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APESUnit 3
Ecosystems
Ecology
From the Greek words oikos = “house”
and logos = “study of”
– The study of how organisms interact with one
another and with their environment.
YOU SHOULD KNOW!
The difference between eukaryotic and
prokaryotic cells.
The definition of species.
The types of asexual and sexual
reproduction.
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THE NATURE OF ECOLOGY
Ecology is a study
of connections in
nature.
– How organisms
interact with one
another and with
their nonliving
environment.
Species
Organism
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Population
A group of interacting individuals of the
same species.
Each individual will be different due to
genetic diversity.
Each population lives in a particular
habitat spread over an area called a
range.
Population
Community
The total of all populations living and
interacting in a given area.
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Ecosystem
A community and its nonliving
environment.
Animation: Levels of Organization
PLAY
ANIMATION
YOU SHOULD KNOW!
Lower part of atmosphere = troposphere.
Next layer is the stratosphere.
The lowest layers, the hydrosphere and
lithosphere, make up the biosphere.
– Most life exists in the biosphere.
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THE EARTH’S LIFE SUPPORT SYSTEMS
The biosphere
consists of several
physical layers that
contain:
– Air
– Water
– Soil
– Minerals
– Life
Figure 3-6
How is life sustained on Earth?
Three interconnecting factors:
1. The one-way flow of energy from the sun
through the biosphere back into space.
2. Matter cycling
3. Gravity
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Energy Flow
Earth is a closed system.
– Except for the negligible amount of cosmic
matter entering the Earth’s influence and the
miniscule amount of matter that escapes the
planet into space, the Earth is a closed
system.
We already have all of the matter
we will every have.
Energy Flow
Energy, but not matter, is exchanged
between the system and the environment.
Energy Flow
Open Systems
– Both matter and energy are exchanged.
The human body is an open system – matter
(water, food, air) and energy is taken in; waste and
energy is released into the environment.
– Individual organisms depend on both energy
flow and matter flow.
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Animation: Sun to Earth
PLAY
ANIMATION
Absorbed
by ozone Visible
Light
Absorbed
by the
earth
Greenhouse
effect
UV radiation
Solar
radiationEnergy in = Energy out
Reflected by
atmosphere (34% ) Radiated by
atmosphere
as heat (66%)
Heat radiated
by the earth
Heat
Troposphere
Lower Stratosphere
(ozone layer)
Components of Ecosystems
Two major parts of EVERY ecosystem
– Abiotic = the non-living parts
– Biotic = the living parts
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Abiotic Factors
Physical Factors for Land Ecosystems
– Sunlight – intensity, duration
– Temperature – variation, extremes
– Precipitation – Frequency, duration, amount
– Wind – Strength, direction, humidity
Abiotic Factors
Physical Factors for Land Ecosystems
– Latitude
– Altitude
– Fire frequency
– Nature of soil – drainage rate, mineral
content, pH
Abiotic Factors
Physical Factors for Water Ecosystems
– Water currents – flow rate, temperature
– Dissolved nutrients
– Suspended solid material
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Abiotic Factors
Chemical Factors for Ecosystems
– Supply of water and air in soil
– Supply of plant nutrients
– Toxic substances dissolved in soil or water
– Salinity (aquatic ecosystems)
– Level of dissolved oxygen (aquatic
ecosystems)
Animation: Roles of Organisms
in an Ecosystem
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ANIMATION
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Animation: Diet of a Red Fox
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ANIMATION
Abiotic and Biotic Factors
Range of Tolerance
Each population has a range of chemical
and physical conditions that must be
maintained for populations of a particular
species to stay alive and grow, develop,
and function normally.
– Individuals of a population will differ due to
small differences in genetic make-up, age,
and health.
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Law of Tolerance
The existence, abundance, and
distribution of a species in an ecosystem
are determined by whether the levels of
one or more physical or chemical factors
fall within the range tolerated by the
species.
– These may change during an individuals
lifetime.
Range and Habitat
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Law of Tolerance
Threshold Affect
The harmful or fatal effect of a small
change in environmental conditions that
exceeds the limit of tolerance of an
organism or population of a species.
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Threshold Affect
– Example: Swimmers
ear is caused by a
fungus. Changing the
pH in the ear canal
even a little bit can
prevent or increase
the infection.
