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Ecosystems
An ecosystem is all of the organisms in an area,
along with their nonliving environment
Example: aquarium
Living + Non-living
(Biotic + Abiotic)
Trophic Levels
Organisms in a
community are related
to each other through
feeding relationships
Each step up in the
transfer of energy is
known as a trophic level
All energy ultimately
comes from the SUN
Trophic Levels
Decomposers/
Detritivores
Eat detritus (organic
waste/remains of dead
organisms)
Can fit in to a food
chain or web at any
location
Trophic
Levels
Producers
Convert solar (or
chemical) energy into
organic compounds
Primary consumers
Eat producers
Secondary consumers
Eat primary consumers
Tertiary consumers
Eat secondary consumers
Pyramid of
Numbers/Biomass/Ener
gy
Numbers, energy,
& biomass
decreases as one
moves up the
food chain.
Biomass- dry
mass of organic
matter
Trophic Levels
Ten-Percent Law
Usable energy is lost through each transfer of energy
Why? (Remember the law of conservation of energy says energy
cannot be created or destroyed; it only changes form.)
Only about 10% of the energy at one trophic level is transferred
to the next trophic level. 90% is lost as heat with each transfer.
Food Chain
A straight-line
marsh hawk
upland sandpiper
sequence of who
eats whom
garter snake
Simple food
chains are rare in
nature
cutworm
plants
Tall-Grass Prairie Food Web
marsh hawk
sandpiper
crow
snake
frog
weasel
badger
coyote
spider
sparrow
earthworms, insects
vole
pocket
gopher
grasses, composites
ground
squirrel
Primary Productivity
Primary Productivity:
The amount of light energy converted to sugars by
autotrophs in an ecosystem
Gross vs. Net Primary Productivity
GPP: the amount of light energy that is converted to
chemical energy by photosynthesis per unit time
NPP: GPP minus the energy used by the primary
producers for cellular respiration
GPP-R=NPP
Limiting Nutrients
What limits primary production?
Aquatic Ecosystems
Light (depth penetration)
Nitrogen
Phosphorus
Terrestrial Ecosystems
Temperature
Moisture
Minerals (N & P are the main limiting factors for plants.)
Biogeochemical Cycle
The flow of a nutrient from the environment to living
organisms and back to the environment
Main reservoir for the nutrient is in the environment
Hydrologic Cycle
Atmosphere
wind-driven water vapor
40,000
evaporation precipitation
from ocean into ocean
425,000
385,000
precipitation
onto land
111,000
evaporation from land
plants (evapotranspiration)
71,000
surface and
groundwater
flow 40,000
Ocean
Land
Figure 48.14
Page 876
diffusion between
atmosphere and ocean
bicarbonate and
carbonate in
ocean water
photosynthesis
combustion of fossil fuels
aerobic
respiration
marine food
webs
death,
incorporation sedimentation
into sediments
uplifting
sedimentation
marine sediments
Carbon Cycle - Marine
Figure 48.16
Page 878
atmosphere
combustion of
fossil fuels
volcanic action
terrestrial
rocks
weathering
photosynthesis
aerobic combustion
respiration of wood
sedimentation
land food
webs
soil water
leaching,
runoff
death, burial,
compaction over
geologic time
Carbon Cycle - Land
peat,
fossil
fuels
Figure 48.16
Page 878
Carbon in Atmosphere
Atmospheric carbon is mainly carbon
dioxide
Carbon dioxide is added to atmosphere
Aerobic respiration, volcanic action,
burning fossil fuels
Removed by photosynthesis
Greenhouse Effect
Greenhouse gases impede the escape of heat from
Earth’s surface
Figure 48.18, Page 880
Global Warming
Long-term increase in the temperature of Earth’s
lower atmosphere
Figure 48.19, Page 881
Nitrogen Cycle
Nitrogen is used in amino acids and nucleic acids
Main reservoir is nitrogen gas in the atmosphere
Nitrogen Cycle
gaseous nitrogen (N2)
in atmosphere
nitrogen fixation
by industry
food webs
on land
uptake by excretion, death, uptake by
fertilizers autotrophs decomposition autotrophs
nitrogen
fixation
NH3-,NH4+
in soil
leaching
nitrogenous
wastes, remains
NO3in soil
dentrification
ammonification 2. Nitrification
1. Nitrification
NO2in soil
leaching
Figure 48.21
Page 882
Nitrogen Fixation
Plants cannot use nitrogen gas
Nitrogen-fixing bacteria convert
nitrogen gas into ammonia (NH3)
Ammonia and ammonium can be
taken up by plants
Ammonification &
Nitrification
Bacteria and fungi carry out ammonification
conversion of nitrogenous wastes to ammonia
Nitrifying bacteria convert ammonium to nitrites
and nitrates
Nitrogen Loss
Nitrogen is often a limiting factor in ecosystems
Nitrogen is lost from soils via leaching and
runoff
Denitrifying bacteria convert nitrates and
nitrites to nitrogen gas
Phosphorus Cycle
Phosphorus is part of phospholipids and all
nucleotides
It is the most prevalent limiting factor in ecosystems
Main reservoir is Earth’s crust; no gaseous phase
Phosphorus Cycle
mining
FERTILIZER
GUANO
excretion
agriculture
uptake
by
autotrophs
MARINE
FOOD
WEBS
weathering
DISSOLVED
IN OCEAN
WATER
uptake
by
autotrophs
weathering
DISSOLVED IN
SOILWATER,
LAKES, RIVERS
death,
decomposition
sedimentation
LAND
FOOD
WEBS
death,
decomposition
settling
out
leaching, runoff
uplifting
MARINE SEDIMENTS
TERRESTRIAL ROCKS
over geologic time
Figure 48.23, Page 884
Human Impact on
Ecosystems
Increased Eutrophication of
Lakes
Increase in nutrient levels
(phosphates, nitrates, etc.)
