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Ecosystems: What Are They and How Do They Work?
Chapter 3
Dr. Wesam Al Madhoun
Core Case Study: Tropical Rain Forests Are Disappearing
Cover about 2% of the earth’s land surface
Contain about 50% of the world’s known plant and animal species
Disruption will have three major harmful effects• Reduce biodiversity• Accelerate global warming• Change regional weather patterns
Natural Capital Degradation: Satellite Image of the Loss of Tropical Rain Forest
3-1 What Is Ecology?
Concept 3-1 Ecology is the study of how
organisms interact with one another and with
their physical environment of matter and energy.
Cells Are the Basic Units of Life
Cell Theory: all living things composed of cells.
Eukaryotic cell: surrounded by membrane and has a distinct nucleus (a membrane bounded structure contain DNA)
Prokaryotic cell: surrounded by membrane but no distinct nucleus.
Structure of a Eukaryotic Call and a Prokaryotic Cell
Species Make Up the Encyclopedia of Life
Species: a set of individuals that can mate and introduce fertile offspring.
1.75 Million species identified
Insects make up most of the known species
Perhaps 10–14 million species not yet identified
Ecologists Study Connections in Nature
Ecology : study of how organism interact with their living environment of other organism and with their non living (a biotic) environment of soil, water and energy.
Levels of organization• Population: a group of individual of the same species living
in the same place, same time.• Genetic diversity: genetic variation in a population.
• Community: all the population of different species that live in a particular place.
• Ecosystem: a community of different species interacting with each other and with nonliving environment.
• Biosphere: consist of the parts of the earths, air water and soil where life is found.
Fig. 3-3, p. 52
Stepped Art
Smallest unit of a chemical element that exhibits its chemical propertiesAtom
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
Ecosystem A community of different species interacting with one another and with theirnonliving environment of matter and energy
Parts of the earth's air, water, and soil where life is found
Biosphere
Population of Glassfish in the Red Sea
Genetic Diversity in a Caribbean Snail Population
Science Focus: Have You Thanked the Insects Today?
Pollinators
Eat other insects
Loosen and renew soil
Reproduce rapidly
Very resistant to extinction
Importance of Insects
3-2 What Keeps Us and Other Organisms Alive?
Concept 3-2 Life is sustained by the flow of
energy from the sun through the biosphere, the
cycling of nutrients within the biosphere, and
gravity.
The Earth’s Life-Support System Has Four Major Components
Atmosphere• Troposphere: 17 km above sea level at tropic, and 7
km at north and south poles “contain majority of the air that we breath”.
• Stratosphere: 17-50 km above earth surface.
Hydrosphere: consist of all the water on and near the earth surface.
Geosphere: consist of the earth’s intensely hot core, a thick mantle of rock, thin outer crust.
Biosphere: occupies atmosphere, hydrosphere and geosphere where life exist.
Fig. 3-6, p. 55
Rock
AtmosphereVegetationand animals
Lithosphere
Biosphere
Mantle
Crust
Soil
Biosphere(living organisms)
Geosphere(crust, mantle, core)
Mantle
Core
Hydrosphere(water)
Crust(soil and rock)
Atmosphere(air)
Life Exists on Land and in Water
Biomes : large regions (forest, desert, grasslands) with distinct climate and certain species.
Aquatic life zones• Freshwater life zones• Lakes and streams
• Marine life zones• Coral reefs• Estuaries• Deep ocean
Fig. 3-7, p. 55
Average annual precipitation
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.)
AppalachianMountains
Coastal mountainranges
Sierra Nevada
Great American
Desert
RockyMountains
GreatPlains
MississippiRiver Valley
Deciduous forestCoastal chaparraland scrub
Coniferous forest Desert Coniferous forest Prairie grassland
San Francisco
BaltimoreDenver
St. Louis
Major Biomes along the 39th Parallel
What Happens to Solar Energy Reaching the Earth?
UV, visible, and IR energy
Radiation • Absorbed by ozone• Absorbed by the earth• Reflected by the earth• Radiated by the atmosphere as heat
Natural greenhouse effect
Fig. 3-8, p. 56
Lower Stratosphere(ozone layer)
Solarradiation
UV radiation
Visiblelight Heat radiated
by the earth
Mostabsorbedby ozone
Absorbedby the earth
Greenhouseeffect
Reflected byatmosphere Radiated by
atmosphereas heat
Heat
Troposphere
3-3 What Are the Major Components of an Ecosystem?
