AP Biology
Ecosystems
Studying organisms in their environment
organism
population
community
ecosystem
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biosphere
Essential questions
 What limits the production in ecosystems?
 How do nutrients move in the ecosystem?
 How does energy move through the ecosystem?
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Ecosystem
 All the organisms in a community plus abiotic
factors

ecosystems are transformers of energy
& processors of matter
 Ecosystems are self-sustaining

what is needed?
 capture energy
 transfer energy
 cycle nutrients
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Ecosystem inputs
constant
energy flows
input
of
through
energy
nutrients cycle
Matter
cannot
Don’t forget
laws of or
bethe
created
Physics!
destroyed
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nutrients
can only
cycle
biosphere
inputs
 energy
 nutrients
Participants in an Ecosystem
 Primary producers-autotrophs that make
up the first trophic level of any ecosystem

Ex-plants, phytoplankton, & some bacteria
 Consumers-heterotrophs that feed on the
tissues, products, and remains of other
organisms

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Ex=herbivores, carnivores, omnivores,
parasites, detritivores, decomposers
Decomposers vs Detritivores
 Detritivores eat particles of decomposing
matter(detritus)
 Types Scavengers-animals that feed on
carrion, dead plant matter, or refuse.
Ex-buzzards, ants, & vultures
 Decomposers break down organic remains and
wastes off all organisms and return nutrients to
earth
 Ex-bacteria, protists, and fungi
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Energy flows through ecosystems
sun
secondary
consumers
(carnivores)
primary consumers
(herbivores)
producers (plants)
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loss of
energy
loss of
energy
sun
Inefficiency of energy transfer
 Loss of energy between levels of food
chain(only 10% is transferred b/t trophic levels)

To where is the energy lost? The cost of living!
17%
growth
only this energy
moves on to the
next level in
the food chain
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energy lost to
daily living
33%
cellular
respiration
50%
waste (feces)
Food chains
 Trophic levels
feeding relationships
 start with energy from
the sun
 captured by plants



1st
sun
top carnivore
Level 3
Secondary consumer
carnivore
Level 2
Primary consumer
heterotrophs
herbivore
level of all food chains
food chains usually go Level 1
Producer
up only 4 or 5 levels
 inefficiency of energy
transfer

Level 4
Tertiary consumer
all levels connect to
decomposers
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autotrophs
Decomposers
Bacteria
Fungi
Food webs
 Food chains are

linked together into
food webs
Who eats whom?

a species may
weave into web at
more than one level
 bears
 humans
 eating meat?
 eating plants?
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Types of Food Webs
 Grazing food web-energy flows mostly
into herbivores, carnivores, then
decomposers
 Detrital food web-energy from producers
flows mainly into detritivores and
decomposers.
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Biological Magnification in Food Webs
 In biological magnification, some chemical substance is passed
from organisms at one trophic level to those above and
becomes increasingly concentrated in body tissues.
 By 1995, people in the US were spreading more than 1.25
billion pounds of toxins per year! (insecticides, herbicides,
fungicides…)
 Example- The peregrine falcon almost became
extinct as a result of biomagnification of DDT (a
pesticide). DDT has been banned since the 70’s.
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sun
Ecological pyramid
 Loss of energy between levels of food
chain
1
100
100,000
1,000,000,000
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 Types of ecological pyramids
 Biomass pyramid-depicts the dry weight of all
of an ecosystem’s organisms at each tier
 Energy pyramid-illustrates how the amount of
usable energy diminishes as it is transferred
through an ecosystem
 Pyramid of numbers-shows how population
size decreases as you go from producer to
consumer
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Generalized
Nutrient
cycling
consumers
producers
consumers
decomposers
nutrients
nutrients
ENTER FOOD
CHAIN
made
available
= made available
to producers
to producers
Decomposition
connects all
trophic levels
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return to
abiotic
reservoir
abiotic
reservoir
geologic
processes
 In a biogeochemical cycle , an
essential element moves from the
environment, through ecosystems, then
back to the environment.
 Ex: O2,H,C,N, & P
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Carbon cycle
CO2 in
atmosphere
Diffusion
Respiration
abiotic reservoir:
 CO2 in atmosphere
enter food chain:
Combustion
of fuels =
 photosynthesis
carbon fixation in
Industry and home
Calvin cycle
Photosynthesis recycle:

