Download AP UNIT 9

Chapter 51
Animal Behavior
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Biology
Eighth Edition
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Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp
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Concept 51.1: Discrete sensory inputs can
stimulate both simple and complex behaviors
• An animal’s behavior is its response to external
and internal stimuli
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• Proximate causation, or “how” explanations,
focus on
– Environmental stimuli that trigger a behavior
– Genetic, physiological, and anatomical
mechanisms underlying a behavior
• Ultimate causation, or “why” explanations,
focus on
– Evolutionary significance of a behavior
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• Behavioral ecology is the study of the
ecological and evolutionary basis for animal
behavior
• It integrates proximate and ultimate
explanations for animal behavior
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Fixed Action Patterns
• A fixed action pattern is a sequence of
unlearned, innate behaviors that is
unchangeable
• Once initiated, it is usually carried to
completion
• A fixed action pattern is triggered by an
external cue known as a sign stimulus
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• In male stickleback fish, the stimulus for attack
behavior is the red underside of an intruder
• When presented with unrealistic models, as
long as some red is present, the attack
behavior occurs
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Fig. 51-3
(a)
(b)
Oriented Movement
• Environmental cues can trigger movement in a
particular direction
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Kinesis and Taxis
• A kinesis is a simple change in activity or
turning rate in response to a stimulus
• For example, sow bugs become more active in
dry areas and less active in humid areas
• Though sow bug behavior varies with humidity,
sow bugs do not move toward or away from
specific moisture levels
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Fig. 51-4
Dry open
area
Sow
bug
Moist site
under leaf
• A taxis is a more or less automatic, oriented
movement toward or away from a stimulus
• Many stream fish exhibit a positive taxis and
automatically swim in an upstream direction
• This taxis prevents them from being swept
away and keeps them facing the direction from
which food will come
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Migration
• Migration is a regular, long-distance change in
location
• Animals can orient themselves using
– The position of the sun and their circadian
clock, an internal 24-hour clock that is an
integral part of their nervous system
– The position of the North Star
– The Earth’s magnetic field
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Animal Signals and Communication
• In behavioral ecology, a signal is a behavior
that causes a change in another animal’s
behavior
• Communication is the transmission and
reception of signals
• Animals communicate using visual, chemical,
tactile, and auditory signals
• The type of signal is closely related to lifestyle
and environment
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• Honeybees show complex communication with
symbolic language
• A bee returning from the field performs a dance
to communicate information about the position
of a food source
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Fig. 51-8
(a) Worker bees
(b) Round dance
(food near)
(c) Waggle dance
(food distant)
A
30°
C
B
Location A
Beehive
Location B
Location C
Pheromones
• Many animals that communicate through odors
emit chemical substances called pheromones
• Pheromones are effective at very low
concentrations
• When a minnow or catfish is injured, an alarm
substance in the fish’s skin disperses in the
water, inducing a fright response among fish in
the area
• Many insects also use pheromones
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Fig. 51-9
(a) Minnows
before
alarm
(b) Minnows
after
alarm
Concept 51.2: Learning establishes specific links
between experience and behavior
• Innate behavior is developmentally fixed and
under strong genetic influence. It is inherited.
• Learning is the modification of behavior based
on specific experiences
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Habituation
• Habituation is a simple form of learning that
involves loss of responsiveness to stimuli that
convey little or no information
– For example, birds will stop responding to
alarm calls from their species if these are not
followed by an actual attack
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Imprinting
• Imprinting is a behavior that includes learning
and innate components and is generally
irreversible
• It is distinguished from other learning by a
sensitive period
• A sensitive period is a limited developmental
phase that is the only time when certain
behaviors can be learned
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• An example of imprinting is young geese
following their mother
• Konrad Lorenz showed that when baby geese
spent the first few hours of their life with him,
they imprinted on him as their parent
Video: Ducklings
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• Conservation biologists have taken advantage
of imprinting in programs to save the whooping
crane from extinction
• Young whooping cranes can imprint on
humans in “crane suits” who then lead crane
migrations using ultralight aircraft
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Fig. 51-10
(a) Konrad Lorenz and geese
(b) Pilot and cranes
Spatial Learning
• Spatial learning is a more complex
modification of behavior based on experience
with the spatial structure of the environment
• Niko Tinbergen showed how digger wasps use
landmarks to find nest entrances
Video: Bee Pollinating
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Fig. 51-11
EXPERIMENT
Nest
Pinecone
RESULTS
Nest
No nest
Associative Learning
• In associative learning, animals associate
one feature of their environment with another
– For example, a white-footed mouse will avoid
eating caterpillars with specific colors after a
bad experience with a distasteful monarch
butterfly caterpillar
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• Classical conditioning is a type of associative
learning in which an arbitrary stimulus is
associated with a reward or punishment
– For example, a dog that repeatedly hears a
bell before being fed will salivate in anticipation
at the bell’s sound
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• Operant conditioning is a type of associative
learning in which an animal learns to associate
one of its behaviors with a reward or
punishment
• It is also called trial-and-error learning
– For example, a rat that is fed after pushing a
lever will learn to push the lever in order to
receive food
– For example, a predator may learn to avoid a
specific type of prey associated with a painful
experience
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Fig. 51-12
Concept 51.4: Selection for individual survival and
reproductive success can explain most behaviors
• Genetic components of behavior evolve
through natural selection
• Behavior can affect fitness by influencing
foraging and mate choice
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Foraging Behavior
• Natural selection refines behaviors that
enhance the efficiency of feeding
• Foraging, or food-obtaining behavior, includes
recognizing, searching for, capturing, and
eating food items
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Evolution of Foraging Behavior
• In Drosophila melanogaster, variation in a gene
dictates foraging behavior in the larvae
• Larvae with one allele travel farther while
foraging than larvae with the other allele
• Larvae in high-density populations benefit from
foraging farther for food, while larvae in lowdensity populations benefit from short-distance
foraging
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• Natural selection favors different foraging
behavior depending on the density of the
population
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Optimal Foraging Model
• Optimal foraging model views foraging
behavior as a compromise between benefits of
nutrition and costs of obtaining food
• The costs of obtaining food include energy
expenditure and the risk of being eaten while
foraging
• Natural selection should favor foraging
behavior that minimizes the costs and
maximizes the benefits
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• Optimal foraging behavior is demonstrated by
the Northwestern crow
• A crow will drop a whelk (a mollusc) from a
height to break its shell and feed on the soft
parts
• The crow faces a trade-off between the height
from which it drops the whelk and the number of
times it must drop the whelk
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• Researchers determined experimentally that the
total flight height (which reflects total energy
expenditure) was minimized at a drop height of
5m
• The average flight height for crows is 5.2 m
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Mating Behavior and Mate Choice
• Mating behavior includes seeking or attracting
mates, choosing among potential mates, and
competing for mates
• Mating behavior results from a type of natural
selection called sexual selection
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Mating Systems and Parental Care
• The mating relationship between males and
females varies greatly from species to species
