Ecosystems: What Are They and How Do They
Work?
Chapter 3
Key Concepts
What is ecology?
Major components of ecosystems
Energy flow and matter cycles
Ecosystem studies
Importance of Insects
Ecological Services
Pollination
Pest control
Important roles in biological community
Nature of Ecology What is ecology?
Study of connections in nature
Organisms
Cells
Species
Microbes rule!Benefits Include:Decomposition, nutrient cycling, foods, water purification, digestion, antibiotics
Nature of Ecology
Insects751,000
Protists57,700
Plants248,400
Prokaryotes4,800
Fungi69,000
Other animals281,000
Known species
1,412,000
Species Total?Estimated 3.6 - 100
million
Levels of organization interaction
Animation
See Fig. 3-4, p.42
Levels of Organization
of Matter
Genetic Diversity in One Snail Species
What Sustains Life on Earth? Troposphere: Earth’s
surface to 17km up-78% N, 21% O2
Stratosphere- 17 - 48 km contains ozone layer
Hydrosphere
Lithosphere= crust & upper mantle
Biosphere = Zone of Earth where life is found (skin of the apple)* All parts are interconnected!
Fig. 3-2, p. 41
Fig. 3-2, p. 41
Atmosphere
Biosphere
CrustLower mantle
AsthenosphereUpper mantle
Continentalcrust
Oceaniccrust
LithosphereVegetationand animals
Soil
Rock
Crust (soiland rock)
Atmosphere(air)
Biosphere(living and dead
organisms)
Lithosphere(crust, top of upper mantle)
Hydrosphere(water)
Core
Mantle
What Sustains Life on Earth?
Earth’s Life-Support Systems(3 interconnected factors)
One way flow of high-quality energy
Cycling of matter
Gravity- holds atmosphere, enables movement of chemicals through various spheres
“Energy flows, nutrients cycle.”
Biosphere
Carboncycle
Phosphoruscycle
Nitrogencycle
Watercycle
Oxygencycle
Heat in the environment
HeatHeatHeat
Earth’s Life-Support Systems“Energy flows, nutrients cycle.”
Flow of Solar Energy to and from the Earth
Greenhouse gaseswater vapor, CO2, NO, CH4 , O3
Greenhouse effect-
Heat trapped in the troposphere to warm planet
without natural greenhouse effect life would not be possible.
See Fig. 3-3, p. 41
Heat radiatedby the earth
Solarradiation
Absorbedby ozone
UV radiation
Visiblelight
Absorbedby theearth
Reflected byatmosphere (34%)
Energy in = Energy out
Radiated byatmosphereas heat (66%)
Lower Stratosphere(ozone layer)
Troposphere Greenhouseeffect
Heat
Flow of Solar Energy to and from the Earth
Fig. 3-3, p. 41
Sun to Earth animation
Animation
Why is the Earth so Favorable for Life?
Liquid water
Temperature- Past 3.7 billion years average surface temp. = 50- 68 °F
Gravity
Atmosphere
Coniferous forest Desert Coniferous forest Prairie grassland Deciduous forest
100–125 cm (40–50 in.)75–100 cm (30–40 in.)50–75 cm (20–30 in.)25–50 cm (10–20 in.)below 25 cm (0–10 in.)
Average annual precipitation
4,600 m (15,000 ft.)3,000 m (10,000 ft.)1,500 m (5,000 ft.)
Coastal mountainranges
Sierra NevadaMountains
Great AmericanDesert
RockyMountains
GreatPlains
MississippiRiver Valley
AppalachianMountains
Coastal chaparraland scrub
Major Biomes
Sun
Producers (rooted plants)
Producers (phytoplankton)
Primary consumers (zooplankton)
Secondary consumers (fish)
Dissolvedchemicals
Tertiary consumers
(turtles)
Sediment
Decomposers (bacteria and fungi)
Major Components of Freshwater Ecosystems
Sun
Producer
PrecipitationFalling leaves
and twigs
Producers
Primary consumer(rabbit)
Secondary consumer(fox)
Carbon dioxide (CO2)
Oxygen (O2)
Water
Soil decomposers
Soluble mineral nutrients
Fig. 3-5, p. 43
Major Components of a Field Ecosystem
Matter recycling and energy flow animation
Animation
ABC’s of Ecology(The study of how organisms interact with one another
& their non-living environment)
•A= Abiotic (Non-living)
•B= Biotic (Living)
•C= Cultural (Human Interactions)
Factors Limiting Population Growth
Limiting factor principle- Too much or too little of any abiotic factor can limit or prevent growth of population.
