Download 8Core Chpater 12short

12.1 Ecology is the study of organisms in
their environments
• Ecology is the study of how organisms interact
with each other and with their environment.
Ecologists make verifiable
observations using the
discovery approach.
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Hypothesis-driven ecology
science may be conducted
in the field or in the lab.
12.1 Ecology is not environmentalism
• Environmentalism is a broad philosophy
and social movement that seeks to
maintain environmental quality.
• The science of ecology provides the basis
for understanding environmental
problems.
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Rachel Carson and “Silent Spring”
– Rachel Carson
• Was one of the first
ecologists to perceive the
global dangers of pesticide
abuse.
• Helped initiate our current
environmental awareness
with her book Silent Spring.
•
•
The modern environmental movement was
catalyzed by Rachel Carson.
She was concerned about the effects of
pesticides on the environment
– The pesticide DDT, which
improved agricultural
production,
• Was developed in the
1950s.
• Was determined to have
harmful side effects.
•
For example the American bald eagle
became endangered because of
accumulation of DDT in eagles caused
them to lay eggs with very thin shells
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12.1 Ecology can be studied at many levels
• Ecologists work
at levels ranging
from individual
organisms to the
planet.
• It is convenient to
divide ecology into
five increasingly
comprehensive
levels.
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Organismal
ecology
Population
ecology
Community
ecology
Ecosystem
ecology
Global
ecology
12.1 Organismal ecology
1. Organismal
ecology focuses
on the ways that
organisms adapt to
their environments
through physiology
and behavior.
What type of questions
might an organismal
ecologist ask?
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An organism is an
individual living being.
12.1 Population ecology
2. Population
ecology is
concerned with
the factors that
affect population
size, growth,
and density.
What type of
questions might a
population ecologist
ask?
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A population is a group
of individuals of the same
species living in the same
place at the same time.
12.1 Community ecology
3. Questions in
community
ecology focus
on interactions
among species.
What type of
questions might a
community ecologist
ask?
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A community consists
of all the populations (of
multiple species) living
in a particular place.
12.1 Ecosystem ecology
4. Ecosystem
ecology is
concerned with
questions of
energy flow and
chemical cycling.
What type of
questions might an
ecosystem ecologist
ask?
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An ecosystem is all the
life living in a particular
area together with all the
nonliving components.
12.1 Ecology of the biosphere
5. At a global scale,
ecologists can study
the influence of
energy and matter
on organisms across
the biosphere.
What type of questions
might an ecologist ask
about the biosphere?
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The biosphere is the
global ecosystem.
12.2 The biosphere includes biotic and
abiotic factors
• The living organisms of an ecosystem
constitute its biotic factors.
• The abiotic factors of an ecosystem
are its nonliving components.
Abiotic factors can
have a profound effect
on the life within an
ecosystem.
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12.2 Examples of abiotic factors include the
supply of energy and nutrients
• The most important
abiotic factor is energy.
– Most ecosystems on
Earth are powered by
solar energy via sunlight.
• The availability of
inorganic nutrients can
impact plant growth.
– Examples are nitrogen
and phosphorous.
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12.2 Other important abiotic factors
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Wind
Water availability
Temperature
Fire
12.3 Opening Questions: How do abiotic
factors shape ecosystems?
• How do rainforests differ from deserts
in their abiotic factors?
• How might those differences result in
different biological communities?
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12.3 Energy flows through ecosystems
• Primary producers convert solar energy
to chemical energy via photosynthesis.
• Primary consumers
are herbivores that eat primary producers.
• Secondary consumers are carnivores that eat
primary consumers.
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12.3 Energy flows through ecosystems
• Tertiary consumers are
top-level predators.
– As trophic levels increase,
less energy is available at
each transfer.
• Decomposers are
organisms that break down
nonliving matter.
– Death at any level sends
energy to the decomposers.
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12.3 The trophic structure of an ecosystem
describes the feeding relationships
Energy enters an
ecosystem as
sunlight.