• In many species, mating is promiscuous, with
no strong pair-bonds or lasting relationships
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• Needs of the young are an important factor
constraining evolution of mating systems
• Consider bird species where chicks need a
continuous supply of food
– A male maximizes his reproductive success by
staying with his mate, and caring for his chicks
(monogamy)
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• Consider bird species where chicks are soon
able to feed and care for themselves
– A male maximizes his reproductive success by
seeking additional mates (polygyny)
• Females can be certain that eggs laid or young
born contain her genes; however, paternal
certainty depends on mating behavior
• Certainty of paternity influences parental care
and mating behavior
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• Paternal certainty is relatively low in species
with internal fertilization because mating and
birth are separated over time
• Certainty of paternity is much higher when egg
laying and mating occur together, as in external
fertilization
• In species with external fertilization, parental
care is at least as likely to be by males as by
females
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Chapter 52
An Introduction to Ecology
and the Biosphere
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Biology
Eighth Edition
Neil Campbell and Jane Reece
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Overview: The Scope of Ecology
• Ecology is the scientific study of the
interactions between organisms and the
environment
• These interactions determine distribution of
organisms and their abundance
• Ecology reveals the richness of the biosphere
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• A population is a group of individuals of the
same species living in an area
• Population ecology focuses on factors
affecting how many individuals of a species live
in an area
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• A community is a group of populations of
different species in an area
• Community ecology deals with the whole
array of interacting species in a community
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• An ecosystem is the community of organisms
in an area and the physical factors with which
they interact
• Ecosystem ecology emphasizes energy flow
and chemical cycling among the various biotic
and abiotic components
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• The biosphere is the global ecosystem, the
sum of all the planet’s ecosystems
• Global ecology examines the influence of
energy and materials on organisms across the
biosphere
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Ecology and Environmental Issues
• Ecology provides the scientific understanding
that underlies environmental issues
• Ecologists make a distinction between science
and advocacy
• Rachel Carson is credited with starting the
modern environmental movement with the
publication of Silent Spring in 1962
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Concept 52.2: Interactions between organisms and
the environment limit the distribution of species
• Ecologists have long recognized global and
regional patterns of distribution of organisms
within the biosphere
• Biogeography is a good starting point for
understanding what limits geographic
distribution of species
• Ecologists recognize two kinds of factors that
determine distribution: biotic, or living factors,
and abiotic, or nonliving factors
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• Ecologists consider multiple factors when
attempting to explain the distribution of species
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Fig. 52-6
Why is species X absent
from an area?
Yes
Does dispersal
limit its
distribution?
No
Area inaccessible
or insufficient time
Does behavior
limit its
distribution?
Yes
Habitat selection
Yes
No
Do biotic factors
(other species)
limit its
distribution?
No
Predation, parasitism, Chemical
competition, disease factors
Do abiotic factors
limit its
distribution?
Water
Oxygen
Salinity
pH
Soil nutrients, etc.
Temperature
Physical Light
factors Soil structure
Fire
Moisture, etc.
Dispersal and Distribution
• Dispersal is movement of individuals away
from centers of high population density or from
their area of origin
• Dispersal contributes to global distribution of
organisms
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Biotic Factors
• Biotic factors that affect the distribution of
organisms may include:
– Interactions with other species
– Predation
– Competition
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Abiotic Factors
• Abiotic factors affecting distribution of
organisms include:
– Temperature
– Water
– Sunlight
– Wind
– Rocks and soil
• Most abiotic factors vary in space and time
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Temperature
• Environmental temperature is an important
factor in distribution of organisms because of
its effects on biological processes
• Cells may freeze and rupture below 0°C, while
most proteins denature above 45°C
• Mammals and birds expend energy to regulate
their internal temperature
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Water
• Water availability in habitats is another
important factor in species distribution
• Desert organisms exhibit adaptations for water
conservation
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Salinity
• Salt concentration affects water balance of
organisms through osmosis
• Few terrestrial organisms are adapted to highsalinity habitats
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Sunlight
• Light intensity and quality affect photosynthesis
• Water absorbs light, thus in aquatic
environments most photosynthesis occurs near
the surface
• In deserts, high light levels increase
temperature and can stress plants and animals
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Rocks and Soil
• Many characteristics of soil limit distribution of
plants and thus the animals that feed upon
them:
– Physical structure
– pH
– Mineral composition
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Climate
• Four major abiotic components of climate are
temperature, water, sunlight, and wind
• The long-term prevailing weather conditions in
an area constitute its climate
• Macroclimate consists of patterns on the
global, regional, and local level
• Microclimate consists of very fine patterns,
such as those encountered by the community
of organisms underneath a fallen log
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Global Climate Patterns
• Global climate patterns are determined largely
by solar energy and the planet’s movement in
space
• Sunlight intensity plays a major part in
determining the Earth’s climate patterns
• More heat and light per unit of surface area
reach the tropics than the high latitudes
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Concept 52.3: Aquatic biomes are diverse and
dynamic systems that cover most of Earth
• Biomes are the major ecological associations
that occupy broad geographic regions of land
or water
• Varying combinations of biotic and abiotic
factors determine the nature of biomes
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• Aquatic biomes account for the largest part of
the biosphere in terms of area
• They can contain fresh water or salt water
(marine)
• Oceans cover about 75% of Earth’s surface
and have an enormous impact on the
biosphere
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Aquatic Biomes
• Major aquatic biomes can be characterized by
their physical environment, chemical
environment, geological features,
photosynthetic organisms, and heterotrophs
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Concept 52.4: The structure and distribution of
terrestrial biomes are controlled by climate and
disturbance
• Climate is very important in determining why
terrestrial biomes are found in certain areas
• Biome patterns can be modified by
disturbance such as a storm, fire, or human
activity
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Fig. 52-19
Tropical forest
Savanna
Desert
30ºN
Tropic of
Cancer
Equator
Tropic of
Capricorn
30ºS
Chaparral
Temperate
grassland
Temperate
broadleaf forest
Northern
coniferous forest
Tundra
High mountains
Polar ice
Climate and Terrestrial Biomes
• Climate has a great impact on the distribution
of organisms
• This can be illustrated with a climograph, a
plot of the temperature and precipitation in a
region
• Biomes are affected not just by average
temperature and precipitation, but also by the
pattern of temperature and precipitation
through the year
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Terrestrial Biomes
• Terrestrial biomes can be characterized by
distribution, precipitation, temperature, plants,
and animals
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Chapter 53
Population Ecology
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Eighth Edition
Neil Campbell and Jane Reece
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Concept 53.1: Dynamic biological processes
influence population density, dispersion, and
demographics
• A population is a group of individuals of a
single species living in the same general area
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Density and Dispersion
• Density is the number of individuals per unit
area or volume
• Dispersion is the pattern of spacing among
individuals within the boundaries of the
population
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Density: A Dynamic Perspective
• In most cases, it is impractical or impossible to
