Upload
shawn-hodge
View
216
Download
2
Tags:
Embed Size (px)
Citation preview
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