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