count all individuals in a population
• Sampling techniques can be used to estimate
densities and total population sizes
• Population size can be estimated by either
extrapolation from small samples, an index of
population size, or the mark-recapture
method
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• Density is the result of an interplay between
processes that add individuals to a population
and those that remove individuals
• Immigration is the influx of new individuals
from other areas
• Emigration is the movement of individuals out
of a population
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Patterns of Dispersion
• Environmental and social factors influence
spacing of individuals in a population
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Fig. 53-4
(a) Clumped
(b) Uniform
(c) Random
Demographics
• Demography is the study of the vital statistics
of a population and how they change over time
• Death rates and birth rates are of particular
interest to demographers
• A life table is an age-specific summary of the
survival pattern of a population
• It is best made by following the fate of a
cohort, a group of individuals of the same age
• A survivorship curve is a graphic way of
representing the data in a life table
Number of survivors (log scale)
Fig. 53-6
1,000
I
100
II
10
III
1
0
50
Percentage of maximum life span
100
Concept 53.2: Life history traits are products of
natural selection
• An organism’s life history comprises the traits
that affect its schedule of reproduction and
survival:
– The age at which reproduction begins
– How often the organism reproduces
– How many offspring are produced during each
reproductive cycle
• Life history traits are evolutionary outcomes
reflected in the development, physiology, and
behavior of an organism
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Evolution and Life History Diversity
• Life histories are very diverse
• Species that exhibit semelparity, or big-bang
reproduction, reproduce once and die
• Species that exhibit iteroparity, or repeated
reproduction, produce offspring repeatedly
• Highly variable or unpredictable environments
likely favor big-bang reproduction, while
dependable environments may favor repeated
reproduction
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Fig. 53-7
“Trade-offs” and Life Histories
• Organisms have finite resources, which may
lead to trade-offs between survival and
reproduction
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• Some plants produce a large number of small
seeds, ensuring that at least some of them will
grow and eventually reproduce
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Fig. 53-9a
(a) Dandelion
• Other types of plants produce a moderate
number of large seeds that provide a large
store of energy that will help seedlings become
established
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Fig. 53-9b
(b) Coconut palm
• In animals, parental care of smaller broods
may facilitate survival of offspring
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Fig. 53-8
Parents surviving the following winter (%)
RESULTS
100
Male
Female
80
60
40
20
0
Reduced
brood size
Normal
brood size
Enlarged
brood size
Concept 53.3: The exponential model describes
population growth in an idealized, unlimited
environment
• It is useful to study population growth in an
idealized situation
• Idealized situations help us understand the
capacity of species to increase and the
conditions that may facilitate this growth
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Per Capita Rate of Increase
• If immigration and emigration are ignored, a
population’s growth rate (per capita increase)
equals birth rate minus death rate
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• Zero population growth occurs when the birth
rate equals the death rate
• Most ecologists use differential calculus to
express population growth as growth rate at a
particular instant in time:
N 
t rN
where N = population size, t = time, and r = per
capita rate of increase = birth – death
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Exponential Growth
• Exponential population growth is population
increase under idealized conditions
• Under these conditions, the rate of
reproduction is at its maximum, called the
intrinsic rate of increase
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• Equation of exponential population growth:
dN 
rmaxN
dt
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• Exponential population growth results in a Jshaped curve
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Fig. 53-10
2,000
Population size (N)
dN
= 1.0N
dt
1,500
dN
= 0.5N
dt
1,000
500
0
0
5
10
Number of generations
15
• The J-shaped curve of exponential growth
characterizes some rebounding populations
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Fig. 53-11
Elephant population
8,000
6,000
4,000
2,000
0
1900
1920
1940
Year
1960
1980
Concept 53.4: The logistic model describes how a
population grows more slowly as it nears its
carrying capacity
• Exponential growth cannot be sustained for
long in any population
• A more realistic population model limits growth
by incorporating carrying capacity
• Carrying capacity (K) is the maximum
population size the environment can support
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The Logistic Growth Model
• In the logistic population growth model, the
per capita rate of increase declines as carrying
capacity is reached
• We construct the logistic model by starting with
the exponential model and adding an
expression that reduces per capita rate of
increase as N approaches K
(K  N)
dN
 rmax N
dt
K
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Table 53-3
• The logistic model of population growth
produces a sigmoid (S-shaped) curve
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Fig. 53-12
Exponential
growth
Population size (N)
2,000
dN
= 1.0N
dt
1,500
K = 1,500
Logistic growth
1,000
dN
= 1.0N
dt
1,500 – N
1,500
500
0
0
5
10
Number of generations
15
The Logistic Model and Real Populations
• The growth of laboratory populations of
paramecia fits an S-shaped curve
• These organisms are grown in a constant
environment lacking predators and competitors
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Number of Daphnia/50 mL
Number of Paramecium/mL
Fig. 53-13
1,000
800
600
400
200
0
180
150
120
90
60
30
0
0
5
10
Time (days)
15
(a) A Paramecium population in the lab
0
20
40
60
80 100 120
Time (days)
(b) A Daphnia population in the lab
140
160
Number of Paramecium/mL
Fig. 53-13a
1,000
800
600
400
200
0
0
5
10
Time (days)
15
(a) A Paramecium population in the lab
• Some populations overshoot K before settling
down to a relatively stable density
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Number of Daphnia/50 mL
Fig. 53-13b
180
150
120
90
60
30
0
0
20
40
60
80 100 120
Time (days)
(b) A Daphnia population in the lab
140
160
The Logistic Model and Life Histories
• Life history traits favored by natural selection
may vary with population density and
environmental conditions
• K-selection, or density-dependent selection,
selects for life history traits that are sensitive to
population density
• r-selection, or density-independent selection,
selects for life history traits that maximize
reproduction
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Concept 53.5: Many factors that regulate
population growth are density dependent
• There are two general questions about
regulation of population growth:
– What environmental factors stop a population
from growing indefinitely?
– Why do some populations show radical
fluctuations in size over time, while others
remain stable?
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Population Change and Population Density
• In density-independent populations, birth rate
and death rate do not change with population
density
• In density-dependent populations, birth rates
fall and death rates rise with population density
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Density-Dependent Population Regulation
• Density-dependent birth and death rates are an
example of negative feedback that regulates
population growth
• They are affected by many factors, such as
competition for resources, territoriality, disease,
predation, toxic wastes, and intrinsic factors
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Competition for Resources
• In crowded populations, increasing population
density intensifies competition for resources
and results in a lower birth rate
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Percentage of juveniles producing lambs
Fig. 53-16
100
80
60
40
20
0
200
300
400
500
Population size
600
Territoriality
• In many vertebrates and some invertebrates,
competition for territory may limit density
• Cheetahs are highly territorial, using chemical
communication to warn other cheetahs of their
boundaries
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Disease
• Population density can influence the health and
survival of organisms
• In dense populations, pathogens can spread
more rapidly
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Predation
• As a prey population builds up, predators may
feed preferentially on that species
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Toxic Wastes
• Accumulation of toxic wastes can contribute to
density-dependent regulation of population size
• Think of fish in a tank or animals in a cage. The
more there are the faster the wastes build up. If
wastes are not removed they will poison
themselves and many will die until there are
fewer creating less waste.