Concept 3-3A Ecosystems contain living
(biotic) and nonliving (abiotic) components.
Concept 3-3B Autotrophs (self feeding,
Heterotrophs (other feeders), Detritovores (feed
on waste or dead bodies).
Ecosystems Have Living and Nonliving Components
Abiotic• Water• Air• Nutrients• Rocks• Heat• Solar energy
Biotic• Living and once living
Major Biotic and Abiotic Components of an Ecosystem
Fig. 3-9, p. 57
Decomposers
Precipitation Oxygen (O2)
Carbon dioxide (CO2)
Producer
Primaryconsumer(rabbit)
Secondaryconsumer(fox)
Producers
Water
Soluble mineralnutrients
Several Abiotic Factors Can Limit Population Growth
Limiting factor principle
• Too much or too little of any a biotic factor can
limit or prevent growth of a population, even if
all other factors are at or near the optimal
range of tolerance.
Range of Tolerance for a Population of Organisms
INSERT FIGURE 3-10 HERE
Producers and Consumers Are the Living Components of Ecosystems (1)
Producers, autotrophs• Photosynthesis: the way, energy enter most ecosystem• Chemosynthesis: producers (bacteria) convert inorganic
compound to more complex nutrient without sun light.
Consumers, heterotrophs• Primary (plant eaters such as rabbits)• Secondary (meat eater, birds , frogs)• Third and higher level (tigers ,wolves)
Decomposers
Producers and Consumers Are the Living Components of Ecosystems (2)
Detritivores : feed on waste and dead bodies such as some insects and earth worms.
Aerobic respiration: use of oxygen to convert glucose (C6H12O6) back into carbon dioxide and water
Anaerobic respiration, fermentation: some decomposers get the energy they need by breaking down glucose in the absence of oxygen.
Science Focus: Many of the World’s Most Important Species Are Invisible to Us
Microorganisms
• Bacteria
• Protozoa
• Fungi
3-4 What Happens to Energy in an Ecosystem?
Concept 3-4A Energy flows through
ecosystems in food chains and webs.
Concept 3-4B 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 Flows Through Ecosystems in Food Chains and Food Webs
Food chain: a sequence of organism, each of which serves as a source of food or energy for the next.
Food web: a complex network of interconnected food chains.
Fig. 3-13, p. 62
Heat Heat
Heat
Heat Heat
Heat
Heat
Solarenergy
Tertiaryconsumers
(top carnivores)
First TrophicLevel
Second TrophicLevel
Third TrophicLevel
Fourth TrophicLevel
Producers(plants)
Primaryconsumers(herbivores)
Secondaryconsumers(carnivores)
Decomposers and detritus feeders
Usable Energy Decreases with Each Link in a Food Chain or Web
Biomass: the dry weight of all organic matter contained in its organisms.
Ecological efficiency: the % of useable chemical energy transferred as biomass from one trophic level to the next
Pyramid of energy flow: cumulative energy loss.
Fig. 3-15, p. 63
10
Heat
Heat
Heat
Heat
HeatDecomposers
Tertiaryconsumers(human)
Secondaryconsumers(perch)
Primaryconsumers(zooplankton)
Producers(phytoplankton)
Usable energy availableat each trophic level
(in kilocalories)
1,000
10,000
100
Some Ecosystems Produce Plant Matter Faster Than Others Do
Gross primary productivity (GPP): is the rate at which ecosystem producers (plants) convert solar energy into chemical energy as biomass found in their tissues.
Net primary productivity (NPP): NPP = GPP – R. where R is energy used in
respiration.
• Ecosystems and life zones differ in their NPP
Fig. 3-16, p. 64
Swamps and marshes
Terrestrial Ecosystems
Open oceanContinental shelf
Lakes and streamsEstuaries
Aquatic EcosystemsExtreme desert
Desert scrub
Tundra (arctic and alpine)
Temperate grasslandWoodland and shrubland
Agricultural landSavanna
Northern coniferous forest
Temperate forestTropical rain forest
4,000
Average net primary productivity (kcal/m2/yr)
9,6008,800800 1,600 2,400 8,0007,2003,200 6,4005,6004,800
3-5 What Happens to Matter in an Ecosystem?
Concept 3-5 Matter, in the form of nutrients,
cycles within and among ecosystems and the
biosphere, and human activities are altering
these chemical cycles.
