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Visualizing Environmental Science
How Ecosystems Work
Chapter 5
Chapter
Chapter77
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Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.
What is Ecology?
• The study of the
interactions among
organisms and
between organisms
and their abiotic
environment
• Biotic and abiotic
© 2014 John Wiley & Sons, Inc. All rights reserved.
What is Ecology?
• Levels of organization
– Population: a group of
organisms of the same
species that live in the same
place at the same time
– Communities: all the
populations of different
species that live and interact
together within an area at
the same time; note the
tidal pool community
– Ecosystem: community and
physical environment
© 2014 John Wiley & Sons, Inc. All rights reserved.
What is Ecology?
• A landscape is a region
that includes several
interacting ecosystems
• Biosphere– layer of Earth
that contains all living
organisms
– Compare atmosphere,
lithosphere , hydrosphere
© 2014 John Wiley & Sons, Inc. All rights reserved.
The Flow of Energy Through Ecosystems
• Energy—the ability to do work
– Potential energy—stored energy
– Kinetic energy—energy of motion
• Thermodynamics—the study of energy and its
transformations
– First and second law of thermodynamics
© 2014 John Wiley & Sons, Inc. All rights reserved.
The First Law of Thermodynamics
• Energy cannot be
created or destroyed
• Total energy content
always the same
• Energy can change
from one form to
another
– Photosynthesis—solar
energy converted to
chemical energy
© 2014 John Wiley & Sons, Inc. All rights reserved.
The Second Law of Thermodynamics
• The amount of usable
energy in the universe
decreases over time as
some is lost as heat
– Heat—less usable and
disorganized form of energy
• Entropy—a measure of
this disorder
© 2014 John Wiley & Sons, Inc. All rights reserved.
The Flow of Energy Through Ecosystems
• Producers manufacture large
organic molecules from simple
inorganic molecules
– Producers are potential food for
other organisms
– This moose is an herbivore or a
primary consumer, feeding on
the chemical energy stored in
grasses
© 2014 John Wiley & Sons, Inc. All rights reserved.
The Flow of Energy Through Ecosystems
• Consumers are animals that
consume other organisms
• Detritivores—consumers
such as this crab eat organic
matter called detritus
• Decomposers—bacteria and
fungi that break down dead
and decaying organisms
© 2014 John Wiley & Sons, Inc. All rights reserved.
The Flow of Energy Through Ecosystems
• Energy flow—the passage of energy in a one-way
direction through an ecosystem, occurs in food chains
• Trophic level—each level in a food chain
• Energy is lost as heat along the way, thus the number
of steps in a food chain is limited and less energy is
available for organisms at the higher trophic levels
© 2014 John Wiley & Sons, Inc. All rights reserved.
The Flow of Energy Through Ecosystems
• Ecological pyramids graphically
represent the relative energy
values of each trophic level
• Pyramids of energy illustrate
how energy dissipates into the
environment as it moves from
one trophic level to the next
© 2014 John Wiley & Sons, Inc. All rights reserved.
Ecosystem Productivity
• Gross primary productivity
(GPP) is the rate at which
energy is captured during
photosynthesis
• Net primary productivity
(NPP) is the amount of
biomass found in excess of
that broken down by a plant
during cellular respiration
– NPP is expressed in grams of dry
matter per square meter per
year for the selected ecosystems
© 2014 John Wiley & Sons, Inc. All rights reserved.
The Cycling of Matter in Ecosystems
• Biogeochemical cycles
– Matter—the material of which organisms are
composed
– Humans have GREAT influence on them
© 2014 John Wiley & Sons, Inc. All rights reserved.
The Cycling of Matter in Ecosystems
• The carbon cycle
– The global movement of carbon between the
abiotic environment (atmosphere, ocean) and
organisms
– Atmosphere/ocean  photosynthesis  cellular
respiration/combustion/decomposition 
atmosphere/ocean
• Carbon is an essential component of organisms’
molecules
• Also essential component of abiotic environment
© 2014 John Wiley & Sons, Inc. All rights reserved.
Carbon Cycle
• 0.04% of the atmosphere
• Needed to make proteins
and carbohydrates
• Present in several forms
such as CO2, HCO3-, and
CaCO3
• Fossil fuels, coal, oil and
natural gas are deposits of
carbon compounds
• Photosynthesis fixes carbon
from CO2 into
carbohydrates
© 2014 John Wiley & Sons, Inc. All rights reserved.
The Hydrologic Cycle
• Water circulates among the
ocean, land, and atmosphere
• Creates a renewable supply of
water for terrestrial
organisms
– Runoff is water from land to
rivers and lakes
– Watersheds are areas of land
where runoff drains
© 2014 John Wiley & Sons, Inc. All rights reserved.
