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Environmental Science Ch. 3&5:

How Ecosystems Work

The Gulf of Mexico’s

Dead Zone

The Gulf of Mexico’s

Dead Zone

•Nutrient-rich runoff causes plankton blooms

and hypoxia—low oxygen levels—in the Gulf of

Mexico.

•Hypoxia kills or displaces marine organisms,

causing a decline in the fisheries and the

fishing industry.

•U.S. government and farmers debate the need

to cut down on fertilizer use.

•Nutrient-rich runoff causes plankton blooms

and hypoxia—low oxygen levels—in the Gulf of

Mexico.

•Hypoxia kills or displaces marine organisms,

causing a decline in the fisheries and the

fishing industry.

•U.S. government and farmers debate the need

to cut down on fertilizer use.

Talk About It Do you think the distance between the source of the nitrogen and phosphorus and the dead zones themselves makes it difficult to manage this problem? Why or why not?

Talk About It Do you think the distance between the source of the nitrogen and phosphorus and the dead zones themselves makes it difficult to manage this problem? Why or why not?

POSITIVE FEEDBACK LOOPSPOSITIVE FEEDBACK LOOPS

Positive feedback loops can help erosion turn a fertile

field to desert in just a few years.

Positive feedback loops can help erosion turn a fertile

field to desert in just a few years.

Dust storm, Stratford Texas, 1930s

Interacting SystemsInteracting Systems

Lesson 3.2 Systems in Environmental Science

• Inputs into Earth’s interconnected systems include energy, information, and matter.

• Feedback loops regulate systems.

• Negative feedback loops: Result in stabilization of a system

• Positive feedback loops: Result in a system moving to an extreme

Did You Know? Predator-prey cycles are negative feedback loops. If prey populations rise, predator populations can rise in response, causing prey populations to fall. Then predator populations may decline, allowing prey populations to rise again, and so on.

Did You Know? Predator-prey cycles are negative feedback loops. If prey populations rise, predator populations can rise in response, causing prey populations to fall. Then predator populations may decline, allowing prey populations to rise again, and so on.

Negative feedback loop

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Spheres of Function

• Earth can be divided into spheres that are defined

according to their location and function.

1. Hydrosphere – Water

2. Geosphere – The crust and upper mantle

1. Asthenosphere & Lithosphere (Lower mantle)

2. Outer Core

3. Inner Core

3. Atmosphere – All of the gases (air)

4. Biosphere – All of life

Spheres of FunctionSpheres of Function• Earth can be divided into spheres that are defined

according to their location and function.

• Earth can be divided into spheres that are defined

according to their location and function.

Lesson 3.2 Systems in Environmental Science

Ch. 3-3: Energy Flow In Ecosystems

Key Terms• Cellular Respiration

• Consumer

• Decomposer

• Food Web

• Producer

• Trophic Level

Ch. 3 Section 1:Why Do I Need To Know This?

1. Because what you are depends upon what you eat . . . so we need to know what we’re eating and what that stuff is eating.

2. Because we are removing major amounts of organisms from various levels in ecosystems and causing serious disruptionto food webs and food chains.

3. Because we can increase food production to feed more people without using toxic pesticides by understanding the importance of each and every trophic level in an ecosystem.

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Energy Flow In Ecosystems

• All organisms need

energy in order to

survive.

• To fully understand an

organism and its

ecosystem, we need to

understand how it gets

its energy and how the

energy flows in the

ecosystem.

Life Depends on the Sun

• Almost all life depends either directly or indirectly for energy from the sun.

• Plants, algae and some bacteriacan turn solar energy directly into energy through a process called photosynthesis. These organisms are called producers.

• When animals eat plants or other animals that ate plants, they are still getting their energy indirectly from the sun. These organisms are consumers.

An Exception To the Rule: Deep-Ocean Ecosystems

• There is one known exception to the rule about all life depending on the sun, and that is at the very bottom of the deep ocean.

• In 1977, scientists discovered that existed so deep that no sunlight could reach them.

