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Chapter 3
Ecosystems: What Are
They and How Do They
Work?
THE NATURE OF ECOLOGY
 Ecology
is a study
of connections in
nature.

How organisms
interact with one
another and with
their nonliving
environment.
Figure 3-2
Organisms and Species
 Organisms,
the different forms of life on
earth, can be classified into different species
based on certain characteristics.
Figure 3-3
Classification of Life
(Did King Phillip Come Over From
Great Spain?)
 Domain
 Kingdom
 Phylum
 Class
 Order
 Family
 Genus
 Species
Microorganisms Importance
 Fix
nitrogen
 Make foods
 Break down wastes
 Provide oxygen
 Break down toxins in water
 Source of antibiotics
 Clean up oil spills
 Control diseases (natural pest control)
Connect: Populations, Communities,
and Ecosystems
Populations
 Genetic

diversity
In most natural
populations
individuals vary
slightly in their
genetic makeup.
Figure 3-5
Life on Earth is sustained by…
•Troposphere: 78%
Nitrogen and 21%
Oxygen
•Stratosphere:
GOOD ozone (O3)
•Lithosphere:
nonrenewable
resources and
minerals
Life on earth is sustained by…

Solar energy (low
quality), the cycling
of matter (fixed amount),
and gravity (maintain
atmosphere) sustain
the earth’s life.

Can energy be
recycled?
Figure 3-7
Solar Energy and the Earth
What does solar
energy do that is
important for life
on Earth?
Greenhouse Effect

solar radiation enters as visible light and degraded
to infrared radiation
 encounters the greenhouse gases in the
troposphere.
 The greenhouse gases absorb the IR waves and
then emit more IR waves (even longer
wavelengths)
 this speeds up the air molecules (gain KE) and this
heats the troposphere and earth’s surface.
What are ECOSYSTEM
COMPONENTS?

Life exists on land systems called biomes and in freshwater
and ocean aquatic life zones.
Figure 3-9
Nonliving and Living Components of
Ecosystems
 Ecosystems
consist of nonliving (abiotic) and
living (biotic) components.
Figure 3-10
Factors That Limit Population Growth

Range of Tolerance and Availability of matter and
energy resources (limiting factors) can limit the
number of organisms in a population.
 Population control=sustainability
Figure 3-11
Biotic Factors in an Ecosystem
 Most
PRODUCERS capture sunlight to
produce carbohydrates by photosynthesis:

Autotrophs (plants, algae, phytoplankton, plant-like protists)
Producers: cont.
 Chemosynthesis:

Some organisms such as deep ocean bacteria
draw energy from hydrothermal vents and
produce carbohydrates from hydrogen sulfide
(H2S) gas .
Consumers: Eating and Recycling to
Survive
 Consumers
(heterotrophs) get their food by
eating or breaking down all or parts of other
organisms or their remains.

Herbivores
• Primary consumers that eat producers

Carnivores
• Primary consumers eat primary consumers
• Third and higher level consumers: carnivores that eat
carnivores.

Omnivores
• Feed on both plant and animals.
Decomposers and Detritivoresconsumers TOO!


Decomposers: Recycle nutrients in ecosystems.
Detritivores: Insects or other scavengers that feed
on wastes or dead bodies.
Figure 3-13
Aerobic (with Oxygen) and Anaerobic
Respiration: Getting Energy for Survival

breaking down carbohydrates and other organic
compounds to obtain the energy

This is usually done through aerobic respiration.
 The opposite of photosynthesis
Cont.
 Anaerobic


respiration or fermentation:
Some decomposers get energy by breaking
down glucose without oxygen.
The end products vary based on the chemical
reaction:
•
•
•
•
Methane gas
Ethyl alcohol
Acetic acid
Hydrogen sulfide
Two Secrets of Survival: Energy Flow
and Matter Recycle
 An
ecosystem
survives by a
combination of
energy flow and
matter recycling.
Figure 3-14
Biodiversity maintains Ecosystems
 We

are losing biodiversity due to HIPPO:
H for habitat destruction and
degradation-leading cause




I for invasive species- 2nd leading cause
P for pollution leading to global climate change.
P for human population growth that leads to
resource consumption
O for overexploitation- overhunting and
overconsumption
• Who is Aldo Leopold?
ENERGY FLOW IN ECOSYSTEMS


