THE ECOLOGICAL STUFF….
 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
Fig. 52-2
Organismal
ecology
Population
ecology
Community
ecology
Ecosystem
ecology
Landscape
ecology
Global
ecology
 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
 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
 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
Fig. 52-2f
 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
Fig. 52-4
 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
Fig. 52-5
Kangaroos/km2
0–0.1
0.1–1
1–5
5–10
10–20
> 20
Limits of
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
 Natural range expansions show the influence of
dispersal on distribution
Fig. 52-7
Current
1970
1966
1965
1960
1961
1943
1958
1937
1951
1956
1970
 Species transplants include organisms that are
intentionally or accidentally relocated from their
original distribution
 Species transplants can disrupt the communities
or ecosystems to which they have been
introduced
 Some organisms do not occupy all of their
potential range
 Species distribution may be limited by habitat
selection behavior
 Biotic factors that affect the distribution of
organisms may include:
 Interactions with other species
 Predation
 Competition
Fig. 52-8
RESULTS
100
Seaweed cover (%)
80
Both limpets and urchins
removed
Sea urchin
Only urchins
removed
60
Limpet
40
Only limpets removed
Control (both urchins
and limpets present)
20
0
August
1982
February
1983
August
1983
February
1984
 Abiotic factors affecting distribution of organisms
include:
 Temperature
 Water
 Sunlight
 Wind
 Rocks and soil
 Most abiotic factors vary in space and time
 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
Fig. 52-10a
Latitudinal Variation in Sunlight Intensity
90ºN (North Pole)
60ºN
Low angle of incoming sunlight
30ºN
23.5ºN (Tropic of
Cancer)
Sun directly overhead at equinoxes
0º (equator)
23.5ºS (Tropic of
Capricorn)
30ºS
Low angle of incoming sunlight
60ºS
90ºS (South Pole)
Atmosphere
Seasonal Variation in Sunlight Intensity
60ºN
30ºN
March equinox
0º (equator)
June solstice
30ºS
Constant tilt
of 23.5º
September equinox
December solstice
Fig. 52-10e
60ºN
30ºN
Descending
dry air
absorbs
moisture
0º
(equator)
Descending
dry air
absorbs
moisture
Ascending
moist air
releases
moisture
30ºS
60ºS
30º 23.5º
Arid
zone
0º
Tropics
23.5º 30º
Arid
zone
Fig. 52-10f
66.5ºN
(Arctic Circle)
60ºN
Westerlies
30ºN
Northeast trades
Doldrums
Southeast trades
0º
(equator)
30ºS
Westerlies
60ºS
66.5ºS
(Antarctic Circle)
Bodies of Water
 The Gulf Stream carries warm water from the
equator to the North Atlantic
 Oceans and their currents and large lakes
moderate the climate of nearby terrestrial
environments
Fig. 52-11
Labrador
current
Gulf
stream
Equator
Cold water
Fig. 52-12
Air cools at
high elevation.
2
3 Cooler
air sinks
over water.
1 Warm air
over land rises.
4 Cool air over water
moves inland, replacing
rising warm air over land.