Limiting Factors
Single factor that limits the growth,
abundance, or distribution of the
population of a species in an ecosystem.
– Example 1: The salinity of the soil in an
estuary may limit plant growth as you get
closer to the ocean.
Limiting Factors
Example 2: A deserts
limiting factor is the
amount of
precipitation.
Organisms must
adapt to preserve
water or perish.
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Limiting Factors
Example 3: Floods
limit food, shelter, and
may bring toxic
materials into an
environment.
Limiting Factors
Example 4: Lack of
shelter can limit the
number of
organisms/size of the
population.
Limiting Factor Principle
Too much or too little of any abiotic factor
can limit or prevent growth of a population
of a species in an ecosystem, even if all
other factors are at or near the optimum
range of tolerance for the species.
– Examples
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Limiting Factor Principle
Important limiting factors are:
– DO (dissolved oxygen)
– Temperature
– Sunlight
– Nutrient availability
– Salinity
YOU SHOULD KNOW!
Autotrophic organisms
Heterotrophic organisms
The role and process of photosynthesis
Definition of herbivore, carnivore, and
omnivore
The difference between aerobic and
anaerobic respiration
Biotic Factors
Three primary types of biotic factors:
1. Producers
2. Consumers
3. Decomposers
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Producers
Autotrophs (Plants)
Most convert sunlight energy to chemical
energy in the form of glucose.
– Photosynthesis
Some do this by chemosynthesisConverting simple compounds from the
environment into more complex nutrients.
– Very special bacteria
Sun
Chloroplast
in leaf cell
Light-dependent
Reaction
Light-independent
reaction
Chlorophyll
Energy storageand release(ATP/ADP)
Glucose
H2O
Sunlight
O2
CO2
6CO2 + 6 H2O C6H12O6 + 6
O2
Animation: Linked Processes
PLAY
ANIMATION
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Producers
Consumers
Organism that cannot synthesize the organic
nutrients it needs and gets its organic nutrients
by feeding on the tissues of producers or of
other consumers; generally divided into primary
consumers (herbivores), secondary consumers
(carnivores), tertiary (higher-level) consumers,
omnivores, and detritivores (decomposers and
detritus feeders).
Primary Consumers
Organism that feeds on all or part of plants
(herbivore) or on other producers.
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Secondary Consumer
Organism that feeds only on primary
consumers.
Tertiary Consumers
Also called higher-level consumers.
Animals that feed on carnivores. They
feed at high trophic levels in food chains
and webs.
– Examples are hawks, lions, bass, and sharks.
Do you agree?
Detritivores
Consumer organism that feeds on detritus,
parts of dead organisms, and cast-off
fragments and wastes of living organisms.
The two principal types are detritus
feeders and decomposers.
– Detritus feeders do not break down their
nutrients to a simple organic compound.
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Decomposers
Organism that digests parts of dead organisms and cast-off fragments and wastes of living organisms by breaking down the complex organic molecules in those materials into simpler inorganic compounds and then absorbing the soluble nutrients. Producers return most of these chemicals to the soil and water for reuse. Decomposers consist of various bacteria and fungi.
Decomposers
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Animation: Matter Recycling
and Energy Flow
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ANIMATION
Animation: Energy Flow
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ANIMATION
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Animation: Prairie Trophic
Levels
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ANIMATION
Fo
od
We
b
Animation: Categories of Food
Webs
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ANIMATION
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Animation: Rainforest Food
Web
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ANIMATION
Animation: Prairie Food Web
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ANIMATION
Energy Flow in an Ecosystem: Losing
Energy in Food Chains and Webs
Ecological
efficiency:
percentage of
useable energy
transferred as
biomass from
one trophic level
to the next.
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Animation: Energy Flow in Silver
Springs
PLAY
ANIMATION
Productivity of Producers:
The Rate Is CrucialGross primary
production
(GPP)
– Rate at which an
ecosystem’s
producers
convert solar
energy into
chemical energy
as biomass.
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Gross primary productivity
(grams of carbon per square meter)
What are nature’s three most
productive and three least
productive systems?
