ECOLOGY

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ECOLOGY Part 2
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What is Ecology?
The study of biological organization at and
above the level of the organism. (one definition)
What are levels of organization?
Biosphere Ecosystem Community Population Organism
Organ Tissue Cell Organelle Molecule
Ecology
2-7
Note species is not on this list
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Populations/Communities
Similar species can co-exist more readily if they
utilize different portions of shared niche axes
have different niches (determined by traits)
Coastal wetland
So, an organisms integrated traits (genes) allow
success or determine failure of a population in
any particular ecosystem
Both the possibilities and limits for survival
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Communities
What organizes biology above the level of the
population?
Communities Ecosystems - Primarily the
interactions of populations with each other and
the abiotic environment (another definition of
ecology).
Most common interaction? Eating.
In economics follow the money, in ecology,
follow the food
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Communities
Community the array of interacting populations
in a place.
Major insight to a large extent, the question
is - who eats who?
Communities are analyzed by the network of eating
interactions, ultimately the overall food web or
trophic structure.
2-16/2-18 A marine food web
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Species Interactions classified by pairwise
effects (,-, 0)
Competition (-/-) use same resource, depletion or
combat Predation (/-) one eats(kills) the
other Parasitism (/-) one eats (partially) the
other Mutualism (/) each benefits from the
other Commensalism (/0) hard to verify, e.g.
epiphytes (0,0) meaningless, seldom see (-,0)
why?
Eating still the key underlying theme
competition, predation, parasitism obvious.
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Even mutualism often about eating (or not being
eaten) usually involves a trade (food, defense)
Plants major mutualisms - nutrition
myccorhizae (fungus), nitrogen fixers (bacteria),
trade nutrient and carbohydrate
4-4/4-2
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Flowers mutualism? Angiosperm flowers attract
insects with rewards, often food (nectar,
pollen), gain reproduction
In some flowers, the rewards are questionable
Many mutualisms reveal these kinds of subtle
antagonisms when studied closely.
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Communities
A food web consists of a complex set of
interconnected transformations. Similar in this
way to a biochemical pathway.
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Communities
A food web consists of a complex set of
interconnected transformations. Similar in this
way to a biochemical pathway.
One important difference is, there is currently
no evidence that natural selection operates on
the overall food web as it does on whole
organisms. A community is more like a free
market economy, structured only by the
interactions.
Communities are assembled by the component
species
Note potential for re-assembly
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Around my barn - Dillon Bustin
Down in the cornfield see the deer Each one
chewing on a yellow ear And every squirrel thats
ever been born Wants to make a living off the
little corn That I get to my barn, get to my
barnyard
When the hound begins to howl And Ive not heard
a hooting owl When the chickens begin to
squawk Thats the time Ill take a walk
Refrain around my barn, around my barnyard
All the milk that my milk cow makes Gets drunk
up by a long milk snake You may not believe what
I say is true But he aint eating mice Im
telling you Out in my barn, out in my barnyard
Could be the wind in the trees Could be a rabbit
or a groundhog sneeze Eating the peppers in my
garden spot Hed better hope that I am
not Around my barn, around my barnyard
Could be a cloud across the moon Could be a fox
or a sly raccoon Coming down to make a meal He
dont know the way I feel About my barn, about
my barnyard
Lindy tells me treat them like brothers I told
her let them eat each other Its what they done
before I come What theyll do before Im
done With my barn, done with my barnyard
You ask me whats dirty trick Skinny old weasel
in among the chicks And when hes done gnawing
their legs An old skunk come and hell suck the
eggs That are left in my barn, left in my
barnyard
Well I never expected life to be Simple or easy
or completely free But I did not think that Id
have to fight To get one drink or a single
bite Of food from my barn, food from my barnyard
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Communities
Types of eating
Herbivory plant eating Carnivory meat
eating Omnivory mixed diets Detritivory
eating dead stuff Photosynthesis sun eating
Major insight different food webs share a
general structure, with photosynthesizers as the
foundation
The rest of the food web depends on the
photosynthesizers
This led to the concept of ecosystem
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Communities/Ecosystems
Simplified web food chain
Photosynthesizers called producers, herbivores
carnivores called consumers
Ecosystem ecologists aggregate (simplify) webs to
focus on key dynamics and system properties
2-15/2-17
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Ecosystems
Generalization called attention to a major
component of the ecosystem previously ignored -
decomposers
The unasked question where does all the dead
stuff go?
and incidentally what are plants eating?
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2-13/2-14
Why do decomposers exist?
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Ecosystems
The most general concept of ecosystem includes
decomposers as main component
Also chemicals, or nutrients (since this is
mostly food for the producers)
Note the difference in emphasis compared to the
food web
2-14/2-15
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Ecosystems
This is a dynamic equilibrium (outputs inputs)
Components may stay fairly stable, but
Energy flows through the ecosystem,
driving Material cycles within
Resource use by individuals (eating) drives these
dynamics
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This is a basic picture of an ecosystem
Energy Materials
Both energy and materials are transferred
together
Consumers
Heat
Heat
Decomposers
Producers
Heat
except here
Nutrients
Sun
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To a decent first approximation, you can stick