Mountains
 Mountains have a significant effect on
 The amount of sunlight reaching an area
 Local temperature
 Rainfall
 Rising air releases moisture on the windward side
of a peak and creates a “rain shadow” as it
absorbs moisture on the leeward side
Fig. 52-13
Wind
direction
Leeward side
of mountain
Mountain
range
Ocean
 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
Fig. 52-15
30ºN
Tropic of
Cancer
Equator
Tropic of
Capricorn
30ºS
Lakes
Coral reefs
Rivers
Oceanic
pelagic and
benthic zones
Estuaries
Intertidal zones
Fig. 52-16b
Intertidal zone
Neritic zone
0
Oceanic zone
Photic zone
200 m
Continental
shelf
Pelagic
zone
Benthic
zone
2,000–6,000 m
Abyssal zone
(b) Marine zonation
Aphotic
zone
 The upper photic zone has sufficient light for
photosynthesis while the lower aphotic zone
receives little light
 The organic and inorganic sediment at the
bottom of all aquatic zones is called the benthic
zone
 The communities of organisms in the benthic
zone are collectively called the benthos
 Detritus, dead organic matter, falls from the
productive surface water and is an important
source of food
 The most extensive part of the ocean is the
abyssal zone with a depth of 2,000 to 6,000 m
Fig. 52-16a
Littoral
zone
Limnetic
zone
Photic
zone
Benthic
zone
(a) Zonation in a lake
Pelagic
zone
Aphotic
zone
Fig. 52-17-5
Winter
Summer
Spring
2º
4º
4º
4º
4ºC
0º
4º
4º
Autumn
20º
18º
8º
6º
5º
4ºC
4º
4º
4º
4ºC
Thermocline
22º
4º
4º
4º
4º
4ºC
4º
Terrestrial Biomes
 Terrestrial biomes can be characterized by
distribution, precipitation, temperature, plants,
and animals
Tropical Forest
 In tropical rain forests, rainfall is relatively
constant, while in tropical dry forests
precipitation is highly seasonal
 Tropical forests are vertically layered and
competition for light is intense
 Tropical forests are home to millions of animal
species, including an estimated 5–30 million still
undescribed species of insects, spiders, and other
arthropods
Fig. 52-21a
A tropical rain forest in Borneo
Desert
 Precipitation is low and highly variable, generally
less than 30 cm per year; deserts may be hot or
cold
 Desert plants are adapted for heat and
desiccation tolerance, water storage, and reduced
leaf surface area
 Common desert animals include many kinds of
snakes and lizards, scorpions, ants, beetles,
migratory and resident birds, and seed-eating
rodents; many are nocturnal
Fig. 52-21b
A desert in the southwestern
United States
Savanna
 Savanna precipitation and temperature are
seasonal
 Grasses and forbs make up most of the ground
cover
 Common inhabitants include insects and
mammals such as wildebeests, zebras, lions, and
hyenas
Fig. 52-21c
A savanna in Kenya
Chaparral
 Chaparral climate is highly seasonal, with cool
and rainy winters and hot dry summers
 The chaparral is dominated by shrubs, small
trees, grasses, and herbs; many plants are
adapted to fire and drought
 Animals include amphibians, birds and other
reptiles, insects, small mammals and browsing
mammals
Fig. 52-21d
An area of chaparral
in California
Temperate Grassland
 Temperate grasslands are found on many
continents
 Winters are cold and dry, while summers are wet
and hot
 The dominant plants, grasses and forbs, are
adapted to droughts and fire
 Native mammals include large grazers and small
burrowers
Fig. 52-21e
Sheyenne National Grassland
in North Dakota
Northern Coniferous Forest
 The northern coniferous forest, or taiga,
extends across northern North America and
Eurasia and is the largest terrestrial biome on
Earth
 Winters are cold and long while summers may be
hot
 The conical shape of conifers prevents too much
snow from accumulating and breaking their
branches
 Animals include migratory and resident birds,
and large mammals
Fig. 52-21f
Rocky Mountain National Park
in Colorado
Temperate Broadleaf Forest
 Winters are cool, while summers are hot and
humid; significant precipitation falls year round
as rain and snow
 A mature temperate broadleaf forest has
vertical layers dominated by deciduous trees in
the Northern Hemisphere and evergreen
eucalyptus in Australia
 Mammals, birds, and insects make use of all
vertical layers in the forest
 In the Northern Hemisphere, many mammals
hibernate in the winter
Fig. 52-21g
Great Smoky Mountains
National Park in North Carolina
Tundra
 Tundra covers expansive areas of the Arctic;
alpine tundra exists on high mountaintops at all
latitudes
 Winters are long and cold while summers are
relatively cool; precipitation varies
 Permafrost, a permanently frozen layer of soil,
prevents water infiltration
 Vegetation is herbaceous (mosses, grasses, forbs,
dwarf shrubs and trees, and lichen) and supports
birds, grazers, and their predators
Fig. 52-21h
Denali National Park, Alaska,
in autumn
 Population ecology is the study of populations
in relation to environment, including
environmental influences on density and
distribution, age structure, and population size
 A population is a group of individuals of a single
species living in the same general area
 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
Fig. 53-3
Births
Births and immigration
add individuals to
a population.
