others
• Cycles and processes continue to cycle materials
through ecosystems, even after disturbances
• Ecosystems change in order to meet the conditions
present
Example: regrowth of a forest after forest fires destroy
forest floor (organic matter)