TROPHIC LEVEL 4
Tertiary consumers
TROPHIC LEVEL 3
Secondary consumers
TROPHIC LEVEL 2
Primary consumers
TROPHIC LEVEL 1
Primary producers
Decomposers break
down nonliving matter.
At each energy conversion heat is released.
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12.3 Different ecosystems have different
rates of primary production
• Biomass is the total amount of living material
in an ecosystem.
• Primary production
is a measure of the rate at which solar energy
is converted to biomass.
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12.3 As energy is passed from one trophic
level to the next, most of it is lost as heat
• From one trophic level
to the next, only around
10% of the energy
transfers.
• The cumulative loss of
energy means that each
level of trophic structure
can support fewer
organisms than the last.
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12.3 Energy availability can be visualized in
an ecological pyramid
Secondary
Consumers
Primary
Consumers
Producers
20,000,000 calories of primary production can support 10 vegetarians
or one meat-eater for one day.
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12.4 Elements cycle through the biosphere
• Energy flows through ecosystems.
• Chemical elements, such as carbon and
nitrogen, cycle through the biosphere.
• Elements move from abiotic (nonliving)
reservoirs such as the air, soil, and water, to
biotic (living) components of ecosystems in a
biogeochemical cycle.
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12.4 Biogeochemical cycles occur both
locally and globally
Abiotic reservoirs
Biotic components
− Includes the atmosphere,
rocks, and oceans
− Includes producers, consumers,
and decomposers
Geological processes
contribute to the abiotic
reservoirs.
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12.4 The carbon cycle is an example of a
biogeochemical cycle
The carbon cycle is affected by human activities (shown in red), primarily
the burning of fossil fuels, which releases trapped carbon into the
atmosphere as CO2.
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12.4 The nitrogen cycle is an example of a
biogeochemical cycle
Nitrogen is only available to living things after soil bacteria convert N2 to
compounds that plants can take up. Human effects on the nitrogen cycle
are shown in red.
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12.5 Opening Questions: Does energy flow
or cycle?
• Explain why in ecosystems energy flows
rather than being recycled.
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12.5 All water on Earth is interconnected
in a global water cycle
• A global water cycle connects ecosystems.
• Precipitation transfers water from the
atmosphere to the land.
• Conversely, evaporation from bodies of water
and transpiration from plants move water from
terrestrial sources to the atmosphere.
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12.5 The global water cycle
Over the oceans, the overall net movement of water is from the sea into
the atmosphere. Over land, the net movement is from the clouds down
to the land.
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12.6 Ecologists categorize the Earth’s
surface into a series of biomes
• A biome is a type of ecological community that
occupies a particular zone.
• Aquatic biomes cover much of the Earth’s surface and
are defined primarily by salinity.
• Terrestrial biomes
are identified primarily by the types of vegetation found
within them.
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12.6 Freshwater biomes
• Freshwater biomes generally have salt
concentrations of less than 1%.
• Freshwater biomes include:
Lakes and ponds
Rivers and streams
Wetlands
Freshwater biomes cover less than 1% of the Earth’s
surface, but are home to nearly 6% of all species.
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12.6 Marine biomes
• Marine biomes generally have water that is
about 3% salt by weight.
• Marine biomes include:
The pelagic realm,
which has photic and
aphotic zones
Coral reefs
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Hydrothermal
vents
12.6 Intermediate aquatic biomes
• Where land and freshwater biomes meet the
ocean, unique intermediate biomes are formed.
• These include:
Intertidal zones
Estuaries
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12.7 There are a variety of terrestrial biomes
• The distribution of terrestrial biomes depends
largely on two measures of climate: temperature
and rainfall.
• Each biome is characterized by differences in
temperature, rainfall, and the prevalence of
wildfires, and each has a dominant form of
vegetation.
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12.7 Some biomes are colder and drier
Polar ice is found in the
northernmost and
southernmost parts of
the Earth.
Tundra is
characterized by
dryness, bitter cold
temperatures, high
winds, and permafrost.
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12.7 Forest biomes vary by latitude
Coniferous forests
are dominated by
cone-bearing
evergreens.
Temperate broadleaf
forests occur in regions
of hot summers, cold
winters, and relatively
frequent rain.