Limiting factors:
Excess water or water shortages for terrestrial organisms
Excess or lack of soil nutrients
Dissolved oxygen for aquatic organisms
Salinity for aquatic organisms
Lower limitof tolerance
Upper limitof tolerance
TemperatureLow High
Abundance of organismsFew
organismsFew
organismsNo
organismsNo
organisms
Zone ofintoleranceZone of
physiological stress
Zone ofintolerance Zone of
physiological stress
Optimum range
Po
pu
lati
on
Siz
e
Range of Tolerance
Factors That Limit Population Growth
Range of tolerance:range of abiotic conditions required for population to survive
Law of tolerance “The existence, abundance and distribution of a species in an ecosystem are determined by whether the levels of one or more physical or chemical factors fall within the range tolerated by that species.”
Consumers: Feeding and Respiration
Decomposers (Fungi & Bacteria) - specialized consumers that breakdown detritus (dead stuff) into inorganic nutrients that can be reused by producers
Omnivores
Detritivores- Decomposers & detritus feeders
Aerobic respirationglucose + oxygen = carbon dioxide + water + ENERGY
MushroomWoodreduced
to powder
Long-hornedbeetle holes
Bark beetleengraving
Carpenterant
galleries
Termite andcarpenter
antwork Dry rot fungus
Detritus feeders Decomposers
Time progression Powder broken down by decomposersinto plant nutrients in soil
Fig. 3-6, p. 44
Detritivores
Decomposers convert organic chemicals to inorganic chemicals that can be used by producers
Fig. 3-7, p. 45
Decomposersbacteria, fungi)
Solarenergy
HeatHeat
Heat Heat
Heat
Abiotic chemicals(carbon dioxide,
oxygen, nitrogen,minerals)
Consumers(herbivores,carnivores)
Producers(plants)
Main Structural Components of an Ecosystem
Linked processes animation
Animation
The role of organisms in an ecosystem
Animation
Fig. 3-14, p. 45
Biodiversity(4 Components)
Examples of Biodiversity
Fig. 3-8, p. 46
First TrophicLevel
Second TrophicLevel
Third TrophicLevel
Fourth TrophicLevel
Producers(plants)
Primaryconsumers(herbivores)
Secondaryconsumers(carnivores)
Tertiaryconsumers
(top carnivores)
Detritivoresdecomposers and detritus feeders)
Solarenergy
Heat
Heat Heat Heat
HeatHeat
Heat
Heat
Model of a Food Chain
Humans
Blue whale Sperm whale
Crabeater seal
Killer whale Elephantseal
Leopardseal
Petrel
Fish Squid
Carnivorous plankton
Krill
Phytoplankton
Herbivorouszooplankton
Emperorpenguin
Fig. 3-9, p. 46
Food Web in the Antarctic
Adéliepenguins
Energy Flow in an Ecosystem Biomass
Ecological efficiency= % of usable energy transferred as biomass from one trophic level to the next (2% - 40%)
10% Rule- assumes 10% ecological efficiency
Pyramid of energy flow
See Fig. 3-10, p. 47
Secondaryconsumers
(perch)
10
100
1,000
10,000Usable energy
available ateach tropic level(in kilocalories)
Heat
Heat
Heat
Heat
Heat
Producers(phytoplankton)
Tertiaryconsumers
(human)
Primaryconsumers
(zooplankton)
Pyramid of Energy Flow
Decomposers
Biomass Productivity
Gross primary productivity (GPP)rate at which producers in an ecosystem convert sun into food
Net primary productivity (NPP)= GPP - Respiration
NPP and populationsNPP limits the number of consumers that can live on earth
Energy lost andunavailable toconsumers
Respiration
Growth and reproduction
Sun
Photosynthesis
Gross primaryproduction
Net primaryproduction(energyavailable toconsumers)
Differences between GPP and NPP
Fig. 3-11, p. 48
Swamps and marshes
Tropical rain forest
Temperate forest
Northern coniferous forest
(taiga)
Savanna
Agricultural land
Woodland and shrubland
Temperate grassland
Tundra (arctic and alpine)
Desert scrub
Extreme desert
Aquatic EcosystemsEstuaries
Lakes and streams
Continental shelf
Open ocean
Terrestrial Ecosystems
800 1,600 2,400 3,200 4,000 4,800 5,600 6,400 7,200 8,000 8,800 9,600
Average net primary productivity (kcal/m2/yr)
Net Primary Productivity in Major Life Zones and Ecosystems
