Introduction to Ecology Chapters 52. Figure 50.3 Rachel Carson
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- Introduction to Ecology Chapters 52
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- Figure 50.3 Rachel Carson
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- Ecology Ecology the study of interactions between organisms and
the environment Biotic living components of an ecosystem (ex.
animals and plants) Abiotic - nonliving components of an ecosystem
(ex. soil, air, and water)
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- Species distribution Interactions between organisms and the
environment limit the distribution of species. What affects the
distribution of species? Dispersal limits (range expansions and
species transplants) Behavior and habitat selections Biotic factors
(other species) Abiotic factors (temperature, water, sunlight,
wind, rocks/soil, and climate)
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- Figure 50.7 Spread of the African honeybee in the Americas
since 1956
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- Figure 50.11 Solar radiation and latitude
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- Figure 50.12 What causes the seasons?
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- Figure 50.14 How mountains affect rainfall
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- Figure 50.18 Zonation in a lake
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- Figure 50.22 Zonation in the marine environment
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- Figure 50.24 The distribution of major terrestrial biomes
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- Figure 50.10 A climograph for some major kinds of ecosystems
(biomes) in North America
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- POPULATION ECOLOGY CHAPTER 53
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- POPULATION CHARACTERISTICS Population organisms of the same
species in the same area Density number of individuals in a given
area (example: 1200/m 2 ) Dispersion pattern of spacing among
individuals
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- Measuring Size Quadrant method used for stationary organisms
Mark and recapture used for mobile organisms
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- Patterns of Dispersion Clumped individuals aggregated in
patches (most common) Uniform evenly spaced individuals Random
unpredictable, patternless
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- Patterns of dispersion within a populations geographic
range
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- DEMOGRAPHY Demography is the study of factors that affect
populations Age structure relative number of individuals of each
age Birthrate or fecundity number of offspring born during a
certain time period Death rate number of individuals who die in a
certain time period Generation time average span between birth of
individuals and the birth of their offspring Sex ratio proportion
of individuals of each sex
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- Life tables used to determine how long, on average, an
individual of a given age could be expected to live Cohort group of
individuals of same age Survivorship curve a plot of the numbers in
a cohort that are alive at each age
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- Life Table for Belding Ground Squirrels (Spermophilus beldini)
at Tioga Pass, in the Sierra Nevada Mountains of California
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- Idealized survivorship curves
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- LIFE HISTORIES Life history traits that affect an organisms
schedule of reproduction and death Life histories vary greatly
Salmon travel to ocean to mature and then back to stream to
reproduce Some oaks cannot reproduce until they are at least 20
years old Semelparity or big bang reproduction produce numerous
offspring and then die Iteroparity or repeated reproduction produce
fewer offspring over many seasons
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- An example of big-bang reproduction: Agave (century plant)
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- There is a trade-off between reproduction and survival Female
red deer who are reproductive have a greater chance of dying Larger
brood sizes increase mortality rate
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- Cost of reproduction in female red deer on the Island of Rhum,
in Scotland
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- Probability of survival over the following year for European
kestrels after raising a modified brood
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- POPULATION GROWTH N = Change in population size B = # births
during time interval (birth rate) D = # deaths during time interval
(death rate) t = time interval N/t = B D Per capita birthrate (b)=
# offspring produced per time by an average member of population
Ex. 46 births/year in pop of 1000 so b = 46/1000 = 0.046 Birth rate
= Expected # births/year for pop (B): B=bN Ex. B = 0.046 x 500 = 23
births/year (where N = 500)
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- Per capita death rate (m)= # deaths per time by an average
member of population Ex. 22 deaths/year in pop of 1000 so m =
22/1000 = 0.022 Death rate = Expected # deaths/year for pop (D):
D=mN Ex. D = 0.022 x 500 = 11 deaths/year (where N = 500) Maximum
per capita growth rate (r max ) N/t = bN mN (birthrate death rate)
r = b m N/t = r max N (exponential growth rate) dN/dt = r max N
(calculus version)
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- If a population is growing, r is positive. If a population is
declining, r is negative. Zero population growth occurs when r = 0
Exponential growth maximum population growth rate Intrinsic rate of
increase is the maximum population growth rate, r max Exponential
growth is: dN/dt = r max N
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- Population growth predicted by the exponential model
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- Example of exponential population growth in nature
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- Carrying capacity (K) maximum population size that a particular
environment can support with no net increase or decrease Logistic
Growth incorporates the effect of population density on r max,
allowing it to vary from r max under ideal conditions to zero as
carrying capacity is reached.