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Intrinsic Factors
• For some populations, intrinsic (physiological)
factors appear to regulate population size
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Population Dynamics
• The study of population dynamics focuses on
the complex interactions between biotic and
abiotic factors that cause variation in
population size
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Stability and Fluctuation
• Long-term population studies have challenged
the hypothesis that populations of large
mammals are relatively stable over time
• Weather can affect population size over time
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 53-18
2,100
Number of sheep
1,900
1,700
1,500
1,300
1,100
900
700
500
0
1955
1965
1975
1985
Year
1995
2005
• Changes in predation pressure can drive
population fluctuations
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Fig. 53-19
2,500
50
Moose
40
2,000
30
1,500
20
1,000
10
500
0
1955
1965
1975
1985
Year
1995
0
2005
Number of moose
Number of wolves
Wolves
Population Cycles: Scientific Inquiry
• Some populations undergo regular boom-andbust cycles
• Lynx populations follow the 10 year boom-andbust cycle of hare populations
• Three hypotheses have been proposed to
explain the hare’s 10-year interval
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 53-20
Snowshoe hare
120
9
Lynx
80
6
40
3
0
0
1850
1875
1900
Year
1925
Number of lynx
(thousands)
Number of hares
(thousands)
160
• Hypothesis: The hare’s population cycle follows
a cycle of winter food supply
• If this hypothesis is correct, then the cycles
should stop if the food supply is increased
• Additional food was provided experimentally to
a hare population, and the whole population
increased in size but continued to cycle
• No hares appeared to have died of starvation
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• Hypothesis: The hare’s population cycle is
driven by pressure from other predators
• In a study conducted by field ecologists, 90%
of the hares were killed by predators
• These data support this second hypothesis
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
• Hypothesis: The hare’s population cycle is
linked to sunspot cycles
• Sunspot activity affects light quality, which in
turn affects the quality of the hares’ food
• There is good correlation between sunspot
activity and hare population size
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
• The results of all these experiments suggest
that both predation and sunspot activity
regulate hare numbers and that food
availability plays a less important role
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Concept 53.6: The human population is no longer
growing exponentially but is still increasing rapidly
• No population can grow indefinitely, and
humans are no exception
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The Global Human Population
• The human population increased relatively
slowly until about 1650 and then began to grow
exponentially
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Fig. 53-22
6
5
4
3
2
The Plague
1
0
8000
B.C.E.
4000 3000
2000 1000
B.C.E. B.C.E. B.C.E. B.C.E.
0
1000
C.E.
2000
C.E.
Human population (billions)
7
• Though the global population is still growing,
the rate of growth began to slow during the
1960s
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Age Structure
• One important demographic factor in present
and future growth trends is a country’s age
structure
• Age structure is the relative number of
individuals at each age
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 53-25
Rapid growth
Afghanistan
Male
Female
10 8
6 4 2 0 2 4 6
Percent of population
Age
85+
80–84
75–79
70–74
65–69
60–64
55–59
50–54
45–49
40–44
35–39
30–34
25–29
20–24
15–19
10–14
5–9
0–4
8 10
8
Slow growth
United States
Male
Female
6 4 2 0 2 4 6
Percent of population
Age
85+
80–84
75–79
70–74
65–69
60–64
55–59
50–54
45–49
40–44
35–39
30–34
25–29
20–24
15–19
10–14
5–9
0–4
8
8
No growth
Italy
Male
Female
6 4 2 0 2 4 6 8
Percent of population
• Age structure diagrams can predict a
population’s growth trends
• They can illuminate social conditions and help
us plan for the future
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Global Carrying Capacity
• How many humans can the biosphere support?
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Estimates of Carrying Capacity
• The carrying capacity of Earth for humans is
uncertain
• The average estimate is 10–15 billion
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Limits on Human Population Size
• The ecological footprint concept summarizes
the aggregate land and water area needed to
sustain the people of a nation
• It is one measure of how close we are to the
carrying capacity of Earth
• Countries vary greatly in footprint size and
available ecological capacity
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 53-27
Log (g carbon/year)
13.4
9.8
5.8
Not analyzed
• Our carrying capacity could potentially be
limited by food, space, nonrenewable
resources, or buildup of wastes
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Chapter 54
Community Ecology
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Overview: A Sense of Community
• A biological community is an assemblage of
populations of various species living close
enough for potential interaction
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Concept 54.1: Community interactions are classified
by whether they help, harm, or have no effect on the
species involved
• Ecologists call relationships between species in
a community interspecific interactions
• Examples are competition, predation,
herbivory, and symbiosis (parasitism,
mutualism, and commensalism)
• Interspecific interactions can affect the survival
and reproduction of each species, and the
effects can be summarized as positive (+),
negative (–), or no effect (0)
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Competition
• Interspecific competition (–/– interaction)
occurs when species compete for a resource in
short supply
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Competitive Exclusion
• Strong competition can lead to competitive
exclusion, local elimination of a competing
species
• The competitive exclusion principle states that
two species competing for the same limiting
resources cannot coexist in the same place
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Ecological Niches
• The total of a species’ use of biotic and abiotic
resources is called the species’ ecological
niche
• An ecological niche can also be thought of as
an organism’s ecological role
• Ecologically similar species can coexist in a
community if there are one or more significant
differences in their niches
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• Resource partitioning is differentiation of
ecological niches, enabling similar species to
coexist in a community
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Fig. 54-2
A. distichus perches on fence
posts and other sunny surfaces.
A. insolitus usually perches
on shady branches.
A. ricordii
A. insolitus
A. aliniger
A. distichus
A. christophei
A. cybotes
A. etheridgei
• As a result of competition, a species’
fundamental niche may differ from its realized
niche
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 54-3
EXPERIMENT
Chthamalus
Balanus
High tide
Chthamalus
realized niche
Balanus
realized niche
Ocean
Low tide
RESULTS
High tide
Chthamalus
fundamental niche
Ocean
Low tide
Predation
• Predation (+/– interaction) refers to interaction
where one species, the predator, kills and eats
the other, the prey
• Some feeding adaptations of predators are
claws, teeth, fangs, stingers, and poison
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• Prey display various defensive adaptations
• Behavioral defenses include hiding, fleeing,
forming herds or schools, self-defense, and
alarm calls
• Animals also have morphological and
physiological defense adaptations
• Cryptic coloration, or camouflage, makes
prey difficult to spot
Video: Seahorse Camouflage
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Fig. 54-5a
(a) Cryptic
coloration
Canyon tree frog
• Animals with effective chemical defense often
exhibit bright warning coloration, called
aposematic coloration
• Predators are particularly cautious in dealing
with prey that display such coloration
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Fig. 54-5b
(b) Aposematic
coloration
Poison dart frog
• In some cases, a prey species may gain
significant protection by mimicking the
appearance of another species
• In Batesian mimicry, a palatable or harmless
species mimics an unpalatable or harmful
model
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Fig. 54-5c
(c) Batesian mimicry: A harmless species mimics a harmful one.