Immigration
Deaths
Deaths and emigration
remove individuals
from a population.
Emigration
 Environmental and social factors influence
spacing of individuals in a population
 In a clumped dispersion, individuals aggregate in
patches
 A clumped dispersion may be influenced by
resource availability and behavior
Fig. 53-4
(a) Clumped
(b) Uniform
(c) Random
 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
 The life table of Belding’s ground squirrels
reveals many things about this population
Table 53-1
 A survivorship curve is a graphic way of
representing the data in a life table
 The survivorship curve for Belding’s ground
squirrels shows a relatively constant death rate
Fig. 53-5
Number of survivors (log scale)
1,000
100
Females
10
Males
1
0
2
4
6
Age (years)
8
10
 Survivorship curves can be classified into three
general types:
 Type I: low death rates during early and middle life, then
an increase among older age groups
 Type II: the death rate is constant over the organism’s life
span
 Type III: high death rates for the young, then a slower
death rate for survivors
Number of survivors (log scale)
Fig. 53-6
1,000
I
100
II
10
III
1
0
50
Percentage of maximum life span
100
 For species with sexual reproduction,
demographers often concentrate on females in a
population
 A reproductive table, or fertility schedule, is an
age-specific summary of the reproductive rates in
a population
 It describes reproductive patterns of a population
Table 53-2
Fig. 53-9
(a) Dandelion
(b) Coconut palm
 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
Fig. 53-11
Elephant population
8,000
6,000
4,000
2,000
0
1900
1920
1940
Year
1960
1980
 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
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
 Some populations overshoot K before settling
down to a relatively stable density
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
 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
 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
Fig. 53-15
Birth or death rate
per capita
Density-dependent
birth rate
Density-dependent
birth rate
Densitydependent
death rate
Equilibrium
density
Equilibrium
density
Population density
(a) Both birth rate and death rate vary.
Birth or death rate
per capita
Densityindependent
death rate
Densityindependent
birth rate
Density-dependent
death rate
Equilibrium
density
Population density
(c) Death rate varies; birth rate is constant.
Population density
(b) Birth rate varies; death rate is constant.
 Population density can influence the health and
survival of organisms
 In dense populations, pathogens can spread
more rapidly
 As a prey population builds up, predators may
feed preferentially on that species
 Accumulation of toxic wastes can contribute to
density-dependent regulation of population size
 For some populations, intrinsic (physiological)
factors appear to regulate population size
 The study of population dynamics focuses on
the complex interactions between biotic and
abiotic factors that cause variation in population
size
 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
Fig. 53-18
2,100
1,900
Number of sheep
1,700
1,500
1,300
1,100
900
700
500
0
1955
1965
1975
1985
Year
1995
2005
Fig. 53-19
2,500
50
Moose
40
2,000
30
1,500
20
1,000
10
500
0
1955
0
1965
1975
1985
Year
1995
2005
Number of moose
Number of wolves
Wolves
Fig. 53-20
Number of hares
(thousands)
120
9
Lynx
80
6
40
3
0
0
1850
1875
1900
Year
1925
Number of lynx
(thousands)
Snowshoe hare
160
 No population can grow indefinitely, and
humans are no exception
7
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)
Fig. 53-22
 To maintain population stability, a regional
human population can exist in one of two
configurations:
 Zero population growth =
High birth rate – High death rate
 Zero population growth =
Low birth rate – Low death rate
 The demographic transition is the move from
the first state toward the second state
 The demographic transition is associated with an
increase in the quality of health care and
improved access to education, especially for
women
 Most of the current global population growth is
concentrated in developing countries
 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
 Age structure diagrams can predict a population’s
growth trends
 They can illuminate social conditions and help us
plan for the future
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
 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
Fig. 53-27
Log (g carbon/year)
13.4
9.8
5.8
Not analyzed