Download ecosystems - Falmouth Schools

Ecosystems
Chapter 54
• Ecosystem involves all abiotic and
biotic factors in area.
• Trophic levels - groups in which
organisms are placed according to
eating patterns.
• Ecosystems - involve nutrient
cycles.
http://www.oahunaturetours.com/pelagic/images/sbbfoodchain1.GIF
• Autotrophs - self-feeders (usually
photosynthesize) -primary
producers
• They use light to make sugars,
other chemicals necessary for life.
http://static.howstuffworks.com/gif/irrigation-photosynthesis.gif
• Heterotrophs - rely on organisms
for food.
• Herbivores – eat primary producers
(primary consumers)
• Carnivores - eat primary consumers
(secondary consumers)
• Tertiary consumers - eat secondary
consumers.
• Detritivores - decomposers - break
down detritus (dead organic matter
left after organism dies)
• Organic matter must be recycled in
ecosystem.
• Biggest decomposers - fungi and
prokaryotes (secrete enzymes to
break down dead material)
• Primary production - amount of
light that can be converted to
energy in a given time.
• All contributes to energy budget in
an area (determines how much
energy available to ecosystem)
http://adaptation.nrcan.gc.ca/posters/images/pr_02_01_e.gif
• Gross primary productivity amount of light energy converted to
chemical energy.
• Net primary productivity - gross
productivity minus amount of
energy used by primary producers
for respiration (amount of energy
left over)
http://eostc.umt.edu/forestry/Products/Production/Forest%20Production/first_modis_gpp.g
• Primary production - expressed in
terms of biomass (amount of
vegetation added to ecosystem per
unit area per unit time)
• Each ecosystem different amount
of biomass.
• Oceans - amount of light to hit
ocean floor contributes biomass.
• Light can only go to certain level;
primary productivity of area may be
lower in deeper oceans.
Primary Productivity Map
• Nutrients also contribute to
biomass in aquatic areas.
• Nitrogen - plant growth (can be
limited in water)
• Water pollution adds nutrients to
water (eutrophication)
• Shifts organisms living in water and
is a negative impact of humans.
Eutrophication of lake
• Land areas - temperature and water
availability also determines primary
productivity.
• Minerals in soil can affect
production as well.
http://www.usf.uni-osnabrueck.de/~hlieth/npp/npp.gif
• Efficiency between trophic levels is
at best 20%.
• Transfer from one level to next is
only 20% of energy from level
before.
• Biomass pyramids show
transformations between trophic
levels.
• Differ dramatically between
ecosystems.
• Nutrient cycling involves abiotic
and biotic factors (biogeochemical
cycling)
• Water cycling physical cycle and
not chemical; not considered
biogeochemical cycle, but still
essential to ecosystem.
Carbon cycle is a biogeochemical cycle.
• Nitrogen enters an ecosystem in 2
ways.
• Added to soil in usable form.
• Can also enter through nitrogen
fixation - prokaryotes convert
nitrogen into usable organic
compounds like amino acids.
• Product of nitrogen fixation is
ammonia.
• Ammonia picks up H+ in soil to
become ammonium (ammonification)
• Plants can use this nitrogen.
• Aerobic bacteria can turn
ammonium into a nitrate
(nitrification)
http://www.thisland.uiuc.edu/50ways/images/5b.jpg
• Nitrates - used by plants.
• In final step, other bacteria use
oxygen from nitrates and release
N2 back into atmosphere
(denitrification)
http://generalhorticulture.tamu.edu/lectsupl/Nutrient/p79f1.gif
• Phosphorus occurs only in
phosphate - plants absorb and use
to make organic nutrients.
• Does not come from atmosphere.
• Recycling of phosphorus is usually
confined to specific areas.
• Rate of decomposition determines
rate of chemical cycling.
• Tundra - decomposition can take
years; rain forest - decomposition
takes much less time.
http://farm1.static.flickr.com/221/507417180_dfd8f5e8ac.jpg?v=0
• Humans affect rate of chemical
cycling due to habits.
• Farmers - disturb crop areas by
removing nutrients in soil.
• Humans - add fertilizers to soil
which disrupt chemical balances.
• Chemicals can enter water,
disrupting animals that live there.
• Burning of fossil fuels - major
contributors to nutrients in
atmosphere.
• Sulfur and nitrogen placed into
atmosphere change into acid
precipitation.
Acid precipitation
• Acid precipitation can alter pH of
soil and alter the vegetation that
lives there.
• Poisonous materials also added to
our soils and water.
• Further up food chain, more
organism is affected by chemicals.
• DDT (a pesticide) damaged birds
and fish when it met with water.
• Amount of carbon dioxide in
atmosphere has been rising for
decades.
• Carbon dioxide helps to keep in
heat that would normally escape
atmosphere (greenhouse effect)
• Ozone layer is thinning as a result
of fossil fuels.
• Ozone protects humans from UV
rays.