Hawkmoth
larva
Green parrot snake
• In Müllerian mimicry, two or more unpalatable
species resemble each other
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Fig. 54-5d
(d) Müllerian mimicry: Two unpalatable species
mimic each other.
Cuckoo bee
Yellow jacket
Herbivory
• Herbivory (+/– interaction) refers to an
interaction in which an herbivore eats parts of a
plant or alga
• It has led to evolution of plant mechanical and
chemical defenses and adaptations by
herbivores
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Symbiosis
• Symbiosis is a relationship where two or more
species live in direct and intimate contact with
one another
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Parasitism
• In parasitism (+/– interaction), one organism,
the parasite, derives nourishment from another
organism, its host, which is harmed in the
process
• Parasites that live within the body of their host
are called endoparasites; parasites that live
on the external surface of a host are
ectoparasites
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• Many parasites have a complex life cycle
involving a number of hosts
• Some parasites change the behavior of the
host to increase their own fitness
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Mutualism
• Mutualistic symbiosis, or mutualism (+/+
interaction), is an interspecific interaction that
benefits both species
• A mutualism can be
– Obligate, where one species cannot survive
without the other
– Facultative, where both species can survive
alone
Video: Clownfish and Anemone
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Fig. 54-7
(a) Acacia tree and ants (genus Pseudomyrmex)
(b) Area cleared by ants at the base of an acacia tree
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Commensalism
• In commensalism (+/0 interaction), one
species benefits and the other is apparently
unaffected
• Commensal interactions are hard to document
in nature because any close association likely
affects both species
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Fig. 54-8
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Concept 54.2: Dominant and keystone species
exert strong controls on community structure
• In general, a few species in a community exert
strong control on that community’s structure
• Two fundamental features of community
structure are species diversity and feeding
relationships
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Species Diversity
• Species diversity of a community is the
variety of organisms that make up the
community
• It has two components: species richness and
relative abundance
• Species richness is the total number of
different species in the community
• Relative abundance is the proportion each
species represents of the total individuals in the
community
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 54-9
A
B C D
Community 1
A: 25% B: 25% C: 25% D: 25%
Community 2
A: 80% B: 5% C: 5% D: 10%
Trophic Structure
• Trophic structure is the feeding relationships
between organisms in a community
• It is a key factor in community dynamics
• Food chains link trophic levels from producers
to top carnivores
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Fig. 54-11
Quaternary
consumers
Carnivore
Carnivore
Tertiary
consumers
Carnivore
Carnivore
Secondary
consumers
Carnivore
Carnivore
Primary
consumers
Herbivore
Zooplankton
Primary
producers
Plant
Phytoplankton
A terrestrial food chain
A marine food chain
Food Webs
• A food web is a branching food chain with
complex trophic interactions
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 54-12
Humans
Smaller
toothed
whales
Baleen
whales
Crab-eater
seals
Birds
Leopard
seals
Fishes
Sperm
whales
Elephant
seals
Squids
Carnivorous
plankton
Euphausids
(krill)
Copepods
Phytoplankton
Species with a Large Impact
• Certain species have a very large impact on
community structure
• Such species are highly abundant or play a
pivotal role in community dynamics
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Dominant Species
• Dominant species are those that are most
abundant or have the highest biomass
• Biomass is the total mass of all individuals in a
population
• Dominant species exert powerful control over
the occurrence and distribution of other species
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• One hypothesis suggests that dominant
species are most competitive in exploiting
resources
• Another hypothesis is that they are most
successful at avoiding predators
• Invasive species, typically introduced to a new
environment by humans, often lack predators
or disease. They can become dominant
species in a new ecosystem.
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Keystone Species
• Keystone species exert strong control on a
community by their ecological roles, or niches
• In contrast to dominant species, they are not
necessarily abundant in a community
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• Field studies of sea stars exhibit their role as a
keystone species in intertidal communities
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Fig. 54-15
EXPERIMENT
Number of species
present
RESULTS
20
15
With Pisaster (control)
10
5
Without Pisaster (experimental)
0
1963 ’64 ’65 ’66 ’67 ’68 ’69 ’70 ’71 ’72 ’73
Year
Concept 54.3: Disturbance influences species
diversity and composition
• Decades ago, most ecologists favored the view
that communities are in a state of equilibrium
• This view was supported by F. E. Clements
who suggested that species in a climax
community function as a superorganism
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• Other ecologists, including A. G. Tansley and
H. A. Gleason, challenged whether
communities were at equilibrium
• Recent evidence of change has led to a
nonequilibrium model, which describes
communities as constantly changing after
being buffeted by disturbances
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Characterizing Disturbance
• A disturbance is an event that changes a
community, removes organisms from it, and
alters resource availability
• Fire is a significant disturbance in most
terrestrial ecosystems
• It is often a necessity in some communities
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• The intermediate disturbance hypothesis
suggests that moderate levels of disturbance
can foster greater diversity than either high or
low levels of disturbance
• High levels of disturbance exclude many slowgrowing species
• Low levels of disturbance allow dominant
species to exclude less competitive species
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Ecological Succession
• Ecological succession is the sequence of
community and ecosystem changes after a
disturbance
• Primary succession occurs where no soil
exists when succession begins
• Secondary succession begins in an area
where soil remains after a disturbance
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Ecological Succession
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Chapter 55
Ecosystems
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Overview: Observing Ecosystems
• An ecosystem consists of all the organisms
living in a community, as well as the abiotic
factors with which they interact
• Ecosystems range from a microcosm, such as
an aquarium, to a large area such as a lake or
forest
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
• Regardless of an ecosystem’s size, its
dynamics involve two main processes: energy
flow and chemical cycling
• Energy flows through ecosystems while matter
cycles within them
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Concept 55.1: Physical laws govern energy flow
and chemical cycling in ecosystems
• Ecologists study the transformations of energy
and matter within their system
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Conservation of Energy
• Laws of physics and chemistry apply to
ecosystems, particularly energy flow
• The first law of thermodynamics states that
energy cannot be created or destroyed, only
transformed
• Energy enters an ecosystem as solar radiation,
is conserved, and is lost from organisms as
heat
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• The second law of thermodynamics states that
every exchange of energy increases the
entropy of the universe
• In an ecosystem, energy conversions are not
completely efficient, and some energy is
always lost as heat
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Conservation of Mass
• The law of conservation of mass states that
matter cannot be created or destroyed
• Chemical elements are continually recycled
within ecosystems
• In a forest ecosystem, most nutrients enter as