• The scientists discovered that the plants and animals got their energy from volcanoes erupting underneath the ocean!

– They called this type of life chemosynthesis.

What Eats What• Consumers that only eat

producers are called herbivores.

• Consumers that only eat other consumers are called carnivores.

• Consumers that eat both producers and other consumers are called omnivores.

• Consumers that get their nutrients by eating the dead remains of other organisms are called decomposers.

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Respiration: Burning The Fuel• Photosynthesis is the

chemical reaction used by producers to make food.

– The chemical reaction is: 6CO2 + 6 H20 + Light Energy ���� C6H12O6 + 6O2

• Respiration is the process that consumers use to produce energy from the food they eat.

– The chemical reaction is: C6H12O6 + 6O2 ���� 6CO2 +

6H20 + Energy

• They are opposite reactions!

Energy Transfers: Food Chains, Food Webs, and Trophic Levels

• Every time one organism eats another organism, energy is transferred in an ecosystem.

• Ecologists trace the transfer of energy in two ways:

– Food Chains: These show the direct line of how the energy is transferred from one organism to another.

– Food Webs: These show the many feeding relationships between organisms in an ecosystem.

Food Chains and Food Webs

• Food chains are especially useful in showing direct causeand effect relationships in an ecosystem.

• Food webs are useful in representing how an ecosystem truly worksbecause most consumers usually eat more than one organism.

Trophic Levels• Each level of energy transfer in

an ecosystem is known as a trophic level.

• As energy moves up each trophic level, about 90% of the energy is lost, leaving only about 10% of the energy available for the next level.

• Therefore, the lowest trophic levels contain the largestpopulation sizes and the highest trophic levels have the smallest population sizes.

• Energy is lost in each trophic level because all the life functions for the organisms at that level (such as growing, moving, reproducing, etc.).

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How Energy Loss Affects And Ecosystem

• When the amount of energy available at a lower level decreases, the amount of organisms that can be sustained at a higher trophic level also decreases and the number of trophic levels that can exist also decreases.

• Humans are at the top of all trophic levels.

– So, if we wipe out many lower tropic levels, we will reduce the number of people that can live on the planet and can wipe out many species that live at lower trophic levels.

Ch. 3-2: The Cycling of Materials

Key Terms• Precipitation

• Water Cycle

• Carbon Cycle

• Phosphorous Cycle

• Nitrogen Cycle

Ch. 3 Section 4:Why Do I Need To Know This?

1. Because every atom of every cell in your body has most likely been a part of another organism.

2. Because every atom of every molecule of food that you eat or drink has probably been eaten, drunk, or used by another living organism.

3. Because as long as the materials recycle, an ecosystem will stay in balance. When it no longer cycles from organism to organism, the ecosystem will collapse and die out.

Nutrient CyclingNutrient Cycling

•Matter cycles through the

environment.

•Matter can be transformed,

but cannot be created or

destroyed.

•Nutrients, matter that

organisms require for life

process, circulate

throughout the environment

in biogeochemical cycles.

•Matter cycles through the

environment.

•Matter can be transformed,

but cannot be created or

destroyed.

•Nutrients, matter that

organisms require for life

process, circulate

throughout the environment

in biogeochemical cycles.

Lesson 3.4 Biogeochemical Cycles

Did You Know? Organisms require several dozen nutrients, such as nitrogen, phosphorus,

and carbon, to survive.

Did You Know? Organisms require several dozen nutrients, such as nitrogen, phosphorus,

and carbon, to survive.

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The Cycling of Materials• In every ecosystem, all materials

get recycled.

• All materials get recycled at various rates.

– Some are very fast, while others can take millions of years.

• Without the recycling of materials, all ecosystems would collapse when they ran out of limited resources.

• There are many cycles in nature, but 3 of the most important are:

1. The Water Cycle

2. The Carbon Cycle

3. The Nitrogen Cycle

The Water Cycle• Water is essential for all life.

• Although water changes form(from a solid to liquid to gas), the overall amount of water remains the same on the Earth.