Food chains and webs show how eaters, the eaten, and the
decomposed are connected to one another in an ecosystem.
Energy flows in 1 Direction!
Figure 3-17
 Interconnected
food chains make
up a complicated
food web.
 Which trophic
level would there
be more
organisms, 1st or
4th? Why?
Figure 3-18
Energy Flow in an Ecosystem: Losing
Energy in Food Chains and Webs
accordance with the 2nd law of
thermodynamics, there is a decrease in the
amount of energy available to each
succeeding organism in a food chain or web.
 In
10% RULE in energy flow

Ecological
efficiency:
percentage of
useable energy
transferred as
biomass from one
trophic level to the
next.
 Where
does the
energy go?
Figure 3-19
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
(referred to as reservoirs).
The Hydrologic Cycle
Figure 3-26
Water’ Unique Properties
 There
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

PS and CR recycle
 Ocean stores (dissolved Carbon dioxide)
 Shells of marine life store (Calcium carbonate)
 Limestone stores
 Fossil Fuels store until BURNED
Figure 3-27
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 (less PS).
Figure 3-28
The Nitrogen Cycle:
Bacteria in Action
Figure 3-29
Explanation of the chart
2
processes FIX atmospheric nitrogen into a
usable form:
• Lightning
• Nitrogen-fixing bacteria in soil


NITROGEN FIXATION:
• FIX N2NH3 (ammonia)NH4+ (ammonium) that can
be taken up by plants
NITRIFICATION
• NH3 and NH4+ is converted to nitrite,NO2- TOXIC TO
PLANTS and then nitrate, NO3- GOOD FOR PLANTS
AND ANIMALS WHO EAT PLANTS
Cont.
 Plants
and animals put nitrogen back into
environment through wastes and when they
die.


AMMONIFICATION is when decomposer bacteria
convert this organic material from their death into simpler
nitrogen-containing inorganic compounds like ammonia
(NH3) and ammonium (NH4+).
DENITRIFICATION is when specialized bacteria in wet
areas convert ammonia and ammonium back into
nitrogen gas and nitrous oxide gas (both GHG’s).
Effects of Human Activities
on the Nitrogen Cycle
 We




alter the nitrogen cycle by:
Adding gases (NO, nitric oxide, from burning fuels) that
contribute to acid rain.
Adding N2O, nitrous oxide to the atmosphere through
fertilizers added to crops which can warm the atmosphere
and deplete ozone.
Contaminating ground water from nitrate ions in inorganic
fertilizers disrupting aquatic life.
Releasing nitrogen into the troposphere through
deforestation.
The Phosphorous Cycle- doesn’t enter
AIR
Figure 3-31
Explanation of chart

Phosphorus is found as phosphate ions (PO43-) in rock and
soil. As water runs over rocks the phosphates mix into the
water and ends up in the ocean where it settles to the ocean
floor.



Plants take phosphates directly from the soil or water
and build macromolecules with it.
Animals take in plants and excrete extra phosphorus
in urine.
Phosphorus is often a LIMITING FACTOR for plants
because there is little in soil (unless added from
fertilizer) and is only slightly soluble in water.
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
Figure 3-32
Explanation of chart





Found as sulfate (SO42-)in rocks and minerals and salts
buried deep under ocean sediments
Released from volcanoes as hydrogen gas (H2S) and sulfur
dioxide (SO2)
Sulfate salts like ammonium sulfate are released by sea
spray, dust storms, and forest fires
Plants absorb sulfate ions and incorporate them into their
macromolecules
Marine bacteria produce dimethyl sulfide (DMS) which
begins condensation thus can affect climate

DMS is converted to SO2 and SO3 and then to sulfuric acid
(H2SO4)= ACID RAIN
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.
Due to the high need for producers to maintain
our growing population you must consider
 Gross
primary
production
(GPP)

Rate at which an
ecosystem’s
producers
convert solar
energy into
chemical energy
as biomass.
Figure 3-20
AND
Net Primary Production (NPP)
 NPP

= GPP – R
Rate at which
producers use
photosynthesis to
store energy minus
the rate at which they
use some of this
energy through
respiration (R).
Figure 3-21
Why do GPP and NPP matter?

As humans take up more land and degrade more
forest ecosystems, we lower the earth’s possible
GPP and NPP.
• Estimates say that humans and domesticated animals
take up 98% of earth’s biomass and wildlife only 2%.
OUT OF BALANCE!
• Relate to the biomass pyramid.
 What
are nature’s three most productive and
three least productive systems?
Figure 3-22
What is the Gaia Hypothesis?
Chapter 7
Community Ecology
What are important characteristics of a
community?