Can lead to algal blooms
Hypoxia
What is it?
Why?
Can lead to the eventual loss of
fish and other aquatic organisms
Accelerated by sewage/factory
wastes, leaching of fertilizers into
freshwater
Human Impact on
Ecosystems
Combustion of Fossil
Fuels
Leads to acid
precipitation
Changes the pH of
aquatic ecosystems
and affects the soil
chemistry of terrestrial
ecosystems
Human Impact on
Ecosystems
Biological Magnification
Toxins become more
concentrated as they move up
the food chain
Toxins that are lipophilic cannot
be excreted in urine (water!), so
they are stored in fatty tissue
(adipose tissue) unless the
organism has enzymes to break
it down
Important examples?
The biomass at any given
trophic level is produced from
a much larger biomass
ingested from the level below
Human Impact on
Ecosystems
Increasing Carbon Dioxide Concentration in the
Atmosphere
Burning fossil fuels (wood, coal, oil) releases CO2
Carbon dioxide and water in the atmosphere retain
solar heat, causing the greenhouse effect
Human Impact on
Ecosystems
Use of chlorofluorocarbons has destroyed ozone
(O3) by converting it to oxygen gas.
Ozone protects against UV radiation
Increasing skin cancers, cataracts
What are your odds of getting skin cancer in your
lifetime?
Rain Shadow
Air rises on the windward side, loses moisture
before passing over the mountain Leeward
side is in the rainshadow; deserts
Figure 49.7
Page 893
Biomes
Regions of land characterized by habitat
conditions and community structure
Distinctive biomes prevail at certain latitudes
and elevations
Tropical Forests
May be dry, deciduous, or rainforests
T. Rainforest
Abundant rainfall
4 layers to forest (upper & lower canopy, shrub
understory, & herbaceous layer)
Poor soil due to leaching
Highest species diversity
Grasslands
Savannas
Tropical & subtropical with scattered trees
3 seasons: cool & dry; hot & dry; warm wet.
Frequent fires
Grazing mammals
(African grasslands)
Chaparral
Along coastlines in mid latitudes
Mild, rainy winters & hot, dry summers
Evergreen shrubs
Periodic fires
Browsers, rodents reptiles
Temperate Grassland (Prairie)
Similar to savannah without trees
Cold winters
Maintained by fire
Seasonal drought
Rich soils
Grazing animals; herbivores
Temperate Deciduous
Forest
Our biome
3 layered forest
Dominant species are deciduous trees
Midlatitudes
Deserts
Less than 10 centimeters annual rainfall, high
level of evaporation
Tend to occur at 30 degrees north and south
and in rain shadows
One-third of land surface is arid or semiarid
Arctic
Tundra
Occurs at high
latitudes
Permafrost lies
beneath surface
Nutrient cycling is very
slow
Do not post
on Internet
Coldest biome
Arctic tundra in Russia in summer
Low species diversity
Figure 49.19
Page 903
Taiga (coniferous forest)
Found in northern latitudes
Harsh winters; short summers
Thin, acidic soil
Coniferous trees
No permafrost
Alpine Tundra
Occurs at high
elevations
No underlying
permafrost
Plants are low cushions
or mats as in Arctic
tundra
Do not post
on Internet
Figure 49.19
Page 903
Lakes
Bodies of standing freshwater Eutrophic:
shallow, nutrient-rich, has high primary
productivity, Oligotrophic: deep, nutrientpoor, has low primary productivity
Lake Zonation
LITTORAL
LITTORAL
LIMNETIC
PROFUNDAL
Figure 49.21
Page 904
Thermal Layering
In temperate-zone lakes, water can form distinct
layers during summer
THERMOCLINE
Figure 49.22
Page 904
Seasonal Overturn
In spring and fall, temperatures in the lake
become more uniform
Oxygen-rich surface waters mix with deeper
oxygen-poor layers
Nutrients that accumulated at bottom are
brought to the surface
Ocean Provinces
neritic
zone
oceanic
zone
intertidal
zone
continental
shelf
BENTHIC
PROVINCE
bathyal
shelf
PELAGIC
PROVINCE
0
200
1,000
abyssal
zone
2,000
4,000
hadal zone
Figure 49.24
Page 906
deep-sea
trenches
11,0000
depth (meters)
Phytoplankton
Floating or weakly swimming photoautotrophs;
form the base for most oceanic food webs
Ultraplankton are photosynthetic bacteria
Hydrothermal Vents
Openings in ocean floor that
spew mineral-rich,
superheated water
Do not post
on Internet
Primary producers are
chemoautotrophic bacteria;
use sulfides as energy
source
Tube worms at hydrothermal vent
Figure 49.26
Page 907
Estuary
Partially enclosed area where saltwater and
freshwater mix
Dominated by salt-tolerant plants
Examples are Chesapeake Bay, San
Francisco Bay, salt marshes of New England
Estuarine Food Webs
Primary producers are phytoplankton and salttolerant plants
Much primary production enters detrital food
webs
Detritus feeds bacteria, nematodes, snails,
crabs, fish
Intertidal Zones
Littoral zone is submerged only during highest
tides of the year
Midlittoral zone is regularly submerged and
exposed
Lower littoral is exposed only during lowest
tides of the year
Rocky
Intertidal
Grazing food webs prevail
Vertical zonation is readily
apparent
Diversity is greatest in
lower littoral zone
Figure 49.29
Page 909
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on Internet
Upwelling
Upward movement of
water along a coast;
replaces surface
waters that move away
from shore
Figure 49.31
Page 910