dust or solutes in rain and are carried away in
water
• Ecosystems are open systems, absorbing
energy and mass and releasing heat and waste
products
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Energy, Mass, and Trophic Levels
• Autotrophs build molecules themselves using
photosynthesis or chemosynthesis as an
energy source; heterotrophs depend on the
biosynthetic output of other organisms
• Energy and nutrients pass from primary
producers (autotrophs) to primary
consumers (herbivores) to secondary
consumers (carnivores) to tertiary
consumers (carnivores that feed on other
carnivores)
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• Detritivores, or decomposers, are consumers
that derive their energy from detritus, nonliving
organic matter
• Prokaryotes and fungi are important
detritivores
• Decomposition connects all trophic levels
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 55-4
Tertiary consumers
Microorganisms
and other
detritivores
Detritus
Secondary
consumers
Primary consumers
Primary producers
Heat
Key
Chemical cycling
Energy flow
Sun
Ecosystem Energy Budgets
• The amount of light energy converted to
chemical energy by autotrophs is an
ecosystem’s primary production
• The extent of photosynthetic production sets
the spending limit for an ecosystem’s energy
budget
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Global Energy Budget
• The amount of solar radiation reaching the
Earth’s surface limits photosynthetic output of
ecosystems
• Only a small fraction of solar energy actually
strikes photosynthetic organisms, and even
less is of a usable wavelength
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Gross and Net Primary Production
• Total primary production is known as the
ecosystem’s gross primary production (GPP)
• Net primary production (NPP) is GPP minus
energy used by primary producers for respiration
• Only NPP is available to consumers
• Ecosystems vary greatly in NPP and contribution
to the total NPP on Earth
• Standing crop is the total biomass of
photosynthetic autotrophs at a given time
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 55-5
TECHNIQUE
80
Snow
Clouds
60
Vegetation
40
Soil
20
Liquid water
0
400
600
Visible
800
1,000
Near-infrared
Wavelength (nm)
1,200
• Tropical rain forests, estuaries, and coral reefs
are among the most productive ecosystems
per unit area
• Marine ecosystems are relatively unproductive
per unit area, but contribute much to global net
primary production because of their volume
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 55-6
Net primary production (kg carbon/m2·yr)
·
0
1
2
3
Primary Production in Aquatic Ecosystems
• In marine and freshwater ecosystems, both
light and nutrients control primary production
• Depth of light penetration affects primary
production in the photic zone of an ocean or
lake
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Nutrient Limitation
• More than light, nutrients limit primary production
in geographic regions of the ocean and in lakes
• A limiting nutrient is the element that must be
added for production to increase in an area
• Nitrogen and phosphorous are typically the
nutrients that most often limit marine production
• Nutrient enrichment experiments confirmed that
nitrogen was limiting phytoplankton growth off the
shore of Long Island, New York
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 55-7
EXPERIMENT
B
C
D
E
F
G
Shinnecock
Bay
Moriches Bay
Atlantic Ocean
A
Phytoplankton density
(millions of cells per mL)
RESULTS
30
Ammonium
enriched
24
Phosphate
enriched
18
Unenriched
control
12
6
0
A
B
C
D
E
Collection site
F
G
• Upwelling of nutrient-rich waters in parts of the
oceans contributes to regions of high primary
production
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
• The addition of large amounts of nutrients to
lakes has a wide range of ecological impacts
• In some areas, sewage runoff has caused
eutrophication of lakes, which can lead to
loss of most fish species
Video: Cyanobacteria (Oscillatoria)
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Primary Production in Terrestrial Ecosystems
• In terrestrial ecosystems, temperature and
moisture affect primary production on a large
scale
• Actual evapotranspiration can represent the
contrast between wet and dry climates
• Actual evapotranspiration is the water
annually transpired by plants and evaporated
from a landscape
• It is related to net primary production
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 55-8
Net primary production (g/m2··yr)
3,000
Tropical forest
2,000
Temperate forest
1,000
Mountain coniferous forest
Desert
shrubland
Temperate grassland
Arctic tundra
0
0
500
1,500
1,000
Actual evapotranspiration (mm H2O/yr)
• On a more local scale, a soil nutrient is often
the limiting factor in primary production
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Concept 55.3: Energy transfer between trophic
levels is typically only 10% efficient
• Secondary production of an ecosystem is the
amount of chemical energy in food converted
to new biomass during a given period of time
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Production Efficiency
• When a caterpillar feeds on a leaf, only about
one-sixth of the leaf’s energy is used for
secondary production
• An organism’s production efficiency is the
fraction of energy stored in food that is not
used for respiration
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 55-9
Plant material
eaten by caterpillar
200 J
67 J
Feces
100 J
33 J
Growth (new biomass)
Cellular
respiration
Trophic Efficiency and Ecological Pyramids
• Trophic efficiency is the percentage of
production transferred from one trophic level to
the next
• It usually ranges from 5% to 20%
• Trophic efficiency is multiplied over the length
of a food chain
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
• Approximately 0.1% of chemical energy fixed
by photosynthesis reaches a tertiary consumer
• A pyramid of net production represents the loss
of energy with each transfer in a food chain
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 55-10
Tertiary
consumers
Secondary
consumers
10 J
100 J
Primary
consumers
1,000 J
Primary
producers
10,000 J
1,000,000 J of sunlight
• In a biomass pyramid, each tier represents the
dry weight of all organisms in one trophic level
• Most biomass pyramids show a sharp
decrease at successively higher trophic levels
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• Dynamics of energy flow in ecosystems have
important implications for the human population
• Eating meat is a relatively inefficient way of
tapping photosynthetic production
• Worldwide agriculture could feed many more
people if humans ate only plant material
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Concept 55.4: Biological and geochemical
processes cycle nutrients between organic and
inorganic parts of an ecosystem
• Life depends on recycling chemical elements
• Nutrient circuits in ecosystems involve biotic
and abiotic components and are often called
biogeochemical cycles
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Biogeochemical Cycles
• Gaseous carbon, oxygen, sulfur, and nitrogen
occur in the atmosphere and cycle globally
• Less mobile elements such as phosphorus,
potassium, and calcium cycle on a more local
level
• A model of nutrient cycling includes main
reservoirs of elements and processes that
transfer elements between reservoirs
• All elements cycle between organic and
inorganic reservoirs
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
• In studying cycling of water, carbon, nitrogen,
and phosphorus, ecologists focus on four
factors:
– Each chemical’s biological importance
– Forms in which each chemical is available or
used by organisms
– Major reservoirs for each chemical
– Key processes driving movement of each
chemical through its cycle
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The Water Cycle
• Water is essential to all organisms
• 97% of the biosphere’s water is contained in
the oceans, 2% is in glaciers and polar ice
caps, and 1% is in lakes, rivers, and
groundwater
• Water moves by the processes of evaporation,
transpiration, condensation, precipitation, and
movement through surface and groundwater
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 55-14a
Transport
over land
Solar energy
Net movement of
water vapor by wind
Precipitation Evaporation
over ocean
from ocean
Precipitation
over land
Evapotranspiration
from land
Percolation
through
soil
Runoff and
groundwater
The Carbon Cycle
• Carbon-based organic molecules are essential
to all organisms
• Carbon reservoirs include fossil fuels, soils and
sediments, solutes in oceans, plant and animal