Tropical forests
occur in wet, warm
climates near the
equator.
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12.7 Terrestrial biomes
Temperate grasslands
are found in regions with
cold winters, low rainfall,
and periodic drought.
Chaparral is found in
coastal areas where
ocean currents produce
mild, rainy winters
and hot, dry summers
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12.7 More terrestrial biomes
Savannas are warm,
fairly dry climates that
primarily contain grasses
with scattered trees.
Deserts have very low
rainfall. There are both
hot and cold deserts.
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12.8 Changes in niches with increase in
altitudes
As you climb up a mountain, the vegetation
changes with altitude. List some factors that
may be causing this change.
If you started at sea level near the
equator, what vegetation types might
you see as you hike to the top?
List some factors that may be causing
this vegetation change.
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12.8 Interactions between species play
important roles in communities
• Within a community, species interact with
members as they compete for food, water,
sunlight, or living space.
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12.8 Competition is mutually harmful
• Competition may occur when two or more
species in a community rely on similar limiting
resources.
• According to the competitive exclusion
principle, if the resources required by two
species are too similar, they cannot coexist.
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12.8 Mutualism is beneficial to both species
• Mutualism is a form of interspecies
interaction in which both species benefit.
– It often occurs among species that are
symbiotic, living in close physical association
with one another, but not all symbiotic
relationships are mutual.
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12.8 Some interactions are beneficial to one
species and harmful to the other
• Predation is an interaction in which
a predator species kills and eats a prey
species.
• Herbivory is the eating of plant parts
by an animal.
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12.8 Some interactions are beneficial to
one species and harmful to the other
• A parasite lives on or
in (but does not kill) a
host, from which it
obtains nutrients.
• Pathogens are
disease-causing
microorganisms.
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12.9 Opening Questions: What happens
when species compete?
• Imagine that two species of related birds
live in the same habitat and eat similar
food items.
• Design a simple experiment to test the
competitive exclusion hypothesis.
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12.9 Food webs describe multiple trophic
structures
• Trophic structure
describes the feeding
relationships within a
community.
• Food chains and food
webs describe
the transfer of organic
material from one
trophic level to the next.
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12.9 A food chain is a simplified description
of one part of the trophic structure
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12.9 A food web interconnects multiple
food chains
A food web of a
hypothetical
forest community
Arrows indicate
energy transfer or
“who eats whom.”
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12.9 Toxins can accumulate in higher levels
• Biological magnification is the tendency of
toxins to become concentrated as they pass
through a food chain.
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12.10 Opening Questions: Which forest is
more diverse?
Consider these two forests.
Which forest has higher species diversity and why?
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12.10 Species diversity includes both
species richness and abundance
• Both forests have the same number of species, or species richness.
However, the fraction accounted for by each species, or relative
abundance, differs between the two communities.
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12.10 Keystone species can drive diversity
• A keystone species is a species that has a
disproportionately large effect on its environment
relative to its abundance.
• Ecologists studying the Alaskan coast
discovered that decline in the sea otter
populations allowed sea urchins
to quickly multiply.
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12.10 Communities are rarely static
• Primary succession occurs when an area has
been rendered virtually lifeless with no soil.
Disturbance
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12.10 Communities are rarely static
• Secondary succession occurs after a
disturbance that kills much of the life in an area
but leaves the soil intact.
• After a disturbance, an area will be reoccupied
by a series of species. Ecological succession
may take hundreds or thousands of years.
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12.11 Opening Questions: No tuna fish
sandwiches if you are pregnant?
Pregnant women are advised to limit their
consumption of large predatory fish, such as
swordfish and tuna, to once per week. These fish
may have high levels of mercury stored in their
tissues and eating them may damage a developing
fetus. For other smaller fish, such as sardines,
there are no limitations.
Why might different fish species have such
variation in the mercury content of their
tissues? Explain.
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12.11 Invasive species disrupt ecosystems
• When non-native organisms are introduced
to a community, they can spread rapidly,
becoming an invasive species.
• Invasive species are now a leading cause
of extinctions of local populations.