our kingdoms into this basic picture of ecosystems
Aquatic (water-based)
Terrestrial (land-based)
This suggests a deep connection between evolution
and ecology
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Ecosystems nutrient cycling
7-A/2-22
Decomposers are a complex of many species in an
OM matrix
Terrestrial ecosystems - soil
Rock particles organic matter
Aquatic systems
Dissolved organic matter (DOM) Sediments
Soils sediments can take 100s of years to
develop
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Ecosystems nutrient cycling
What are nutrients?
In addition to CO2, light and water, producers
also need various other essential elements
Nitrogen (N), Phosphorus (P), Potassium (K),
Magnesium (Mg), Calcium (Ca) and various others
(Iron, Boron, Nickel, etc.) Why?
Chlorophyll
What controls nutrients?
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Ecosystems nutrient cycling
Nutrient Cycling
Reservoirs. Most elements originally come from
rock the earths crust, via weathering. Except
Nitrogen - atmosphere
In most systems, most elements used by producers
come from decomposition which recycles the
nutrients.
Nutrients have both long and short term cycles
Short term (fast) community to dead organic
matter (detritus OM) via decomposition to the
nutrient pool back to community
Long term (slow) from system to reservoir, back
to system
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Ecosystems nutrient cycling
In addition to water and carbon cycles, life
creates cycles within ecosystems of essential
nutrients for producers
Phosphorus cycle is typical of most elements
rock reservoir, organic matter derived
available pool (also K, Ca, Mg, etc.)
2-22/2-28
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Ecosystems nutrient cycling
Nitrogen Cycle
Reservoir N2 gas in atmosphere 79
Nitrogen fixation (certain bacteria) converts
N2 to organic form energetically expensive
Decomposition releases nitrogen to available
forms (ammonium (NH4) and nitrate (NO3))
Producers take up available N so convert it back
to organic Nitrogen completing the short cycle
N2 gt OrgN gt Available N
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Ecosystems nutrient cycling
Some bacteria use NO3 for energy, releasing N2
gas Denitrification. This is the cause of our
N2 atmosphere
Percent Composition of the
Atmosphere   CO2 O2 N2   Venus 96.5 trace
3.5   Mars 95 0.13 2.7   Earth 98 0.0 1.9 (
w/o life)   Earth 0.03 21 79 (w/ life)
This creates the longer cycle
N2 gt OrgN gt Available N gt N2
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Ecosystems nitrogen cycling
2-21/2-27
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Ecosystems nutrient cycling
These nutrient cycles can be added to the water
and carbon/oxygen cycles covered earlier.
2-20/2-26
2-19/2-25
Together they describe the global fluxes of major
materials regulating ecosystem production
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Ecosystems
Trophic Structure The energy pyramid
Energy flows through the ecosystem from sun to
space
Heat
Heat
Energy is transformed by photosynthesis from
light to chemicals (e.g., sugar)
Heat
Energy of chemicals is transformed from producers
to consumers and to decomposers
Energy is lost in all transformations as heat,
generating EM waves
-Respiration (can be gt90 of energy taken
in) -The energy transformations are not 100
efficient
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Ecosystems - energy
2-17/2-19
The flow of energy up is a diminishing one
Only a portion of energy flowing into a trophic
level is transferred to the next higher level.
Ecological Efficiency about 10 (2-40)
This limits trophic levels to 4 or 5
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Ecosystems
Primary Productivity
Ecosystems depend on producers for energy
Primary productivity is variable throughout the
world
What controls this variability?
Global chlorophyll levels winter 2004
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Ecosystems - productivity
Net Primary Productivity (NPP)
Gross Primary Productivity (GPP) Respiration
(R)
NPP measures the ecosystems capacity to support
life (producers, consumers, decomposers)
Units kcal/m2/year energy/area/time
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Ecosystems - productivity
2-18/2-21
Ecosystems differ in NPP area of systems not
shown (e.g., ocean)
Why?
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Biomes
Globally, there is a strong correlation between
NPP, total plant biomass, and precipitation.
We know that NPP is dependent on temperature,
water, light, CO2 and many nutrients.
Why is water so important?
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Biomes
How plants work
Leaf light, CO2 Root water, nutrients
air
But water is lost in taking up CO2 more
water more CO2
soil
And water increases decomposition rate in soil
more water more nutrients
Result Water is both a resource and a controller
of CO2 and nutrients. More rain has several
benefits.
Temperature? higher temp more water lost
per C lower temp shorter growing season
(less liquid water)
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Biomes
In general NPP controlled by light and water.
Light is relatively un-varying water is
variable Variation in NPP primarily due to
water
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Biomes
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Biomes
So precipitation and temperature are the master
controllers of plant production (NPP)
Distribution of climates.
Precipitation and temperature climate
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Biomes
Climate controls NPP
Distribution of chlorophyll
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Biomes
niche diagram
3-6/3-7
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Ecology summary

• The biosphere consists of diverse linked
  ecosystems
• Eating by individual organisms, including
  photosynthesis, drives primary production,
  trophic structure, and decomposition. The
  balance of nature reflects a balance of
  conflicting interests of individuals.
• Ecosystems consist of 4 main components
  producers, consumers, decomposers, nutrients.
  Fit of kingdoms to these compartments suggests a
  deep connection of evolution and ecology.
• Energy flows from the sun through the ecosystems
  and into space, powering materials (elemental)
  cycles within ecosystems.
• 5. In terrestrial systems, variation in climate
  controls variation in NPP, and therefore biome
  distribution.

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End Ecology
End Ecology