biomass, and the atmosphere
• CO2 is taken up and released through
photosynthesis and respiration; additionally,
volcanoes and the burning of fossil fuels
contribute CO2 to the atmosphere
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 55-14b
CO2 in atmosphere
Photosynthesis
Photosynthesis
Cellular
respiration
Burning of
fossil fuels Phytoand wood plankton
Higher-level
consumers
Primary
consumers
Carbon compounds
in water
Detritus
Decomposition
The Terrestrial Nitrogen Cycle
• Nitrogen is a component of amino acids,
proteins, and nucleic acids
• The main reservoir of nitrogen is the
atmosphere (N2), though this nitrogen must be
converted to NH4+ or NO3– for uptake by plants,
via nitrogen fixation by bacteria
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• Organic nitrogen is decomposed to NH4+ by
ammonification, and NH4+ is decomposed to
NO3– by nitrification
• Denitrification converts NO3– back to N2
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Fig. 55-14c
N2 in atmosphere
Assimilation
NO3–
Nitrogen-fixing
bacteria
Decomposers
Ammonification
NH3
Nitrogen-fixing
soil bacteria
Nitrification
NH4+
NO2–
Nitrifying
bacteria
Denitrifying
bacteria
Nitrifying
bacteria
The Phosphorus Cycle
• Phosphorus is a major constituent of nucleic
acids, phospholipids, and ATP
• Phosphate (PO43–) is the most important
inorganic form of phosphorus
• The largest reservoirs are sedimentary rocks of
marine origin, the oceans, and organisms
• Phosphate binds with soil particles, and
movement is often localized
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Fig. 55-14d
Precipitation
Geologic
uplift
Weathering
of rocks
Runoff
Consumption
Decomposition
Plant
uptake
of PO43–
Plankton Dissolved PO43–
Uptake
Sedimentation
Soil
Leaching
Decomposition and Nutrient Cycling Rates
• Decomposers (detritivores) play a key role in
the general pattern of chemical cycling
• Rates at which nutrients cycle in different
ecosystems vary greatly, mostly as a result of
differing rates of decomposition
• The rate of decomposition is controlled by
temperature, moisture, and nutrient availability
• Rapid decomposition results in relatively low
levels of nutrients in the soil
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Case Study: Nutrient Cycling in the Hubbard
Brook Experimental Forest
• Vegetation strongly regulates nutrient cycling
• Research projects monitor ecosystem
dynamics over long periods
• The Hubbard Brook Experimental Forest has
been used to study nutrient cycling in a forest
ecosystem since 1963
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• The research team constructed a dam on the
site to monitor loss of water and minerals
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Fig. 55-16
(a) Concrete dam
and weir
Nitrate concentration in runoff
(mg/L)
(b) Clear-cut watershed
80
60
40
20
4
3
2
1
0
Deforested
Completion of
tree cutting
1965
Control
1966
(c) Nitrogen in runoff from watersheds
1967
1968
Fig. 55-16a
(a) Concrete dam and weir
• In one experiment, the trees in one valley were
cut down, and the valley was sprayed with
herbicides
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Fig. 55-16b
(b) Clear-cut watershed
• Net losses of water and minerals were studied
and found to be greater than in an undisturbed
area
• These results showed how human activity can
affect ecosystems
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Nitrate concentration in runoff
(mg/L)
Fig. 55-16c
80
Deforested
60
40
20
4
3
Completion of
tree cutting
Control
2
1
0
1965
1966
(c) Nitrogen in runoff from watersheds
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1967
1968
Concept 55.5: Human activities now dominate
most chemical cycles on Earth
• As the human population has grown, our
activities have disrupted the trophic structure,
energy flow, and chemical cycling of many
ecosystems
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Nutrient Enrichment
• In addition to transporting nutrients from one
location to another, humans have added new
materials, some of them toxins, to ecosystems
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Agriculture and Nitrogen Cycling
• The quality of soil varies with the amount of
organic material it contains
• Agriculture removes from ecosystems nutrients
that would ordinarily be cycled back into the
soil
• Nitrogen is the main nutrient lost through
agriculture; thus, agriculture greatly affects the
nitrogen cycle
• Industrially produced fertilizer is typically used
to replace lost nitrogen, but effects on an
ecosystem can be harmful
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Contamination of Aquatic Ecosystems
• Critical load for a nutrient is the amount that
plants can absorb without damaging the
ecosystem
• When excess nutrients are added to an
ecosystem, the critical load is exceeded
• Remaining nutrients can contaminate
groundwater as well as freshwater and marine
ecosystems
• Sewage runoff causes cultural eutrophication,
excessive algal growth that can greatly harm
freshwater ecosystems
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Fig. 55-18
The dead zone arising from nitrogen pollution in
the Mississippi basin
Winter
Summer
Acid Precipitation
• Combustion of fossil fuels is the main cause of
acid precipitation
• North American and European ecosystems
downwind from industrial regions have been
damaged by rain and snow containing nitric
and sulfuric acid
• Acid precipitation changes soil pH and causes
leaching of calcium and other nutrients
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• Environmental regulations and new
technologies have allowed many developed
countries to reduce sulfur dioxide emissions
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Toxins in the Environment
• Humans release many toxic chemicals,
including synthetics previously unknown to
nature
• In some cases, harmful substances persist for
long periods in an ecosystem
• One reason toxins are harmful is that they
become more concentrated in successive
trophic levels
• Biological magnification concentrates toxins
at higher trophic levels, where biomass is lower
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• PCBs and many pesticides such as DDT are
subject to biological magnification in
ecosystems
• In the 1960s Rachel Carson brought attention
to the biomagnification of DDT in birds in her
book Silent Spring
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Greenhouse Gases and Global Warming
• One pressing problem caused by human
activities is the rising level of atmospheric
carbon dioxide
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Rising Atmospheric CO2 Levels
• Due to the burning of fossil fuels and other
human activities, the concentration of
atmospheric CO2 has been steadily increasing
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Fig. 55-21
14.9
390
14.8
380
14.7
14.6
370
Temperature
14.5
360
14.4
14.3
350
14.2
340
14.1
CO2
330
14.0
13.9
320
13.8
310
13.7
13.6
300
1960
1965
1970
1975
1980 1985
Year
1990
1995
2000
2005
The Greenhouse Effect and Climate
• CO2, water vapor, and other greenhouse gases
reflect infrared radiation back toward Earth; this
is the greenhouse effect
• This effect is important for keeping Earth’s
surface at a habitable temperature
• Increased levels of atmospheric CO2 are
magnifying the greenhouse effect, which could
cause global warming and climatic change
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• Increasing concentration of atmospheric CO2 is
linked to increasing global temperature
• Northern coniferous forests and tundra show
the strongest effects of global warming
• A warming trend would also affect the
geographic distribution of precipitation
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• Global warming can be slowed by reducing
energy needs and converting to renewable
sources of energy
• Stabilizing CO2 emissions will require an
international effort
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Depletion of Atmospheric Ozone
• Life on Earth is protected from damaging
effects of UV radiation by a protective layer of
ozone molecules in the atmosphere
• Satellite studies suggest that the ozone layer
has been gradually thinning since 1975
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• Destruction of atmospheric ozone probably
results from chlorine-releasing pollutants such
as CFCs produced by human activity
• Scientists first described an “ozone hole” over
Antarctica in 1985; it has increased in size as
ozone depletion has increased
• CFCs have been banned and are no longer
used in this country. They will, however, still be
in the atmosphere affecting the ozone for a
long time.