Matter Cycling in Ecosystems: Biogeochemical Cycles
Hydrologic (water) cycle
Carbon cycle
Nitrogen cycle
Phosphorus cycle
Sulfur cycle
PrecipitationPrecipitationto land
Evaporation
EvaporationFromocean
Ocean storage
Condensation
Transpiration
Rain clouds
Infiltration andpercolation
Transpirationfrom plants
Groundwater movement (slow)
Precipitation
Simplified Hydrologic (Water) Cycle
Surface runoff (rapid)
EvaporationFromocean
RapidPrecipitatio
nto ocean
Surface runoff (rapid)
Human Interventions in the Hydrologic Cycle
1. Large withdraw of surface and ground waters
2. Clearing vegetation / wetland destruction - runoff, infiltration, groundwater recharge, flood risk, soil erosion & landslides
3. Pollution - addition of nutrients
Diffusion betweenatmosphere and ocean
Carbon dioxidedissolved inocean water
Marine food websProducers, consumers,
decomposers, detritivores
Marine sediments, includingformations with fossil fuels
Combustion of fossil fuels
The Carbon Cycle (Marine)
sedimentation
uplifting over geologic time
photosynthesis aerobic respiration
death, sedimentation
incorporation into
sediments
Atmosphere(most carbon is in carbon dioxide)
Terrestrialrocks
Land food websProducers, consumers,decomposers, detritivores
Peat,fossil fuels
Soil water(dissolved carbon)
Combustionof fossilfuels
volcanic action
The Carbon Cycle (Terrestrial)
photosynthesis
death, burial, compaction over geologic time
aerobic respiration
deforestaion
combustion of wood (for
clearing land; or fuel)
weathering
leaching, runoff
Fig. 3-26, p. 56
Highprojection
Lowprojection
Human Interferences in the Global Carbon Cycle
1. Clearing Vegetation
2. Burning Fossil Fuels
potential consequences?
Gaseous Nitrogen (N2)in AtmosphereNitrogen
Fixationby industry
for agricultureFood Webson Land
Fertilizersuptake by
autotrophs
excretion, death,decomposition
uptake by
autotrophs
Nitrogenous Wastes,Remains in Soil
NO3–
in Soil
NO2–
in Soilloss byleaching
1. Nitrificationbacteria convert NH4
+
to nitrite (NO2–)
2. Nitrificationbacteria convert NO2
–
to nitrate (NO3–)
Ammonificationbacteria, fungi convert the
residues to NH3; thisdissolves to form NH4
+
NH3, NH4+
in Soil
loss byleaching
Nitrogen Fixationbacteria convert N2 toammonia (NH3); thisdissolves to formammonium (NH4
+)
Denitrificationby bacteria
The Nitrogen Cycle
Human Interferences in the Global Nitrogen Cycle
1.Add nitric oxide (NO) to atmosphere - can form acid rain
2.Add nitrous oxide N2O to atmosphere via anaerobic decomposition & inorganic fertilizers - greenhouse gas
3.Nitrate in inorganic fertilizers can leach thru soil & contaminate groundwater
4.Release large quantities of N into troposphere via habitat destruction
5.Upset aquatic ecosystems from excess nitrates in ag. runoff & sewage- eutrophication
Marine Sediments Rocks
Marine Food Webs
Dissolvedin OceanWater
Dissolvedin Soil Water,Lakes, Rivers
LandFoodWebs
Guano
Fertilizer
excretion
uptake byautotrophs
death,decomposition
sedimentation settling outuplifting overgeologic time
weathering
uptake byautotrophs
weathering
mining
leaching, runoff
agriculture
The Phosphorus Cycle
Human Interventions in the Phosphorus Cycle
1. Mining of phosphate rock
2. Clearing tropical forests reduces available phosphate in tropical soils
3. Phosphates from runoff of animal wastes, sewage & fertilizers disrupts aquatic ecosystems - eutrophication
“Since 1900, human activities have increased the natural rate of phosphorous release to environment by about 3.7 fold”
Ocean
Hydrogen sulfide
Industries
Volcano
Oxygen
Water AmmoniaSulfur trioxide Sulfuric acid Acidic fog and precipitation
Ammonium sulfate
Plants
Animals
Sulfate salts
Hydrogen sulfide
SulfurDecaying matterMetallicSulfidedeposits
Dimethyl sulfide
Sulfur dioxide
The Sulfur Cycle
How Do Ecologists Learn about Ecosystems?
Field research
Remote sensing
Geographic information system (GIS)
Laboratory research
Systems analysis
