Ecosystems and Their Ecosystems and Their InteractionsInteractions

Chapter 6 Chapter 6

Lesson 6.2Lesson 6.2

PA Academic Standards for PA Academic Standards for Environment & EcologyEnvironment & Ecology

Standard 4.6.10.BStandard 4.6.10.B• Explain how cycles affect the balance in an Explain how cycles affect the balance in an

ecosystem.ecosystem.• Describe an element cycle and its role in an Describe an element cycle and its role in an

ecosystem.ecosystem.• Explain the consequences of interrupting Explain the consequences of interrupting

natural cycles.natural cycles.

Learning ObjectivesLearning Objectives

• Students will describe an element cycle and its role Students will describe an element cycle and its role in an ecosystem.in an ecosystem.

• Students will explain the consequences of Students will explain the consequences of interrupting natural cycles.interrupting natural cycles.

Theme OutlineTheme Outline

Lesson 6.2Lesson 6.2• Cycles in an EcosystemCycles in an Ecosystem• The Water CycleThe Water Cycle• The Carbon CycleThe Carbon Cycle• The Nitrogen CycleThe 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 CycleThe Water Cycle

Worldwide Water Supply

Water water everywhere but…

• Covers 70% of the Earth’s surface.Covers 70% of the Earth’s surface.• Most living things are primarily water.Most living things are primarily water.

• Humans are ~65% 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…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, Water droplets fall to the Earth as rain, sleet, hail,

or snowor snow• Runoff

• Water runs off into nearby streams, rivers, lakes, Water runs off into nearby streams, rivers, lakes, or enters the groundwateror 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 CycleWater Cycle• Carbon CycleCarbon Cycle• NitrogenNitrogen

The Carbon CycleThe 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 … DNADNA

ProteinsProteins FatsFats CarbohydratesCarbohydrates

Where else is carbon found?

• Carbon Dioxide (CO2)

• This greenhouse gas helps maintain heat in the This greenhouse gas helps maintain heat in the Earth’s upper atmosphere.Earth’s upper atmosphere.

• Carbon reservoirs• Oceans• Atmosphere• Rocks

The Carbon Cycle… simplified

The Carbon Cycle: Rock and Fossil Fuel Formation

Organic matterOrganic matterMarine Marine shellsshells

Rocks Minerals

pre

ssur

e

Wetland Wetland MaterialMaterialOrganic Organic MatterMatter

Fossil Fuels

pressure

Major Cycles

Three major cycles• Water CycleWater Cycle• Carbon CycleCarbon Cycle• NitrogenNitrogen

The Nitrogen Cycle

Nitrogen• Composes ~79% of the atmosphereComposes ~79% of the atmosphere• The atmosphere is a major nitrogen reservoir.The atmosphere is a major nitrogen reservoir.• However, most of the nitrogen in the atmosphere However, most of the nitrogen in the atmosphere

is not in a usable form so it can not be used by is not in a usable form so it can not be used by plants and animals.plants and animals.

Nitrogen is necessary for making…

• DNADNA• ProteinsProteins• Amino AcidsAmino Acids• ChlorophyllChlorophyll

The Big 3…

N2

Atmosphere

NO3

Nitrates

NO2

Nitrites

Four major processes…

1) Nitrogen fixation

2) Decay

3) Nitrification

4) Denitrification

Types of Nitrogen Fixation

Atmospheric fixationLightning in the atmosphere breaks up nitrogen

molecules and when combine with oxygen they form nitrates.

NN22 NO NO33Atmospheric Nitrogen Nitrates

Industrial fixation 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

Biological fixation Plants and bacteria convert atmospheric

nitrogen into ammonia

NN22 NH NH33

Atmospheric Nitrogen Atmospheric Nitrogen Ammonia Ammonia

Soybeans/Legumes - Soybeans/Legumes - Nitrogen fixing Nitrogen fixing

bacteriabacteria

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 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.

NHNH33 NO NO33Ammonia Ammonia Nitrates Nitrates

Denitrification A process preformed by bacteria that live deep in

soils and aquatic sediments under anaerobic conditions.

What does it mean when we say anaerobic?

NONO33 N N22

Nitrates Nitrates Atmospheric Nitrogen Atmospheric Nitrogen

The Nitrogen Cycle

Changes to Ecosystems

• Occur more frequently in some ecosystems than Occur more frequently in some ecosystems than othersothers

• Cycles and processes continue to cycle materials Cycles and processes continue to cycle materials through ecosystems, even after disturbancesthrough ecosystems, even after disturbances

• Ecosystems change in order to meet the conditions Ecosystems change in order to meet the conditions presentpresentExample: regrowth of a forest after forest fires destroy Example: regrowth of a forest after forest fires destroy

forest floor (organic matter)forest floor (organic matter)