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Chapter 56
Conservation Biology and
Restoration Ecology
PowerPoint® Lecture Presentations for
Biology
Eighth Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Overview: Striking Gold
• 1.8 million species have been named and
described
• Biologists estimate 10–200 million species
exist on Earth
• Tropical forests contain some of the greatest
concentrations of species and are being
destroyed at an alarming rate
• Humans are rapidly pushing many species
toward extinction
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Concept 56.1: Human activities threaten Earth’s
biodiversity
• Rates of species extinction are difficult to
determine under natural conditions
• The high rate of species extinction is largely a
result of ecosystem degradation by humans
• Humans are threatening Earth’s biodiversity
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Three Levels of Biodiversity
• Biodiversity has three main components:
– Genetic diversity
– Species diversity
– Ecosystem diversity
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Genetic Diversity
• Genetic diversity comprises genetic variation
within a population and between populations
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Species Diversity
• Species diversity is the variety of species in an
ecosystem or throughout the biosphere
• According to the U.S. Endangered Species Act:
–
An endangered species is “in danger of
becoming extinct throughout all or a significant
portion of its range”
– A threatened species is likely to become
endangered in the foreseeable future
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• Conservation biologists are concerned about
species loss because of alarming statistics
regarding extinction and biodiversity
• Globally, 12% of birds, 20% of mammals, and
32% of amphibians are threatened with
extinction
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Ecosystem Diversity
• Human activity is reducing ecosystem diversity,
the variety of ecosystems in the biosphere
• More than 50% of wetlands in the contiguous
United States have been drained and
converted to other ecosystems
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Biodiversity and Human Welfare
• Human biophilia allows us to recognize the
value of biodiversity for its own sake
• Species diversity brings humans practical
benefits
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Benefits of Species and Genetic Diversity
• In the United States, 25% of prescriptions
contain substances originally derived from
plants
• For example, the rosy periwinkle contains
alkaloids that inhibit cancer growth
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Fig. 56-6
• The loss of species also means loss of genes
and genetic diversity
• The enormous genetic diversity of organisms
has potential for great human benefit
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Ecosystem Services
• Ecosystem services encompass all the
processes through which natural ecosystems
and their species help sustain human life
• Some examples of ecosystem services:
– Purification of air and water
– Detoxification and decomposition of wastes
– Cycling of nutrients
– Moderation of weather extremes
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Three Threats to Biodiversity
• Most species loss can be traced to three major
threats:
– Habitat destruction
– Introduced species
– Overexploitation
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Habitat Loss
• Human alteration of habitat is the greatest
threat to biodiversity throughout the biosphere
• In almost all cases, habitat fragmentation and
destruction lead to loss of biodiversity
• For example
– In Wisconsin, prairie occupies <0.1% of its
original area
– About 93% of coral reefs have been damaged
by human activities
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Introduced Species
• Introduced species are those that humans
move from native locations to new geographic
regions
• Without their native predators, parasites, and
pathogens, introduced species may spread
rapidly
• Introduced species that gain a foothold in a
new habitat usually disrupt their adopted
community
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• Sometimes humans introduce species by
accident, as in case of the brown tree snake
arriving in Guam as a cargo ship “stowaway”
• The main food source for the brown tree snake
was birds. Guam now has no birds left on the
island due to the introduction of this snake.
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Fig. 56-8a
(a) Brown tree snake
• Humans have deliberately introduced some
species with good intentions but disastrous
effects
• An example is the introduction of kudzu in the
southern United States
• This bushy weed grows so fast it can cover
large areas in very little time, crowding out
other native plants
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Fig. 56-8b
(b) Kudzu
Overexploitation
• Overexploitation is human harvesting of wild
plants or animals at rates exceeding the ability
of populations of those species to rebound
• Overexploitation by the fishing industry has
greatly reduced populations of some game fish,
such as bluefin tuna and Atlantic cod
• Passenger pigeons once numbered in the
millions but were hunted to extinction
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Concept 56.3: Landscape and regional
conservation aim to sustain entire biotas
• Conservation biology has attempted to sustain
the biodiversity of entire communities,
ecosystems, and landscapes
• Ecosystem management is part of landscape
ecology, which seeks to make biodiversity
conservation part of land-use planning
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Landscape Structure and Biodiversity
• The structure of a landscape can strongly
influence biodiversity
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• The Biological Dynamics of Forest Fragments
Project in the Amazon examines the effects of
fragmentation on biodiversity
• Landscapes dominated by fragmented habitats
support fewer species due to a loss of species
adapted to habitat interiors
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Corridors That Connect Habitat Fragments
• A movement corridor is a narrow strip of
quality habitat connecting otherwise isolated
patches
• Movement corridors promote dispersal and
help sustain populations
• In areas of heavy human use, artificial corridors
are sometimes constructed
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Fig. 56-16
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Establishing Protected Areas
• Conservation biologists apply understanding of
ecological dynamics in establishing protected
areas to slow the loss of biodiversity
• Much of their focus has been on hot spots of
biological diversity
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Finding Biodiversity Hot Spots
• A biodiversity hot spot is a relatively small
area with a great concentration of endemic
species and many endangered and threatened
species
• Biodiversity hot spots are good choices for
nature reserves, but identifying them is not
always easy
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Concept 56.4: Restoration ecology attempts to
restore degraded ecosystems to a more natural state
• Given enough time, biological communities can
recover from many types of disturbances
• Restoration ecology seeks to initiate or speed
up the recovery of degraded ecosystems
• A basic assumption of restoration ecology is
that most environmental damage is reversible
• Two key strategies are bioremediation and
augmentation of ecosystem processes
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Fig. 56-21
(a) In 1991, before restoration
(b) In 2000, near the completion of restoration
Bioremediation
• Bioremediation is the use of living organisms
to detoxify ecosystems
• The organisms most often used are
prokaryotes, fungi, or plants
• These organisms can take up, and sometimes
metabolize, toxic molecules
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Biological Augmentation
• Biological augmentation uses organisms to
add essential materials to a degraded
ecosystem
• For example, nitrogen-fixing plants can
increase the available nitrogen in soil
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