Species diversity- the number of different species
it contains (species richness) combined with the
abundance of individuals within each of those
species (species evenness)
Niche structure- # of niches, differences in
niches, and how individuals in different niches
interact
Geographical location- closer to equator= more
diversity usually due to constant conditions near
tropics
SPECIES RICHNESS IN AFRICA
What are the types of species in a
community?


Native species- normally live and thrive in a
particular community
Nonnative species- invasive and alien species
are introduced into a community.
• NOT ALWAYS BAD (chickens, cattle) but CAN BE
(African “killer” bee intended to help honey production
increase)

Indicator species- serve as early warnings of
damage to a community
• Example: trout for water quality because they need
clean water with lots of dissolved oxygen
• Ex. Birds and butterflies: greatly affected by habitat
loss and chemical exposure
• Ex. Amphibians: GOOD INDICATOR SPECIES
Why are Amphibians Vanishing?
 Because
they live part of life in water and part
on land so tell about water, soil, and air quality.
• Affected by: pollution (pesticides), habitat loss, drought,
increase UV light, climate change, overhunting Figure 7-3

Keystone species- a species that greatly affects
other species in the community.
• Ex. Pollinators like bees and butterflies
• Ex. Top predators like wolves, lions, alligators, some
sharks

Foundation species- play a major role in shaping
communities by creating and enhancing their
habitats in ways that benefit other species.
• Ex. Elephants that push over trees and allow smaller
grasses to grow that allow grazers like antelope to eat.
• Ex. Bats and birds that move seeds around by eating
and dropping them in feces to re-grow a forest that has
been depleted.
What types of interactions do species have?

Interspecific competition- ability of one species to
become more efficient in acquiring resources than
another. POPULATION SIZE CONTROL
1. Resource partitioning- adaptations evolved that reduce
competition that allow species to share resources by
evolving specialized traits.


Example: hawks feed during day, owls at night
Ex. Lions take larger prey, leopards take smaller
Resource Partitioning
 Each
species minimizes
competition with the others
for food by spending at
least half its feeding time
in a distinct portion of the
spruce tree and by
consuming somewhat
different insect species.
Figure 7-7
Niche Specialization
 Niches
become
separated to
avoid competition
for resources.
Figure 7-6
Interactions of species cont.

Predation- predators feed on prey. POPULATION CONTROL
AND NATURAL SELECTION (makes population stronger)
• Ex. Lions feed on zebras= predator-prey relationship

Parasitism- parasite benefits by living in or on the host who is
harmed. POPULATION CONTROL
• Tapeworms, ticks, fleas, mistletoe, cowbirds

Mutualism- both species benefit
• Honeybees, caterpillars, butterflies pollinate flowers and feed on nectar
• Clownfish and sea anemone
• Fungus with plant roots that makes Mycorrhizae. Fungus feeds on plant
roots but plant has more roots for water uptake.

Commensalism- benefits one species but has little to no effect on
the other.
• Birds and trees- birds have habitat
• Orchids that grow on trees in tropics get more light and stable place to
grow but don’t affect tree.
PREDATION
 Some
prey escape
their predators or
have outer
protection, some
are camouflaged,
and some use
chemicals to repel
predators.
Figure 7-8
Mutualism: Win-Win Relationship
 Two
species
can interact in
ways that
benefit both of
them.
Figure 7-9
Commensalism: Using without Harming
 Some
species
interact in a way
that helps one
species but has
little or no effect
on the other.
Figure 7-10
Ecological succession: the gradual change
in species composition of a given area

Primary succession: the gradual establishment of biotic
communities in lifeless areas where there is no soil or
sediment.
• No soil present, exposed rock, lava, concrete
• Lichens or mosses attach to rock and break them
down by releasing acids, and catch soil particles
floating in wind (millions of years to produce fertile soil)

Secondary succession: series of communities
develop in places containing soil or sediment.
• Begins in an area where the community has been
disturbed or destroyed (forests burned, farm
abandoned, heavily polluted streams
How do living systems maintain stability?





Adaptations in response to changing environments (not
within an individual’s lifetime but over generations)
Persistence- ability of a living system to resist being
disturbed
Constancy- ability of a living system to keep its numbers
within the limits imposed by natural resources
Resilience- ability of living system to bounce back and
repair damage after a disturbance that it not too drastic
Diversity
Function within the 4 scientific principles of
sustainability:
•
•
•
•
Depend on solar energy
Participate in chemical cycling
Have a diversity of types and species
Populations are controlled by interactions among their
species
Mt. St. Helens in Washington erupted
in 1980 and was a model for
ecological succession.