Ecosystems

Chapters 55 & 56

Ecosystems

All abiotic factors & species

ecosystems

◀ An island ecosystem

▼ A desert springecosystem

Ecosystems

Processes in the ecosystems1. Energy

Comes from sunPhotosynthesis(chemical energy)

2. Biogeochemical cycles(nutrients)Chemicals that move through

ecosystems Mostly found in nonliving reservoirs

Sun

Lossof

heat

Key

Chemical cycling

Energy flow

Primary producers

Primaryconsumers

Detritus

Secondary and Microorganismsand other

detritivorestertiaryconsumers

Ecosystems

Photosynthesis Decomposition & respiration

return elements to abiotic forms Elements are recycledEnergy is released as heatSun continuously supplies energyEvaporation & precipitation

circulate elements

Trophic levels

Energy flow through the ecosystemAutotrophs: primary producersHeterotrophs: consumersPrimary consumers: herbivores Secondary consumers: carnivoresDecomposers: break down organic

matterDetritivore: live on refuse of

ecosystem

Trophic levels

“trophos” means feederAll levels feed on anotherFood chain Represents these levelsFood web:More complex relationships

between levels

Decomposers

▼ Fungi decomposinga dead tree

▲ Rod-shaped and sphericalbacteria in compost (colorizedSEM)

Food chain

Food chain

Food web

Energy flow

Primary productivity:Amount of energy produced by

photosynthesis (organic matter) in a community

Biomass:Total mass of organisms in an

ecosystemRainforests or wet lands have a high

productivity

Energy flow

Secondary productivityRate of biomass of heterotrophsLess than primary due to1. Not all plants are consumed

by herbivores2. Some energy of herbivores is

passed as waste3. Some energy is lost as heat

Energy flow

Energy flow

Gross primary production (GPP)

Amount light energy converted to chemical energy over time

Net primary production (NPP)GPP less the amount of energy for

plant cellular respiration (R)NPP= GPP-R

Energy flow

Net primary production (kg carbon/m2·yr)

0 1 2 3

·

Energy flow in food chains

Ecological pyramidsRelationship of energy, biomass

or numbers in an ecosystemThe limit is based on amount of

sunlight and nutrients available

Ecological pyramids

Ecological pyramids

Ecological pyramids

Ecological pyramids

Water cycle

Oceans cover ¾ of earth’s surfaceSun powers evaporation of water from

oceans90% of water in atmosphere over

land comes from plant transpirationMost falls over the ocean as rain2% is frozen in iceWater supplies the hydrogen in ATP

formation

Water cycle

Carbon cycle

Photosynthesis uses up about 10% of atmospheric CO2

Respiration replaces CO2 in the air

Most CO2 is in fossil fuels, coals, gas

Use of these is increasing CO2 in the atmosphere

Carbon cycle

Nitrogen cycle

Prokayotes “fix” nitrogen to usable form

Nitrogen is being added to the system by fertilizers

Nitrogen cycle

Phosphorus cycle

Exist in mineral form (not atmosphere)

Need for ATP, phospholipids, DNA, RNA

Fertilizers adding a lot

Phosphorus cycle

Ecosystem stabilization

More diverse species (species richness)

1. Ecosystem productivity2. Spatial heterogencity

More habitat variation (soils, topography) allows more areas for animals to live

3. Climate More stable the weather the greater the

species

Biodiversity hotspots

Biodiversity

Biodiversity

1. Genetic diversity2. Species diversity3. Ecosystem diversity

Threats to Biodiversity

Habitat lossIntroduced speciesOverexploitation

Problems

PollutionRhine river (Mercury, pesticides

1986)DDT (chlorinated hydrocarbons)Absorbed in animal fatsBiological magnification:Become more concentrated in

food chain

DDT

Acid rain

Sulfur dioxideForms sulfuric acid when comes

with rainLowers pHKills wildlife

Acid rain

Farming

Ozone layer

Protects against UVThinning 1975Chloroflurocarbons (CFC’s)Increased melanoma

Ozone

Ozone

Greenhouse effect

Increased carbon dioxide & other gases

Reflects heat from earthKeeping it in the atmosphereGlobal warming

Greenhouse effect

Effect of warming

Plants/animals further northMigratory changesSpecies have problems adaptingIncreasing sea levelRetreating glaciersMore severe weather changes

Logging

Conservation

Conservation Biology:Attempts to conserve

biodiversityRestoration Ecology:Return ecosystems to natural

state