environmental science

ENVIRONMENTAL SCIENCE 13e

CHAPTER 3:Ecosystems: What Are They and How Do They Work?

Rainforest

• http://www.youtube.com/watch?v=Ws6m46AAbQQ

Core Case StudyIn class assignment

• Tropical Rainforests are Disappearing• Where are tropical rainforests found?• How much of the earth’s land surface do they cover?

Studies indicate they contain up to ______ of the world’s known terrestrial plant and animal species

• Define ecosystems• About ________ of these forests have been destroyed by

humans

Core Case Study: Tropical Rainforests Are Disappearing (2)

• Consequences of disappearing tropical rainforests1. __________ as species become extinct

2. ______________: fewer trees to remove carbon dioxide from the atmosphere

3. _______________: can lead to increase in tropical grasslands

• Define Ecological Tipping Point-

• What is the ecological tipping point for this case study?

Fig. 3-1, p. 39

Satellite image of the loss of tropical rain forest near the Bolivian City of Santa Cruz. Why is this an example of Natural Capital degradation?

June 1975 May 2003

3-1 What Keeps Us and Other Organisms Alive?

• Concept 3-1A The four major components of the earth’s life-support system are the atmosphere (air), the hydrosphere (water), the geosphere (rock, soil, sediment), and the biosphere (living things).

• Concept 3-1B Life is sustained by the flow of energy from the sun through the biosphere, the cycling of nutrients within the biosphere, and gravity.

Earth Has Four Major Life-Support Components

• Atmosphere

• Hydrosphere

• Geosphere

• Biosphere

Fig. 3-2, p. 41

RockCrust

Atmosphere

Vegetationand animals

Biosphere

Mantle

Lithosphere

Soil

Geosphere(crust, mantle, core)

Mantle

Core

Crust(soil and rock)

Biosphere(living organisms)

Atmosphere(air)

Hydrosphere(water)

Three Factors Sustain Life on Earth

1) One-way flow of high-quality energy from the sun

2) Cycling of matter or nutrients through parts of the biosphere

3) Gravity

Solar Energy Reaching the Earth

• Electromagnetic waves– Visible light

– UV radiation

– Heat

• Natural greenhouse effect

• Energy in = energy out

• Human-enhanced global warming

Solarradiation

Radiated byatmosphereas heat

Reflected byatmosphere

Mostabsorbedby ozone

Absorbedby the earth

Greenhouseeffect

Visiblelight

UV radiation

Heat radiatedby the earthHeat

Troposphere

Lower Stratosphere(ozone layer)

Fig. 3-3, p. 41

Greenhouse Effect Animation

• http://www.youtube.com/watch?v=CxUK2TizQ4g&feature=related

3-2 What Are the Major Components of an Ecosystem?

• Concept 3-2 Some organisms produce the nutrients they need, others get the nutrients they need by consuming other organisms, and some recycle nutrients back to producers by decomposing the wastes and remains of organisms.

Ecology

• How organisms interact with biotic (pertaining to life) and abiotic environment (non-living)

• Focuses on specific levels of matter:– Organisms– Populations– Communities– Ecosystems – Biosphere

Smallest unit of a chemical element that exhibits its chemical properties

Atom

Molecule Chemical combination of two or more atoms of the same or different elements

CellThe fundamental structural and functional unit of life

Organism An individual living being

Population A group of individuals of the same species living in a particular place

Community Populations of different species living in a particular place, and potentially interacting with each other

Stepped Art

Ecosystem A community of different species interacting with one another and with their nonliving environment of matter and energy

Biosphere Parts of the earth's air,water, and soil where life is found

Fig. 3-4, p. 42

_______________________________

Which 5 levels does ecology focus on?

Living and Nonliving Components (1)

• Abiotic – Water

– Air

– Nutrients

– Solar energy

– Rocks

– Heat

Living and Nonliving Components (2)

• Biotic– Plants

– Animals

– Microbes

– Dead organisms

– Waste products of dead organisms

Soluble mineralnutrients

Producers

Decomposers

Secondaryconsumer(fox)

Carbon dioxide (CO2)

Primaryconsumer(rabbit)

Producer

Oxygen (O2)Precipitation

Water

Fig. 3-5, p. 43

Trophic Levels (feeding levels)(1)

• Producers – autotrophs–Photosynthesis

• Consumers – heterotrophs– Primary - herbivores– Secondary - carnivores– Third-level (tertiary)– quartenary

• Omnivores

Trophic Levels (2)

• Decomposers (ex. bacteria and fungi)

– Release nutrients from the dead bodies of plants and animals

• Detrivores (ex. earthworms, some insects, vultures)

– Feed on the waste or dead bodies of organisms

Time progression Powder broken down by

decomposers into plantnutrients in soil

MushroomWoodreducedto powder

Dry rotfungus

Termite andcarpenterant work

DecomposersDetritus feeders

Carpenterant galleriesBark beetle

engravingLong-hornedbeetle holes

Fig. 3-6, p. 44

Production and Consumption of Energy

• Photosynthesis• Carbon dioxide + water + solar energy

glucose + oxygen

6CO2 + 6H2O + solar E C6H12O6 + 6O2

• Aerobic respiration (opposite)

• Glucose + oxygen carbon dioxide + water + energy

Energy Flow and Nutrient Recycling

• Ecosystems sustained through:– One-way energy flow from the sun

– Nutrient recycling

Abiotic chemicals(carbon dioxide,

oxygen, nitrogen,minerals)

Decomposers(bacteria, fungi)

Consumers(herbivores,carnivores)

Producers(plants)

Solarenergy

Heat

Heat Heat

Heat Heat

Fig. 3-7, p. 45

Main components ofan ecosystem

3-3 What Happens to Energy in an Ecosystem?