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Average net primary productivity (kcal/m2 /yr)
Open ocean
Continental shelf
Lakes and streams
Estuaries
Aquatic Ecosystems
Extreme desert
Desert scrub
Tundra (arctic and alpine)Temperate grassland
Woodland and shrubland
Agricultural land
Savanna
North. coniferous forest
Temperate forest
Terrestrial Ecosystems
Tropical rain forest
Swamps and marshes
SOIL: A RENEWABLE
RESOURCESoil is a slowly renewed resource that
provides most of the nutrients needed for
plant growth and also helps purify water.
– Soil formation begins when bedrock is broken
down by physical, chemical and biological
processes called weathering.
Mature soils, or soils that have developed
over a long time are arranged in a series of
horizontal layers called soil horizons.
SOIL: A RENEWABLE RESOURCE
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Layers in Mature Soils
Infiltration: the downward movement of
water through soil.
Leaching: dissolving of minerals and
organic matter in upper layers carrying
them to lower layers.
The soil type determines the degree of
infiltration and leaching.
Soil Profiles of the
Principal
Terrestrial Soil
Types
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Animation: Soil Profile
PLAY
ANIMATION
MATTER CYCLING IN
ECOSYSTEMS
Nutrient Cycles: Global Recycling
– Global Cycles recycle nutrients through the
earth’s air, land, water, and living organisms.
– Nutrients are the elements and compounds that
organisms need to live, grow, and reproduce.
– Biogeochemical cycles move these substances
through air, water, soil, rock and living
organisms.
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The Water Cycle
Animation: Hydrologic Cycle
PLAY
ANIMATION
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Water’ Unique PropertiesThere are strong forces of attraction between
molecules of water.
Water exists as a liquid over a wide
temperature range.
Liquid water changes temperature slowly.
It takes a large amount of energy for water to
evaporate.
Liquid water can dissolve a variety of
compounds.
Water expands when it freezes.
Effects of Human Activities
on Water Cycle
We alter the water cycle by:
– Withdrawing large amounts of freshwater.
– Clearing vegetation and eroding soils.
– Polluting surface and underground water.
– Contributing to climate change.
The Carbon Cycle:
Part of Nature’s Thermostat
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Animation: Carbon Cycle
PLAY
ANIMATION
Effects of Human Activities
on Carbon Cycle
We alter the carbon cycle by adding excess CO2
to the atmosphere through:
– Burning fossil fuels.
– Clearing vegetation faster than it is replaced.
The Nitrogen Cycle:
Bacteria in Action
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Animation: Nitrogen Cycle
PLAY
ANIMATION
Effects of Human Activities
on the Nitrogen Cycle
We alter the nitrogen cycle by:
– Adding gases that contribute to acid rain.
– Adding nitrous oxide to the atmosphere through
farming practices which can warm the
atmosphere and deplete ozone.
– Contaminating ground water from nitrate ions in
inorganic fertilizers.
– Releasing nitrogen into the troposphere through
deforestation.
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Effects of Human Activities
on the Nitrogen Cycle
Human activities
such as
production of
fertilizers now fix
more nitrogen
than all natural
sources
combined.
Figure 3-30
The Phosphorous Cycle
Animation: Phosphorous Cycle
PLAY
ANIMATION
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Effects of Human Activities
on the Phosphorous Cycle
We remove large amounts of phosphate from
the earth to make fertilizer.
We reduce phosphorous in tropical soils by
clearing forests.
We add excess phosphates to aquatic
systems from runoff of animal wastes and
fertilizers.
The Sulfur Cycle
Animation: Sulfur Cycle
PLAY
ANIMATION
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Effects of Human Activities
on the Sulfur Cycle
We add sulfur dioxide to the atmosphere by:
– Burning coal and oil
– Refining sulfur containing petroleum.
– Convert sulfur-containing metallic ores into free
metals such as copper, lead, and zinc releasing
sulfur dioxide into the environment.
The Gaia Hypothesis:
Is the Earth Alive?
Some have proposed that the earth’s various
forms of life control or at least influence its
chemical cycles and other earth-sustaining
processes.
– The strong Gaia hypothesis: life controls the
earth’s life-sustaining processes.
– The weak Gaia hypothesis: life influences the
earth’s life-sustaining processes.
Biodiversity Loss and Species
Extinction: Remember HIPPOH for habitat destruction and
degradation
I for invasive species
P for pollution
P for human population growth
O for overexploitation