Lionfish were introduced
into the Caribbean and
consumed other fish
voraciously.
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12.11 A rogue’s gallery of invasive species
Burmese pythons were set loose in
Florida.
Kudzu is a climbing vine,
introduced to the southern U.S.
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12.11 Controlling invasive species
• Ecologists may implement
biological control, the
intentional release of a
natural enemy.
• Biological control species
must be closely studied.
– Mongooses were introduced
to Hawaii to eat rats, but are
such good hunters that they
also decimated native birds.
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12.11 Modern agriculture presents unique
challenges of biological control
• Integrated pest management is a
method that utilizes several strategies:
– Biological control, pest-resistant crop
varieties, judicious use of chemicals, release
of sterile pests, and other biological and
behavioral changes.
Integrated pest management
has been used effectively for
cotton crops in India.
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12.12 Opening Questions: Do you know any
invasive species?
• Every state now has at least a few
notorious invasive species.
• http://mdc.mo.gov/discover-nature/fieldguide/invasive-species/invasive-speciesfield-guide
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12.12 Ecologists measure biodiversity on
many levels
• Biodiversity is a general term for the
variety of living things on Earth.
• Biodiversity includes:
– Genetic diversity (within a population)
– Species diversity
– Ecological diversity
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12.12 Genetic biodiversity refers to the
collection of genes within a population
• Severely reducing genetic
variation makes the
population less able to
adapt to a changing
environment.
– Because virtually all the
potatoes in the country
were genetically
identical,
the Irish potato blight
caused crop failure
and famine.
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12.12 Species biodiversity refers to the
number of different species
• Extinction is the irreversible loss of all
populations of a species.
• Ecologists estimate that at the current rate
half of all living plant and animal species
will be extinct by the end of this century.
The last Carolina parakeet
died in a zoo in 1918.
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12.12 Ecosystem biodiversity refers to the
variety of ecosystems found on Earth
• The degradation of ecosystems threatens
ecosystem services, benefits that
ecosystems provide to people such as:
– Waste decomposition
– Water cycling
– Nutrient cycling
– Food production
– Recreation
A tropical reef damaged
by a drag net
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12.12 Causes of biodiversity loss
• Habitat destruction
is the single greatest
threat to biodiversity.
– This includes
destruction of habitat
due to development,
agriculture, forestry,
mining, and dam
construction.
Brazilian rainforest being
cleared for agricultural use
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12.12 Causes of biodiversity loss
• Invasive species are an increasingly
grave threat to biodiversity.
– The invader may have no natural predators
and can thus multiply unchecked, causing the
extinction of competitors or prey species.
Introduced to Guam,
brown tree snakes
have driven several
bird species to
extinction or near
extinction.
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12.12 Causes of biodiversity loss
• Overharvesting species faster than they
can naturally replenish leads to a loss of
biodiversity.
– This includes hunting, fishing, and logging.
Overfishing has
decimated the
populations of
many wild fish.
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12.12 Causes of biodiversity loss
• Pollution of the air and water contributes
to biodiversity loss at the local, regional,
and global levels.
The Deepwater Horizon
oil rig explosion in 2010
released oil into the Gulf
of Mexico.
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12.12 Causes of biodiversity loss
• Global climate change impacts
biodiversity at both local and global scales.
– Ecologists predict declining biodiversity due to
changes in rainfall patterns, disruption of
seasonal patterns, rising temperatures, and
ocean acidification.
Coral bleaching is a
phenomenon that has
been linked with the
increase in water
temperatures.
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12.13 Populations vary in density,
dispersion, and survivorship curves
• Ecologists study populations in terms of their
density, dispersion patterns, survivorship curves,
and life histories.
• Collecting such data can provide insights
into the dynamics of a population in its ecosystem.
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12.13 Age structure is the number of
individuals in different age groups
• Comparing age structures of human populations
can provide insights into social conditions.
Which country will need more high
schools in the future? Explain.
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12.13 Survivorship curves graph the
percentage of individuals alive over time
• Survivorship is the chance that an
individual member of a given population
will live to a particular age.
How do the curves vary among the three species?