• Concept 3-3 As energy flows through ecosystems in food chains and webs, the amount of chemical energy available to organisms at each succeeding feeding level decreases.

Energy Flow in Ecosystems

• Trophic levels

• Food chain – Sequence of organisms, each of which

serves as a source of food for the next

• Food web – Network of interconnected food chains

– More complex than a food chain

Fourth TrophicLevel

Third TrophicLevel

Second TrophicLevel

First TrophicLevel

Heat

Heat

HeatHeatHeat

Tertiaryconsumers

(top carnivores)

Secondaryconsumers(carnivores)

Primaryconsumers(herbivores)

Producers(plants)

Solarenergy

Heat

Heat

Decomposers and detritus feeders

Fig. 3-8, p. 46

Food chain

Humans

Squid

Herbivorouszooplankton

Phytoplankton

Krill

Fish

Petrel

Adeliepenguin

Sperm whale

Emperorpenguin

Leopardseal

Killerwhale

Crabeaterseal

Elephantseal

Blue whale

Carnivorousplankton

Fig. 3-9, p. 46

AntarcticFood Web

Usable Energy by Trophic Level

• Energy flow follows the second law of thermodynamics – energy lost as heat

• Biomass decreases with increasing trophic level

• Ecological efficiency – typically 10%

• Pyramid of energy flow

Tertiaryconsumers(human)

Secondaryconsumers(perch)

Producers(phytoplankton)

Primaryconsumers(zooplankton)

Usable energy availableat each trophic level

(in kilocalories)

HeatDecomposers

10

100

1,000

10,000

Heat

Heat

Heat

Heat

Fig. 3-10, p. 47

What happens to amount of usable energy as you go up each level?

Two Kinds of Primary Productivity

• Gross primary productivity (GPP): the rate at which an ecosystems producers convert solar E into chemical E in the form of biomass found in their tissues

• Net primary productivity (NPP)- rate at which producer’s use photosynthesis to produce and store chemical E minus the rate at which they use some of this stored E thru aerobic respiration

• Planet’s NPP limits number of consumers• Humans use, waste, or destroy 10-55% of earth’s total

potential NPP• Human population is less than 1% of total biomass of

earth’s consumers

Temperate forest

Aquatic Ecosystems

Open ocean

Continental shelfLakes and streams

Estuaries

Terrestrial Ecosystems

Extreme desert

Desert scrub

Tundra (arctic and alpine)

Temperate grasslandWoodland and shrubland

Agricultural landSavanna

Northern coniferous forest (taiga)

Swamps and marshesTropical rain forest

Fig. 3-11, p. 48

Average net primary productivity (kcal/m2/yr)

800 1,600 2,400 3,200 4,000 4,800 5,600 6,400 7,200 8,000 8,800 9,600

3-4 What Happens to Matter in an Ecosystem?

• Concept 3-4 Matter, in the form of nutrients, cycles within and among ecosystems and in the biosphere, and human activities are altering these chemical cycles.

Biogeochemical Cycles

• Nutrient cycles• Reservoirs- temporary storage sites for nutrients

• Connect all organisms through time

Hydrologic Cycle

• Water cycle is powered by the sun1. Evaporation

2. Precipitation

3. Transpiration - evaporates from plant surfaces

• Water vapor in the atmosphere comes from the oceans – 84%

• Over land, most of water reaching the atmosphere comes from transpiration

Increasedfloodingfrom wetlanddestruction

Condensation

Evaporationfrom ocean

Climatechange

Infiltrationand percolationinto aquifer

Condensation

Ocean

Lakes andreservoirs

Ice andsnow

Surfacerunoff

Surface runoff

Aquiferdepletion fromoverpumping

Pointsourcepollution

Reduced recharge ofaquifers and floodingfrom covering land with crops and buildings

Groundwatermovement (slow)

Runoff

Precipitationto land

Precipitationto ocean

Transpirationfrom plants

Evaporationfrom land

Fig. 3-12, p. 49

Processes

Processes affected by humans

Reservoir

Pathway affected by humans

Natural pathway

Science Focus: Water’s Unique Properties (1)

• Holds water molecules together – hydrogen bonding

• Liquid over a wide temperature range

• Changes temperature slowly

• Requires large amounts of energy to evaporate

Science Focus: Water’s Unique Properties (2)