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- When N is small compared to K, the per capita rate of increase
is high. (N = pop size) When N is large and resources are limiting,
the per capita rate of increase is small. When N = K, pop stops
growing. For logistic growth: N/t = r max N (K-N/K)
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- Population growth predicted by the logistic model
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- How does the logistic curve fit real populations? Some
populations closely follow the S-shaped curve. Other populations do
not. Low numbers may hurt a population (rhinos) Populations may
overshoot the carrying capacity and then drop below K.
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- How well do these populations fit the logistic population
growth model?
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- Strategies K-selected populations (density dependent) organisms
that are likely to be living at density near the limit imposed by
the environment (K) r-selected populations (density indepedent)
organisms that are likely to be living in variable environments in
which populations fluctuate or in open habitats where individuals
are likely to face little competition
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- Characteristicsr-selectedK-selected Maturation timeShortLong
LifespanShortLong Death rateOften highUsually low
#offspring/episodeManyFew # reproductions/ lifetime Usually
oneOften several Timing 1 st reproductionEarly in lifeLate in life
Size of offspring/eggsSmallLarge Parental carenone Often
extensive
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- POPULATION LIMITING FACTORS Limiting factors factors that limit
population growth Density dependent factors death rate rises or
birth rate falls with increasing pop density Disease Predation
Competition Lack of food Lack of space Density independent birth
rate or death rate that does not change with pop density
Climate
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- Decreased survivorship at high population densities
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- Long-term study of the moose (Alces alces) population of Isle
Royale, Michigan
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- Extreme population fluctuations
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- Population cycles in the snowshoe hare and lynx
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- Human population growth
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- Demographic transition in Sweden and Mexico, 1750-1997
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- Age-structure pyramids for the human population of Kenya
(growing at 2.1% per year), the United States (growing at 0.6% per
year), and Italy (zero growth) for 1995
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- Annual percent increase in global human pop (data from 2005).
Sharp dip in 1960 due mainly to famine in China that killed 60
million people.
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- Infant mortality and life expectancy (from 2005)
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- COMMUNITY ECOLOGY CHAPTER 54
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- COMMUNITIES Communities different populations living within the
same area What factors are most significant in structuring a
community?
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- INTERACTIONS Interspecific interactions occur between different
populations within a community Coevolution a change in one species
acts as a selective force on another species, and
counter-adaptation by the second species, which may cause a
selective force on the 1 st species.
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- Predation (+/-) Lion hunting, killing, and eating a zebra
Parasitism (+/-) Ticks sucking blood of human Competition (-/-)
Fighting over resources Commensalism (+/0) Birds feeding on insects
which bison flush out of grass Mutualism (+/+) Legumes with
nitrogen fixing bacteria Herbivory (+/-) Insects eating plants
Disease (pathogens) (+/-) Bacteria, viruses, protists, fungi, and
prions
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- Figure 53.x2 Parasitic behavior: A female Nasonia vitripennis
laying a clutch of eggs into the pupa of a blowfly (Phormia
regina)
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- Figure 53.9 Mutualism between acacia trees and ants. The ants
live in the hollow thorns and sting other pests.
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- Predation Cryptic coloration camouflage Aposematic coloration
when animals with effective chemical defenses are brightly colored
as a warning
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- Figure 53.5 Camouflage: Poor-will (left), lizard (right)
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- Figure 53.6 Aposematic (warning) coloration in a poisonous blue
frog
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- Figure 53.x1 Deceptive coloration: moth with "eyeballs"
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- Mimicry an organisms mimic another Batesian mimicry a harmless
species mimics a harmful or unpalatable species Mullerian mimicry
two or more aposematically species resemble each other
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- Figure 53.7 Batesian mimicry: the hawkmoth larva resembles a
snake
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- Figure 53.8 Mllerian mimicry: Cuckoo bee (left), yellow jacket
(right)
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- Competition Competitive exclusion principle two species with
similar needs for the same limiting resources cannot coexist in the
same place. Could lead to extinction of one species Ecological
niche ecological role; the sum total of the organisms use of biotic
and abiotic resources
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- Resource partitioning sympatric (geographically overlapping)
species consume slightly different foods or use resources in
slightly different ways. Character displacement characteristics are
more divergent in sympatric populations compared to geographically
isolated (allopatric) populations
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- Figure 53.3a Resource partitioning in a group of lizards
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- Figure 53.2 Testing a competitive exclusion hypothesis in the
field
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- Figure 53.3bc Anolis distichus (left) perches on sunny areas
and Anolis insolitus (right) perches on shady branches.