The Nitrogen Cycle
• Nitrogen is an essential
component of proteins and
nucleic acids
• Atmosphere is 78% nitrogen
gas
• Five steps in which nitrogen
cycles between the abiotic
environment and organisms
–
–
–
–
–
Nitrogen fixation
Nitrification
Assimilation
Ammonification
Denitrification
© 2014 John Wiley & Sons, Inc. All rights reserved.
The Cycling of Matter in Ecosystems
• Nitrogen-fixing bacteria
carry out nitrogen fixation in
soil and aquatic
environments
– This bacteria is fixing nitrogen
in the nodules of a pea plant’s
root
• Photochemical smog and
acid deposition are nitrogenbased air pollutants
© 2014 John Wiley & Sons, Inc. All rights reserved.
The Sulfur Cycle
• Most sulfur is underground in
sedimentary rocks and
minerals
• Animals get sulfur from plant
protein
• Sulfur gas is a minor part of
the atmosphere, but
movement of sulfur is
substantial
• Bacteria-driven cycle
• Burning coal releases sulfur,
which causes acid deposition
© 2014 John Wiley & Sons, Inc. All rights reserved.
The Phosphorous Cycle
• No atmospheric component
• Cycles between land and
organisms
• Phosphorous in soil is
absorbed by plant roots
– Necessary to make nucleic acids
and ATP
• Phosphorus in fertilizers can
cause eutrophication, as in
Lake Washington (chapter
•
opener)
Anthropogenic loss of terrestrial
phosphorus
© 2014 John Wiley & Sons, Inc. All rights reserved.
Ecological Niches
• Niche
– The totality of an organism’s adaptations, its use
of resources, and the lifestyle to which it is fitted
• Describes the place and function of an organism within
the ecosystem
• The “way of life of an organism”
• Habitat
– Part of an organism’s niche, the place where the
organism lives
© 2014 John Wiley & Sons, Inc. All rights reserved.
Ecological Niches
• Fundamental niche—the
potential, idealized niche
• Realized niche—the actual
niche an organism
occupies
• While the fundamental niches
of these two lizards initially
overlap, the brown anole outcompeted the green anole,
restricting is realized niche
• Generalists vs. specialists
© 2014 John Wiley & Sons, Inc. All rights reserved.
Resource Partitioning
• One way species avoid or
reduce niche overlap
• Serves to reduce
competition for resources
• Resource partitioning of five
warbler species
– Each species spends most of
their time feeding in different
portions of the tree
© 2014 John Wiley & Sons, Inc. All rights reserved.
Interactions Among Organisms
• Symbiosis—two species
living in close association
• Symbiosis is the result of
coevolution, as seen in this
honeycreeper’s curved bill
perfectly suited to sip
nectar from the tubular
flowers
© 2014 John Wiley & Sons, Inc. All rights reserved.
Interactions Among Organisms
• There are three main types
of symbiosis
– Mutualism, where both
organisms benefit
• The ant obtains food and shelter
from the plant and in turn,
protects the plant from predators
– Commensalism, where one
benefits but the other is
unaffected—neither harmed
nor helped
– Parasitism, one benefits at
the expense of the other
© 2014 John Wiley & Sons, Inc. All rights reserved.
EnviroDiscovery
Bee Colonies Under Threat
• Since 2006, major losses to bee
colonies, referred to as colony
collapse disorder (CCD)
– CCD is the result of pesticides,
pathogens, parasites, and viruses
such as Israeli acute-paralysis
virus
• Bees are important pollinators
and many crops are threatened
by bee declines
– Pear trees in China being hand
pollinated
© 2014 John Wiley & Sons, Inc. All rights reserved.
Interactions Among Organisms
• Predation—the consumption
of one species (prey) by
another species (predator)
– Coevolutionary “arms race”
as predators evolve to better
catch prey and prey evolve to
better escape predator
– The cheetah sprints at high
speeds to catch prey
– The goldenrod spider uses
camouflage to ambush prey
© 2014 John Wiley & Sons, Inc. All rights reserved.
Avoiding Predation
• Social behavior can decrease
predation such as adult
meerkats standing guard at
their burrow, ready to alert
the group of danger
• Chemical defense in prey such
as poison glands and bright
warning colors
• Camouflage to hide from
predators such as this Indian
leaf butterfly
© 2014 John Wiley & Sons, Inc. All rights reserved.
Competition
• The interaction among
organisms that vie for the same
resources in an ecosystem,
such as food or living space
– Intraspecific competition
– Interspecific competition
© 2014 John Wiley & Sons, Inc. All rights reserved.
Competition
• Keystone species, such as the
gray wolf, is crucial to the
maintenance of the ecosystem
– Not the most abundant, but have
influence on entire ecosystem
– Note the reintroduction of the
wolf in 1995 affected the elk
population
© 2014 John Wiley & Sons, Inc. All rights reserved.
Keystone Species
• Another keystone species,
the sea otter exerts their
influence by changing
competitive relationships.
• They help maintain balance
in an ecosystem.
3-31
Monterey Bay, California
Keystone Species