• The 3 main steps to the water cycle are:

1. Evaporation

2. Condensation

3. Precipitation

• The overall force driving the water cycle is the energy from the sunsun.

• Water can be removed from the water cycle and stored underground as groundwater.

The Water Cycle

• Carbon is also essential for all life on Earth.

• Carbon is used to make up proteins, fats, and carbohydrates(all of which we need everyday).

• When consumers eat producers, they take in the carbon they need.

• During respiration, consumers give back carbon into the environment.

• Some carbon gets stored underground as the remains of plants and animals get buried. This carbon will go onto become fossil fuels.

The Carbon Cycle

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The Carbon Cycle How Humans Are Affecting The Carbon Cycle

• Fossil fuels, such as coal, oil and gasolinecontain large amounts of carbon that has been stored underground.

• As humans burn fossil fuels, we are emitting large amounts of carbon dioxide into the ecosystem, which is having a major effect on the world’s atmosphere and climate.

• A natural mineral found in nature

• Important nutrient for PLANT growth

• Major Component of fertilizers and man-

made materials

• High potential for Pollution through

– Runoff into streams and Ocean

The Phosphorous Cycle The Phosphorous Cycle

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How Humans Are Affecting The Phosphorous Cycle

• Algae Blooms

• Fish Kills

• Pollution of our

drinking water

The Nitrogen Cycle• Nitrogen is another essential

element for life.• Nitrogen is used to make

proteins, which is necessary for life.

• Although 78% of the atmosphere is Nitrogen, only a special type of Nitrogen called Nitrates (NO3) can be used by most life forms on the planet.

• In order to get Nitrogen, most bacteria depend upon bacteria to “fix” the Nitrogen in the atmosphere to make it useable at Nitrates.

– The bacteria that “fix” the Nitrogen are called Nitrogen-fixing bacteria.

Closing the Nitrogen Cycle• Once Nitrogen enters into the ecosystem

through the nitrogen fixing bacteria, it mostly stays there.

• Nitrogen in an ecosystem gets broken down by decomposers, such as fungi and bacteria.

• However, some Nitrogen is returned to the atmosphere by different bacteria.

The Nitrogen Cycle

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Ch. 3-3: How Ecosystems Change

Key Terms• Climax Community

• Pioneers

• Succession

Ch. 5 Section 4:Why Do I Need To Know This?

1. Because all ecosystems change over time.

2. So that we can understand the role of each

organism in its ecosystem to know how it is

helping the ecosystem change.

3. So that we can better respond to natural

disasters and environmental problems by

using succession to help fix the problem

and restore a damaged ecosystem.

Key Sections Ch. 5-4

• How Ecosystems Change

• Succession

• Secondary Succession

• Fire-Maintained Communities

• Primary Succession

How Ecosystems Change

• All ecosystems change over time.

• Over time, areas will change from a rockylandscape to a very well developed and stablecommunity.

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Succession• Succession is the regular

pattern of change in the species in a community.

• Succession happens because as one species enters into an ecosystem, it alters the ecosystem to suit it.

• As the species change the ecosystem, they make it more difficult for some organisms to live in the ecosystem and easier for others to live in it.

• Eventually, an ecosystem reaches a stable and finalcommunity. This is called a climax community.

Primary Succession

• Primary succession occurs on surfaces where no previous ecosystem existed.

– This is much slower process than secondary succession, typically taking thousands of years to happen.

• The first organisms to move into the new area are called pioneers. Bacteria and lichens are two common pioneers.

– The pioneers play an important role in succession because they turn raw material into useable resources for all species that follow them.

Primary SuccessionPrimary Succession• Occurs when there are no traces of the original

community remaining, including vegetation and soil

• Pioneer species, such as lichens, are the first to

colonize.

• The environment changes as new species move in,

adding nutrients and generating habitat.

• Occurs when there are no traces of the original

community remaining, including vegetation and soil

• Pioneer species, such as lichens, are the first to

colonize.

• The environment changes as new species move in,

adding nutrients and generating habitat.

Secondary Succession• Secondary succession occurs

when a new community develops on the spot of a previously existing community.