Nutrients Cycle in the Biosphere
Biogeochemical cycles, nutrient cycles• Hydrologic• Carbon• Nitrogen• Phosphorus• Sulfur
Connect past, present , and future forms of life
Fig. 3-17, p. 66
Transpirationfrom plants
Evaporationfrom land
Precipitationto land
Precipitationto ocean
Evaporationfrom ocean
Condensation Condensation
Infiltrationand percolationinto aquifer
Surfacerunoff
Surface runoffRunoff
Globalwarming
Reduced recharge ofaquifers and floodingfrom covering land withcrops and buildings
Aquiferdepletion fromoverpumping
Increasedfloodingfrom wetlanddestruction
Pointsourcepollution
Groundwatermovement (slow)
Lakes andreservoirs
Ice andsnow
Ocean
Processes
Processes affected by humans
Reservoir
Pathway affected by humans
Natural pathway
Science Focus: Water’s Unique Properties
Properties of water due to hydrogen bonds between water molecules:• Exists as a liquid over a large range of
temperature• Changes temperature slowly• High boiling point: 100˚C• Expands as it freezes • Filters out harmful UV
Carbon Cycle Depends on Photosynthesis and Respiration
Link between photosynthesis in producers and respiration in producers, consumers, and decomposers
Additional CO2 added to the atmosphere
• Tree clearing• Burning of fossil fuels
Fig. 3-18, p. 68
Pathway affected by humans
Diffusion
Transportation
Deforestation
Respiration
Respiration
Decomposition
Forest fires
Compaction
Burningfossil fuels
Photosynthesis
Animals(consumers)
Plants(producers)
Marine food websProducers, consumers,decomposers
Carbonin plants
(producers)
Carbonin fossil fuels
Carbon dioxidedissolved in ocean
Carbonin limestone ordolomite sediments
Carbonin animals
(consumers)
Processes
Reservoir
Natural pathway
Carbon dioxidein atmosphere
Nitrogen Cycles through the Biosphere: Bacteria in Action (1)
Nitrogen fixed – N 2 converted to nutrient by:
• Lightning : electrical discharge in the atmosphere.• Nitrogen-fixing bacteria: in soil or plan roots.
Nitrification :is the biological oxidation of ammonia with oxygen into nitrite followed by the oxidation of these nitrites into nitrates
Denitrification: is a microbially facilitated process of nitrate reduction that may ultimately produce molecular nitrogen (N2) through a series of intermediate gaseous nitrogen oxide products.
Nitrogen Cycles through the Biosphere: Bacteria in Action (2)
Human intervention in the nitrogen cycle• Additional NO and N2O
• Destruction of forest, grasslands, and wetlands• Add excess nitrates to bodies of water• Remove nitrogen from topsoil
Fig. 3-19, p. 69
Decomposition
Nitrogenloss to deepocean sediments
Processes
Reservoir
Pathway affected by humans
Natural pathway
Nitrogenin atmosphere
Nitrogenin oceansediments Ammonia
in soil
Nitratein soil
Nitrogenin plants
(producers)
Nitrogenin animals
(consumers)Volcanicactivity
ElectricalstormsNitrogen oxides
from burning fueland using inorganicfertilizers
Nitratesfrom fertilizer
runoff anddecomposition
Nitrificationby bacteria
Denitrificationby bacteria
Uptake by plants
Bacteria
Fig. 3-20, p. 70
Projectedhumaninput
Total human input
Fertilizer andindustrial use
Nitrogen fixationin agroecosystemsFossil fuels
Year
2050200019801960194019201900
0
50
100
150
200
250
300
Nit
rog
en i
np
ut
(ter
agra
ms
per
yea
r)
3-6 How Do Scientists Study Ecosystems?
Concept 3-6 Scientists use field research,
laboratory research, and mathematical and other
models to learn about ecosystems.
Some Scientists Study Nature Directly
Field research: “muddy-boots biology”
New technologies available• Remote sensors• Geographic information system (GIS) software• Digital satellite imaging
2005, Global Earth Observation System of Systems (GEOSS) – integrate sensors, gauges and satellite that monitor earth, atmosphere and oceans
Some Scientists Study Ecosystems in the Laboratory
Simplified systems carried out in• Culture tubes and bottles• Aquaria tanks• Greenhouses• Indoor and outdoor chambers
Supported by field research
Some Scientists Use Models to Simulate Ecosystems
Computer simulations and projections
Field and laboratory research needed for baseline data