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12.13 Population density and dispersion are
important measurements
• Population density is the number of
members of a species per unit area or
volume of the habitat.
• Dispersion patterns are the way
individuals are spaced within a habitat.
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12.14 Growth models can predict changes
in population size
• In its simplest terms, population size is
calculated from the number of births minus the
number of deaths.
• Ecologists have developed idealized models to
help us better understand
changes in population size.
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12.14 Exponential population growth
• Imagine a population where there are no
predators, no disease, and plenty of food.
• Over time, what do you expect will happen
to population size?
Exponential growth
occurs when the
population size of
each new generation
is a multiple of the
previous generation.
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12.14 The exponential growth model
Exponential growth requires unlimited resources.
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12.14 Most populations cannot sustain
exponential growth indefinitely
• In real-world populations,
there are limiting factors,
environmental constraints
that put a cap on the size of
a population.
• The carrying capacity is
the maximum population
size that can survive in an
environment.
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12.14 The logistic growth model
• What happens if there are limiting factors?
– Predators, disease, food shortages
• Over time, what do you expect will happen
to population size?
Logistic growth is
where the size of a
population grows
rapidly until it nears
its carrying capacity
for that environment.
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12.14 The logistic growth model
Logistic growth includes limiting factors.
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12.14 Limiting factors include two broad
categories
• Density-dependent factors are limiting
factors whose influence is affected by population density.
– Competition, disease
• Density-independent factors are unrelated
to population density.
– Weather, environmental disturbance
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12.15 Human population growth is
exponential
• Unlike nearly every natural population,
humans have demonstrated exponential
growth, especially over the last 250 years.
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12.15 The human population growth curve
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12.15 Population age structure can inform
future population size
• Current population growth is affected by the birth
rate 15 to 30 years ago, since that is when
today’s child-bearers were born.
Age structure
can be used to
project future
population
size.
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12.16 Opening Questions: What impact
does our population have on other
species?
The global human population is now over 7
billion and still growing.
How might the increasing human population
impact other species populations?
Explain using ecological concepts.
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12.16 Humans affect many ecosystems
• Humans depend on the continued health of
Earth’s ecosystems for our own survival, but we
threaten the health of ecosystems in several
ways.
• No part of the biosphere remains unchanged by
the collective influence of over 7 billion humans.
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12.16 Ecological footprints reflect our
resource usage
• An ecological footprint is an estimate of
the amount of land and water required to
sustain one person.
Is it possible for everyone to have the
same footprint as a U.S. average?
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12.16 Human impact: Forest destruction
• The primary cause of forest destruction is
clearing for agriculture.
Satellite images for one region
of a South American rainforest
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12.16 Human impact: Freshwater shortages
• Some regions of the world are already
experiencing dire freshwater shortages,
and the problem will probably get worse in
the near future.
Polluted creek in Orange
County, California
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Depleted water levels at
Arrowrock Dam, Idaho
12.16 Human impact: Declining species
• Endangered species are those with rapidly
declining populations.
An endangered hawksbill
turtle with researcher
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The Canada lynx is considered
a threatened species.
12.17 Humans can work together to solve
ecological problems
• Conservation biology is a branch of ecology
that seeks to investigate and reverse the loss of
biodiversity.
• The field of restoration ecology uses ecological
principles to help repair degraded areas.
Conservation and restoration ecology are both
expanding fields and are making significant progress.
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12.17 Identifying biodiversity hot spots
• Biodiversity hot spots are relatively small
areas with unusually high concentrations of
endemic species and endangered species.
Endemic species
are only found in
a relatively small
geographic area.
The ring-tailed lemur is endemic
to the island of Madagascar.
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12.17 Conservation biologists recommend
preserving habitat in biodiversity hot spots
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12.17 When people are motivated to act,
species recovery can be dramatic
• Bald eagles declined dramatically in the lower
48 U.S. states due to habitat loss and
environmental toxins, primarily DDT.
• Today, bald eagles have recovered to over
10,000 breeding pairs.
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12.17 Conservation biologists also aim to
maintain ecosystem biodiversity
• Fragmentation is the splitting of habitats
that causes populations to become
isolated from each other.