• This typically happens after a major natural disaster (such as a fire) or after an area has been cleared for human use.

• Secondary succession happens rather rapidly (within about 150years) because the soil and many of the necessary nutrients are already in place.

• During secondary succession, grasses and flowers recover first. Then, over time, shrubs and trees move in, and finally trees take over, crowding out the plants and shrubs.

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Secondary Succession

• Occurs when a disturbance dramatically alters a

community but does not completely destroy it

• Common after disturbances such as fire, logging, or

farming

• Occurs significantly faster than primary succession

• Occurs when a disturbance dramatically alters a

community but does not completely destroy it

• Common after disturbances such as fire, logging, or

farming

• Occurs significantly faster than primary succession

Fire-Maintained Communities• Many ecosystems depend upon

natural fires to maintain themselves.

• Some species, pine trees, for example, require the heat from a fire to release their seeds.

• Many animals depend on natural fires to open up space for grassesand other producers to grow in order to feed upon them.

• Fire helps to eliminate newspecies to the ecosystem to help maintain the stability of that ecosystem.

• As a result, in some areas, firefighters allow naturally occurring fires to burn themselves out.

Succession in WaterSuccession in Water• Primary aquatic succession occurs when an

area fills with water for the first time.

• Disturbances such as floods or excess

nutrient runoff can lead to secondary aquatic

succession.

• Primary aquatic succession occurs when an

area fills with water for the first time.

• Disturbances such as floods or excess

nutrient runoff can lead to secondary aquatic

succession.

Climax CommunitiesClimax Communities• Ecologists once thought

succession leads to

stable “climax”

communities.

• Today, ecologists see

communities as

temporary, ever-

changing associations

of species.

• Communities are

influenced by many

factors and constant

disturbances.

• Ecologists once thought

succession leads to

stable “climax”

communities.

• Today, ecologists see

communities as

temporary, ever-

changing associations

of species.

• Communities are

influenced by many

factors and constant

disturbances.

Beech-maple forest, a classic “climax community”

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Ecological DisturbancesEcological Disturbances• A community in equilibrium is generally stable and balanced, with most populations at or around carrying capacity.

• Disturbances or changes in the environment can throw a community into disequilibrium.

• Severe disturbances can cause permanent changes to a community and initiate a predictable series of changes called succession.

• A community in equilibrium is generally stable and balanced, with most populations at or around carrying capacity.

• Disturbances or changes in the environment can throw a community into disequilibrium.

• Severe disturbances can cause permanent changes to a community and initiate a predictable series of changes called succession.

Forest fire

Black and White, and Spread

All Over

Black and White, and Spread

All Over

• Zebra mussels and quagga mussels were accidentally

introduced into Lake St. Clair in the late 1980s.

• They have since spread throughout the Great Lakes

system and connecting rivers.

• The invasive mussels have a high economic and ecological cost.

• Zebra mussels and quagga mussels were accidentally

introduced into Lake St. Clair in the late 1980s.

• They have since spread throughout the Great Lakes

system and connecting rivers.

• The invasive mussels have a high economic and ecological cost.

Talk About It The Great Lakes are home to more than 20 native mussel species. Why are the zebra and

quagga mussels so much more destructive than the

lakes’ native mussels?

Talk About It The Great Lakes are home to more than 20 native mussel species. Why are the zebra and

quagga mussels so much more destructive than the

lakes’ native mussels?

Invasive SpeciesInvasive Species•Nonnative organisms that spread

widely in a community

•A lack of limiting factors such as

predators, parasites, or competitors

enables their population to grow

unchecked.

•Not all invasive species are harmful.

•Nonnative organisms that spread

widely in a community

•A lack of limiting factors such as

predators, parasites, or competitors

enables their population to grow

unchecked.

•Not all invasive species are harmful.

Did You Know? Although the European honeybee is

invasive to North America, it is beneficial because it

pollinates our agricultural crops.

Did You Know? Although the European honeybee is

invasive to North America, it is beneficial because it

pollinates our agricultural crops.