return to abiotic:
 respiration
Plants
 combustion
Animals
Dissolved CO2
Bicarbonates
Photosynthesis
Animals
Plants and algae
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Carbonates in sediment
Deposition of
dead material
Deposition
of dead
material
Fossil fuels
(oil, gas, coal)
Nitrogen cycle
Carnivores
abiotic reservoir:
 N in atmosphere
enter food chain:
 nitrogen fixation by
soil & aquatic bacteria
recycle:
Herbivores
 decomposing &
nitrifying bacteria
return to abiotic:
 denitrifying bacteria
Birds
Plankton with
nitrogen-fixing
bacteria
Atmospheric
nitrogen
Plants
Death, excretion, feces
Fish
excretion
Decomposing bacteria
amino acids
Ammonifying bacteria
loss to deep sediments
Nitrogen-fixing
bacteria
(plant roots)
Nitrogen-fixing
bacteria
(soil)
Nitrifying bacteria
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soil nitrates
Denitrifying
bacteria
 Nitrogen fixation-bacteria convert
gaseous nitrogen to ammonia
 Denitrification-conversion of nitrate or
nitrite to gaseous nitrogen or nitrogen
oxide by certain bacteria in the soil
 Human activities add nitrogen to
ecosystems. Use of fertilizer and fossil
fuel burning are examples
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Phosphorus cycle
Plants
Land
animals
Soluble soil
phosphate
Loss in
drainage
fungi)
Rocks and
minerals
Decomposers Phosphates
(bacteria & fungi) in solution
Animal tissue
and feces
abiotic reservoir:
 rocks, minerals, soil
enter food chain:
 erosion releases
soluble phosphate
 uptake by plants
recycle:
 decomposing bacteria
Animal
tissue
&
fungi
Urine and feces
return to abiotic:
 loss toDecomposers
ocean
(bacteria and
sediment
Aquatic
animals
Plants and
algae
Precipitates
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Loss to deep sediment
abiotic reservoir:
 surface & atmospheric
water
enter food chain:
 precipitation & plant
uptake
Solar energy
recycle:
 transpiration
return to abiotic:
Evaporation
 evaporation & runoff
Water cycle
Transpiration
Water vapor
Precipitation
Oceans
Runoff
Lakes
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Percolation in soil
Groundwater
Aquifer
Transpiration
Remember
transpiration?
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Breaking the water cycle
 Deforestation breaks the water cycle

groundwater is not transpired to the
atmosphere, so precipitation is not
created
forest  desert
desertification
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QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Repairing the damage
 The Greenbelt Movement




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planting trees in Kenya
restoring a sustainable ecosystem
establishing democracy
empowering women
Wangari Maathai
Nobel Peace prize 2004
Studying ecosystems
Hubbard Brook
Experimental Forest
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7800 acres
38 acre deforestation
Effects of deforestation
40% increase in runoff

loss of water
 60x loss in nitrogen
 10x loss in calcium
loss into
surface water
Concentration
of nitrate (mg/l )
80 nitrate levels in runoff
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40
loss out of
ecosystem!
4
Deforestation
2
Why is
0
nitrogen
1965 so
important?
1966
1967
Year
1968
A Global Water Crisis
 Most water on Earth is too salty to drink (around 75%)
 2/3 of fresh water is used to irrigate fields
 About ½ of the US population taps into groundwater for
drinking water that can be contaminated.
 If the US population and water depletion continues, our
freshwater supply will be in danger.
 Important terms:


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Salinization-a build up of salt in soil that stunts crop plants
and decreases yields.
Desalination-removal of salt from sea water
Greenhouse Gases, Global Warming
 The greenhouse effect occurs when greenhouse gases trap
heat in the lower atmosphere.
 This makes Earth’s surface warm enough to support life.
 Natural processes and human activities are adding more
greenhouse gases to the atmosphere.
 Examples: carbon dioxide, CFCs, methane, & nitrous
oxide
 This results in a result in global warming and climate change.
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