• Dissolves a variety of compounds

• Filters out UV light from the sun

• Adheres to a solid surface – allows capillary action in plants

• Expands as it freezes

Carbon Cycle

• Based on carbon dioxide (CO2)• CO2 makes up 0.038% of atmosphere

volume • Major cycle processes

– Aerobic respiration– Photosynthesis– Fossil fuel combustion and deforestation

• Fossil fuels add CO2 to the atmosphere and contribute to global warming

Respiration

Forest fires

Deforestation

Diffusion

Carbon dioxidedissolved in ocean

Carbonin limestone or

dolomite sediments

Marine food websProducers, consumers,

decomposers

Transportation

Carbon dioxidein atmosphere

Carbonin animals

(consumers)

Plants(producers)

Animals(consumers)

Decomposition

Respiration

Compaction

Carbonin fossil

fuels

Carbonin plants

(producers)

Burningfossil fuels

Photosynthesis

Fig. 3-13, p. 51

Processes

Reservoir

Pathway affected by humans

Natural pathway

Nitrogen Cycle

• Multicellular plants and animals cannot utilize atmospheric nitrogen (N2)

• Nitrogen fixation

• Nitrification

• Ammonification

• Denitrification

Nitrogenin atmosphere

Nitrogenloss to deepocean sediments

Nitrogen oxidesfrom burning fuel

Nitratesfrom fertilizer

runoff anddecomposition

Nitrogenin oceansediments Ammonia

in soil

Volcanicactivity

Electricalstorms Nitrogen

in animals(consumers)

Bacteria

Nitratein soil

Nitrogenin plants

(producers)

Nitrificationby bacteria

Denitrificationby bacteria

Uptake by plantsDecomposition

Fig. 3-14, p. 52

Processes

Reservoir

Pathway affected by humans

Natural pathway

Phosphorus Cycle

• Does not cycle through the atmosphere• Obtained from terrestrial rock

formations• Limiting factor on land and in

freshwater ecosystems• Biologically important for producers

and consumers

Seabirds

Phosphatein shallowocean sediments

Bacteria

Animals(consumers)

Plants(producers)

Runoff

Runoff Runoff

Phosphatesin fertilizer

Phosphatesin mining waste

Phosphatesin sewage

Phosphatedissolved inwater

Erosion

Phosphatein deep ocean

sediments

Oceanfood chain

Platetectonics

Phosphatein rock

(fossil bones,guano)

Fig. 3-15, p. 53

Processes

Reservoir

Pathway affected by humans

Natural pathway

Sulfur Cycle

• Most sulfur stored in rocks and minerals• Enters atmosphere through:

– Volcanic eruptions and processes– Anaerobic decomposition in swamps, bogs,

and tidal flats– Sea spray– Dust storms– Forest fires

Fig. 3-16, p. 54

Refiningfossil fuels

Sulfurin animals

(consumers)

Sulfurin plants

(producers)

Sulfur dioxidein atmosphere

Sulfurin soil, rock

and fossil fuels

Sulfurin oceansediments

Dimethylsulfide

a bacteriabyproduct

Processes

Reservoir

Pathway affected by humans

Natural pathway

Decay

Sulfuric acidand Sulfate

deposited asacid rain

Uptakeby plantsDecay

Mining andextraction

Burningcoal

Smelting

3-5 How Do Scientists Study Ecosystems?

• Concept 3-5 Scientists use field research, laboratory research, and mathematical and other models to learn about ecosystems.

Field Research

• Collecting data in the field by scientists

• Remote sensing devices

• Geographic information systems (GIS)

Laboratory Research

• Simplified model ecosystems– Culture tubes– Bottles – Aquariums– Greenhouses– Chambers with controllable abiotic factors

• How well do lab experiments correspond with the greater complexity of real ecosystems?

Scientific Studies of Ecosystems

• Models– Mathematical

– Computer simulations

• Models need to be fed real data collected in the field- baseline data

• Models must determine relationships among key variables

Baseline Data to Measure Earth’s Health

• Needed to measure changes over time

• Lacking for many ecosystems

• Call for massive program to develop baseline data

Core Case StudyIn class assignment

• Tropical Rainforests are Disappearing• Where are tropical rainforests found? Near equator• How much of the earth’s land surface do they cover? No more than 6%

Studies indicate they contain up to _50%__ of the world’s known terrestrial plant and animal species

• Define ecosystems: communities of organisms interacting with one another and with the physical environment of matter and energy in which they live

• About _half__ of these forests have been destroyed by humans

Core Case Study: Tropical Rainforests Are Disappearing (2)

• Consequences of disappearing tropical rainforests1. Decreased biodiversity as species become

extinct

2. Accelerated global warming: fewer trees to remove carbon dioxide from the atmosphere

3. Changes regional weather patterns: can lead to increase in tropical grasslands

• Ecological tipping point- Point in development of an environmental problem where a threshold level is reached, causing an irreversible shift in the behavior of a natural system.

• What is the ecological tipping point for this case study? Once the tropical rain forests are cleared, local weather patterns change so that rainforests can no longer be supported; areas become much less diverse tropical grasslands