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- What controls community structure? Species diversity Food webs
Dominant species Keystone species Foundation species
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- Figure 53.21 Which forest is more diverse?
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- Species Diversity Species diversity considers the following:
Species richness number of different species Species relative
abundance proportion each species represents of the total
individuals in community
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- Dominant species most abundant or highest biomass Ex. American
Chestnut was dominant before 1910, but chestnut blight killed all
in N. America Invasive species can become dominant Keystone species
a predator that makes an unusually strong impact on community
structure Keystone predators maintain higher species diversity by
reducing the densities of strong competitors, such that the
competitive exclusion of other species does not occur Ex. Removing
Piaster decreased species diversity. Without piaster, mussels
overpopulated and excluded other species,
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- Figure 53.14b Testing a keystone predator hypothesis
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- Figure 53.14a Testing a keystone predator hypothesis
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- Figure 53.15 Sea otters as keystone predators in the North
Pacific Without sea otters, sea urchins do well and eat kelp. Kelp
forests are being destroyed. Otters are being eaten by killer
whales.
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- Foundation species - cause physical changes to environment Ex.
beaver dam, black rush (grass) helps prevent salt build up in soil
of marshes
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- Bottom-up or Top-down Controls Bottom-up = influence from lower
to higher trophic levels Mineral nutrients control the plants,
which control the herbivores, which then controls the predators
Top-down = influence from higher to lower trophic levels Predators
limit herbivores, which in turn limits plants, which affects soil
nutrients
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- DISTURBANCES Disturbances are events such as fire, storms,
drought, or human activities that damage communities. Can create
opportunities for other species Human disturbance is not always
negative Yellowstone fire in 1988 killed old forest, but new plants
quickly grew in its wake Dynamic equilibrium hypothesis species
diversity depends on the effect of disturbance on the competitive
interactions of populations.
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- Figure 53.16 Routine disturbance in a grassland community
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- Figure 53.18x2 Forest fire
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- SUCCESSION Ecological succession transitions in species
composition over time Primary succession when succession begins in
an area that is virtually lifeless and has no soil. Lichens and
mosses are usually the first macroscopic photosynthesizers Can
slowly dissolve rock to make soil, which takes thousands of
years
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- Figure 53.18x1 Large-scale disturbance: Mount St. Helens
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- Figure 53.19 A glacial retreat in southeastern Alaska
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- Table 53.2 The Pattern of Succession on Moraines in Glacier
Bay
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- Secondary succession occurs where an existing community has
been cleared by some disturbance that leaves soil intact (example
fire or volcanoes erupting) Typically pioneer species are
r-selected (high birthrates and dispersal)
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- Figure 53.18 Patchiness and recovery following a large-scale
disturbance
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- ECOSYSTEMS Chapter 55
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- FOOD WEBS and TROPHIC LEVELS Autotrophs Producers make own food
Heterotrophs Primary consumers = herbivores = eat producers
Secondary consumers = carnivores = eat primary consumers Tertiary
consumers = carnivores = eat secondary consumers Detritivores
(decomposers) = eat detritus (nonliving organic material and dead
remains)
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- Figure 54.1 An overview of ecosystem dynamics
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- Section 3-2 A Food Web
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- Figure 54.2 Fungi decomposing a log
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- Production rate of incorporation of energy and materials into
the bodies of organisms Consumption metabolic use Decomposition
breakdown of organic material into inorganic
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- ENERGY FLOW IN ECOSYSTEMS Most solar radiation is absorbed,
reflected, or scattered in the atmosphere of Earth. Only a very
small portion of sunlight is used by algae, bacteria, and plants
for photosynthesis
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- Primary productivity amount of light energy converted to
chemical energy by autotrophs in an ecosystem in a given time
period Gross primary productivity (GPP) total primary productivity
(not all of this energy is stored in autotrophs because autotrophs
use energy for respiration) Net primary productivity (NPP) NPP =
GPP R Where R = the amount of energy used in respiration
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- C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O Gross primary productivity
results from photosynthesis Net primary productivity is the
difference between the yield of photosynthesis and the consumption
of fuel in respiration Respiration Photosynthesis
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- Primary productivity J/m 2 /yr (energy measured per area per
unit time) g/m 2 /yr (biomass added per area per unit time)
Seasonal changes and available nutrients can limit primary
productivity
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- Figure 54.3 Primary production of different ecosystems
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- Figure 54.4 Regional annual net primary production for
Earth
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- Limiting nutrient the nutrient that must be added to increase
primary productivity Example: nitrogen or phosphorus are often
limiting in aquatic systems (especially in the photic zone)
Secondary productivity rate at which an ecosystems consumers
convert chemical energy into their own new biomass
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- Figure 54.9 Nutrient addition experiments in a Hudson Bay salt
marsh
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- Figure 54.11 An idealized pyramid of net production
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- ECOLOGICAL PYRAMIDS Pyramid of productivity ~10% rule - ~10% of
energy at one level transfers to next level Where does the energy
go?