• One remedy involves maintaining corridors
to connect habitat
patches.
A bridge in Banff, Canada,
allows animals to
access areas otherwise
separated by a road.
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12.17 Restoration ecologists work to repair
degraded habitats
• This includes returning
native species and
bioremediation, the
use of living organisms
to detoxify polluted
ecosystems.
Workers plant sunflowers
to naturally remove toxins
from topsoil.
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12.17 Promoting sustainable development
• The goal of sustainable development is
to maintain the productivity of Earth’s
ecosystems indefinitely.
– Sensible, science-driven policies can help us
take corrective action now, while much hope
remains.
Education plays an
important role in
conserving our
biosphere.
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12.18 Opening Questions: What are some
solutions?
Sustainable development aims to maintain
ecological process and ecosystems, while
also providing for human needs.
Imagine your state in 50 years. What
steps could we take today to both make
your state ecologically healthy and
provide for human needs (social,
cultural, and economic)?
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12.18 The accumulation of greenhouse
gases is causing global climate change
• Greenhouse gases are airborne chemicals that capture
and hold heat within Earth’s atmosphere.
• They include:
– Carbon dioxide (CO2) Methane (CH4), Nitrous oxide
(N2O), Water (H2O) vapor
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12.18 Global climate change: The data
• Since 1880, global surface temperatures have
increased.
• Atmospheric greenhouse gas levels are higher
now than at any time in the past 800,000 years.
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12.18 Carbon dioxide is an important player
• The human activities that contribute the
most CO2 to the atmosphere are power
generation and industry.
CO2 contribution from
various human activities
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12.18 Greenhouse gases act as an
atmospheric blanket, trapping heat
• The greenhouse effect is vital to life on
Earth; without it, most of Earth’s surface
would be too cold to support life.
• The more greenhouse gases there are
the more heat is trapped.
The consensus among scientists is that the
atmospheric accumulation of human-made
greenhouse gases is gradually warming the
Earth, causing global climate change.
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12.18 The greenhouse effect
Solar energy enters Earth’s
atmosphere as sunlight.
Much of this solar
energy is reflected
back into the atmosphere
as heat energy.
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Some of the heat energy
escapes into space.
Some heat is reflected
back downward by
greenhouse gases in the
atmosphere.
12.18 Global climate change has many
far-reaching effects on ecosystems
Ecosystem effects include:
– With rising temperatures, the ranges of many
species are shifting toward the poles or to
higher elevations.
– Polar habitats are melting away.
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12.18 Ecosystems effects impact human life
Ecosystem effects include:
– Warming oceans cause coral to lose their
symbiotic algae. Coral death can mean the
loss of entire reef ecosystems.
– Earlier snow melt results in dry conditions and
an increase in devastating wildfires.
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12.19 Opening Questions: Where is all that
CO2 coming from?
One of the most common anthropogenic
(made by humans) greenhouse gases is CO2.
Why does burning fossil fuels generate
CO2 emissions?
How is burning fossil fuels like cellular
respiration?
How were fossil fuels made?
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12.19 Organisms adapt to their environments
• The fields of ecology and evolutionary
biology are intertwined.
• Populations evolve in response to both
living (biotic) factors, such as predators,
as well as nonliving (abiotic) factors,
such as temperature and rainfall.
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12.19 Possible adaptations fall into three
broad categories
• Organisms adapt to environmental
conditions in a variety of ways:
– Physiological responses
– Anatomical responses
– Behavioral responses
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12.19 Physiological responses
• Many organisms respond to changing conditions
by changing their physiology, the functioning of
body components.
Goose bumps in response to cold
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Increasing red blood cells through
high-elevation acclimation
12.19 Anatomical responses
• In response to changing environments,
organisms may change their anatomy, adjusting
body shape or structure.
Plants orient themselves
toward a source of light.
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Many mammals grow
seasonal heavy coats.
12.19 Behavioral responses
• Many animals respond to changes in the
environment by altering their behavior.
As humans, we change our
clothing.
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Migration is a response changing
environmental conditions.