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Ecology
Climate
Drives
Ecology
Both the sun and the
seasonal variation of the
earth impact ecology.
The sun is the primary
provider for energy for all
of life.
The seasons (due to the
tilt in the earth’s
axis(~23.5°)) create
variability and change in
the environment.
Water and it’s Impact on Climate
Water is
warmed at the
equator and
flows towards
the poles, where
it cools.
The water can
moderate
climate of
nearby land.
Climate Controls
Terrestrial Biomes
Temperate Broadleaf
Forest
Tundra
Tropical Forest
Savanna
Northern Coniferous
Forest
Desert
Aquatic
Biomes
Make up most of the
largest of all biomes.
Similarly diverse as
terrestrial biomes.
Characterized by their
physical environment:
salt, light, soils, and biotic
factors.
Zonation in Aquatic Biomes
 Zonation depends
upon:
 1) Light
penetration
 2) Distance from
shore and water
depth
 3) Open water vs.
bottom
Different Zones = Different Environment!
Intertidal Zone
Oceanic Pelagic Zone
Benthic Zone
River
Lake
Wetlands
Coral Reef
Estuaries
Ecological Perspective What is being studied?
Population Ecology
Studying what variables affect, influence,
and drive populations of organism.
What drives a population?
Density
Dispersion
Demography
Population Density
Number of individuals in a given area.
Density is constantly in flux; individuals are
being added or removed all the time.
Dispersion:
Spacing of
individuals in
a population
Populations may vary how
they space themselves for
various reasons.
1) Protection
2) Territoriality
3) Mating
4) Feeding
Demography – the vital statistics
and how they change
Birth rates
Death rates
Demographics
of a
population
Done by following a cohort from birth until death.
Each year the number of individuals are determined and the
proportion of surviving members is calculated.
Methods of Displaying
Population Death Rate: Life Table
Life Table
Survivorship Curve
Visual representation of life tables
3 Major types:
I – low early death rates and a steep drop in death at older ages.
II – relatively constant rate of death of the life span of the population.
III – high death rates for young and lower death rates for older individuals.
Population Growth
Food
Reproduce
Grow
In order for a
population to grow
these criteria must
be met to some
degree.
Exponential
Growth
If access to food and
reproduction are unlimited
and there are no restrictions
a population may grow
exponentially.
J-shaped
Maximum rate of increase is
constant, but the number of
individuals over time at a
greater rate.
Seen in populations
introduced to new
environments or those
rebounding.
Logistic Growth
Unlimited resources are
rarely seen. As the population
density increases, resource
availability decreases.
There is a limit to the number
of individuals that the
environment can support:
Carrying Capacity (K).
As K is reached, the
population will remain
relatively constant,
fluctuating slightly.
Logistic Growth
and Real Populations
Population Growth and Natural Selection:
How and why do Populations Grow?
K-selection: Traits that are sensitive to population
density, and are favored at high densities (near K).
r-selection: Traits that maximize reproductive
success. Tactics that allow for fast population
growth.
Population Growth Regulation
• Predation due to
availability
• Waste accumulation
• Disease
• Territoriality
If a birth or death rate
is NOT influenced by
the population density.
 Density Independent
• Competition for
resources
 Density Dependent
If a birth or death rate
is influenced by the
population density.
Ultimately Populations Fluctuate
Yearly – Population Dynamics
Community Ecology
Ecological Niche
An ecological niche is related to an
organism’s “position” in a
community (think job).
The “job” is related to its ability to
rather resources effectively and allow
for that organism to reproduce and
thrive.
2 species competing for the same
resources in the same area cannot
coexist – competitive exclusion
suggests that the slight differences in
the species will lead to some
ecological advantage for one species,
leading to the elimination of the less
fit species.
Resource Partitioning
Community Interactions are Classified
Based on Help, Harm, or no Effect
2) Predation: (+/-)
1) Competition: (-/-)
Different species compete for
the same limited resource
Competitive Exclusion
Ecological niche
One species kills and eats the
other.
Adaptations by predators to
improve success.
Prey often display adaptations
for defense: aposematic
coloration, mimicry, etc.
3) Herbivory: (+/-)
Predation of plants
Most herbivores are invertebrates
Herbivores are adapted to seek out proper
plants
Plants also have defense mechanisms
4) Facilitation: (-/-)
One species has a
positive effect on
another
Symbiosis: 2 or more species in
direct and intimate contact
Parasitism
Mutualism
Commensalism
(+/-)
(+/+)
(+/0)
Community Structure
Species
Diversity
Species
Richness
Relative
Abundance
Community Structure:
Trophic Levels
 Autotrophs (primary producer)
 Herbivores (primary consumer)
 Carnivores (secondary, tertiary, etc. consumer)
 Detritivores (decomposer)
Energetic hypothesis: Food chain length limited
by inefficiency of energy transfer (~10% per
“link”).
Dynamic Stability hypothesis: Long food chains
are less stable due to magnification up each link.
Community Structure: Food
Web
Species with a Large Impact
Dominant Species:
most abundant with
greatest biomass
Keystone Species: not
abundant but exert
great control over
community structure
Disturbance and it’s Impact
on the Community
Disturbance can create
species diversity and
improve the overall
survival of a community.
New York Pine Barrens
Some species rely on
disturbances to complete
their life cycle
Ecological Succession
Ecological succession in Glacier Bay,
Alaska after glacier retreat:
Ecosystem Ecology
Energy Flow and Chemical Cycling
1st Law of
Thermodynamics:
Energy cannot be
created or destroyed
Energy enters
through sunlight
Transferred to other
organisms via food
chains/webs
2nd Law: Entropy
Energy is lost
through heat
Chemical elements are continually cycled through an ecosystem.
Overview of
Energy and
Nutrient Dynamics
in an Ecosystem
Energy limits ecosystem
production!
Without enough energy
input primary producers
cannot support trophic levels
above them.
The same can be said for
various nutrients: limiting
nutrients.
Ecosystem Energy Budget
 Despite the large amount of solar radiation that bombards the
earth daily, only a small amount is used in photosynthesis. ~1%
is used for photosynthesis!
 GPP = amount of energy from light converted to chemical
energy.
 NPP = GPP – energy used by primary producers to make
energy. This is the energy available to consumers – the energy
that moves up the food chain/web.
Energy Transfer
Between Trophic Levels
Much of the energy consumed by an organism
in a trophic level above consumers is lost to heat
through undigested feces, respiration, etc.
~1/6 energy consumed is used for growth
(secondary production).
Trophic
Efficiencies
Amount of product
transferred from one trophic
level to the next.
Much of the energy from one
trophic level is lost due to
heat.
~10% of the available energy
is passed to the next trophic
level.
Similar Trends are Established
for Biomass and Density
But Why???
Biogeochemical Cycles
For each of the biogeochemical
cycles please note:
Biological importance
Forms available to life
Reservoirs – biotic or abiotic
accumulations of a particular
chemical that living things draw
nutrients from and also return the
nutrient to
Key processes – driving factors
for each cycle
Water Cycle