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- Figure 54.10 Energy partitioning within a link of the food
chain
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- Pyramid of biomass standing crop biomass (total dry weight)
Some aquatic systems show inverted pyramids because zooplankton
consume phytoplankton quickly Productivity still upright
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- Figure 54.12 Pyramids of biomass (standing crop)
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- Figure 54.13 A pyramid of numbers
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- NUTRIENT CYCLING Biogeochemical cycles involve both abiotic and
biotic components
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- Figure 54.16 The water cycle
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- Figure 54.17 The carbon cycle
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- CARBON CYCLE Carbon dioxide in atmosphere is lowest in summer
in N. hemisphere and highest in winter. More plants in summer =
less CO 2 in atmosphere Dissolved CO 2 makes carbonic acid (H 2 CO
3 )
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- Increased burning of fossil fuels has increased CO 2 levels,
which leads to global warming. Carbon dioxide absorbs much of the
reflected infrared radiation = greenhouse effect. Without the
greenhouse effect, temperature would be 18C.
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- Figure 54.26 The increase in atmospheric carbon dioxide and
average temperatures from 1958 to 2000 (readings taken from Mauna
Loa, Hawaii)
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- Global Warming A number of studies predict CO 2 will double by
end of 21 st century. Will cause a predicted 2C average global temp
increase Historically, a 1.3 C would make world warmer than any
time in past 100,000 years. Poles probably most affected and polar
ice melting may change our coastlines!
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- Figure 54.18 The nitrogen cycle
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- NITROGEN CYCLE Plants cannot use N 2 (gas). Nitrogen fixing
bacteria convert nitrogen gas into a form of N that plants can use:
ammonium (NH 4 + ) or nitrate(NO 3 - ). Nitrogen fixing bacteria
can live in the soil or in plants called legumes (mutualism).
Legumes include beans, alfalfa, and soy. Denitrifying bacteria
convert nitrate back into nitrogen gas. Without nitrogen fixing
bacteria, plants could not get the nitrogen they need and would
die. All life on earth depends on these bacteria.
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- Figure 54.19 The phosphorous cycle
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- PHOSPHORUS CYCLE Phosphorus is often the limiting nutrient in
lakes. Sewage and runoff provide excess phosphorus. This can cause
eutrophication. This is when a lake develops a high productivity,
which is supported by high rates of nutrient cycling. This leads to
algal blooms, which can suffocate the lake.
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- Figure 54.8 The experimental eutrophication of a lake
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- Figure 54.24 Weve changed our tune
- Slide 119
- BIOLOGICAL MAGNIFICATION Nonbiodegradable substances become
more concentrated in increasing, successive trophic levels. The
biomass at any given level is produced from a much larger biomass
ingested from the level below. Example: DDT caused birds of prey to
lay eggs with thin shells.
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- Figure 54.25 Biological magnification of DDT in a food
chain
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- Chlorinated Hydrocarbons Include DDT, agent orange, PCBs
(polychlorinated biphenyls) They are persistent (i.e., they persist
in the environment for several years) They are non-polar (i.e.,
water-hating) They bioaccumulate (i.e., they concentrate in the fat
of organisms, and their concentration increases as one moves up the
food chain) They are causing a toxic effect at low
concentrations
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- Agent Orange was a defoliant used during the Vietnam War. Agent
Orange is an herbicide that was used during the Vietnam War to
strip the land of vegetation making it easier for the US troops to
see the opposing forces and also to deplete their food supply.
Dioxin is a very toxic chemical within Agent Orange. Dioxin is
believed to be the cause of so much damage and has been linked to
many cancers and birth defects.
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- Dioxin (part of Agent Orange)
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- OZONE DEPLETION Ozone (O 3 ) provides a protective barrier to
UV light. Chlorofluorcarbons react with O 3 and reduce it to O 2,
which makes holes in the layer. Largest hole over Antarctica.
Chlorofluorcarbons come from refrigerants, propellants in aerosol
cans, and in some manufacturing processes.
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- Figure 54.27a Erosion of Earths ozone shield: The ozone hole
over the Antarctic
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- Figure 54.27b Erosion of Earths ozone shield: Thickness of the
ozone layer