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Chapter 50
An Introduction to Ecology
and the Biosphere
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
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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 both the distribution of organisms
and their abundance
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• Ecology
– Is an enormously complex and exciting area of
biology
– Reveals the richness of the biosphere
Figure 50.1
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• Concept 50.1: Ecology is the study of
interactions between organisms and the
environment
• Ecology
– Has a long history as a descriptive science
– Is also a rigorous experimental science
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Ecology and Evolutionary Biology
• Events that occur in ecological time
– Affect life on the scale of evolutionary time
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Organisms and the Environment
• The environment of any organism includes
– Abiotic, or nonliving components - physical
factors such as temperature, light, water, and
nutrients
– Biotic, or living components - All the organisms
living in the environment, the biota
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• Environmental components
– Affect the distribution and abundance of
organisms
Kangaroos/km2
> 20
10–20
5–10
1–5
0.1–1
< 0.1
Limits of
distribution
Figure 50.2
Climate in northern Australia
is hot and wet, with seasonal
drought.
Southern Australia has
cool, moist winters and
warm, dry summers.
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Red kangaroos
occur in most
semiarid and arid
regions of the
interior, where
precipitation is
relatively low and
variable from
year to year.
Southeastern Australia
has a wet, cool climate.
Tasmania
• Ecologists
– Use observations and experiments to test
explanations for the distribution and
abundance of species
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Subfields of Ecology
• Organismal ecology
– Studies how an organism’s structure,
physiology, and (for animals) behavior meet
the challenges posed by the environment
Figure 50.3a
(a) Organismal ecology. How do humpback whales
select their calving areas?
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• Population ecology
– Concentrates mainly on factors that affect how
many individuals of a particular species live in
an area
(b) Population ecology.
What environmental
factors affect the
reproductive rate of
deer mice?
Figure 50.3b
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• Community ecology
– Deals with the whole array of interacting
species in a community
(c) Community ecology.
What factors influence
the diversity of species
that make up a
particular forest?
Figure 50.3c
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• Ecosystem ecology
– Emphasizes energy flow and chemical cycling
among the various biotic and abiotic
components
(d) Ecosystem ecology. What
factors control photosynthetic
productivity in a temperate
grassland ecosystem?
Figure 50.3d
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• Landscape ecology
– Deals with arrays of ecosystems and how they
are arranged in a geographic region
Figure 50.3e
(e) Landscape ecology. To what extent do the trees lining the
drainage channels in this landscape serve as corridors of
dispersal for forest animals?
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• The biosphere
– Is the global ecosystem, the sum of all the
planet’s ecosystems
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Ecology and Environmental Issues
• Ecology
– Provides the scientific understanding
underlying environmental issues
• Rachel Carson
– Is credited
with starting
the modern
environmental
movement
Figure 50.4
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• Most ecologists follow the precautionary
principle regarding environmental issues
• The precautionary principle
– Basically states that humans need to be
concerned with how their actions affect the
environment
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• Concept 50.2: 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
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• Many naturalists
– Began to identify broad patterns of distribution
by naming biogeographic realms
Palearctic
Nearctic
Tropic
of Cancer
(23.5N)
Oriental
Ethiopian
Equator
Neotropical
Figure 50.5
(23.5S)
Tropic of
Capricorn
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Australian
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• Biogeography
– Provides a good starting point for
understanding what limits the geographic
distribution of species
Species absent
because
Yes
Dispersal
limits
distribution?
No
Area inaccessible
or insufficient time
Behavior
limits
distribution?
Yes
Habitat selection
Yes
No
Biotic factors
(other species)
limit
distribution?
No
Predation, parasitism, Chemical
competition, disease factors
Water
Abiotic factors
limit
distribution?
Oxygen
Salinity
pH
Soil nutrients, etc.
Temperature
Physical Light
factors Soil structure
Fire
Moisture, etc.
Figure 50.6
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Dispersal and Distribution
• Dispersal
– Is the movement of individuals away from
centers of high population density or from their
area of origin
– Contributes to the global distribution of
organisms
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Natural Range Expansions
• Natural range expansions
– Show the influence of dispersal on distribution
New areas
occupied
Figure 50.7
Year
1996
1989
1974
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Species Transplants
• Species transplants
– Include organisms that are intentionally or
accidentally relocated from their original
distribution
– Can often disrupt the communities or
ecosystems to which they have been
introduced
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• Problems with Introduced Species.
– Transplanted species
often explode to
occupy an new area.
• The African honeybee
and Zebra
mussel are good
examples of
this explosion.
Fig. 50.7
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Tens Rule-
Only one out of
ten established
species will
become
common
enough to
become pests
Expansion of
Zebra Mussel
Fig. 50.8
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Behavior and Habitat Selection
• Some organisms
– Do not occupy all of their potential range
• Species distribution
– May be limited by habitat selection behavior
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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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• A specific case of an herbivore limiting
distribution of a food species
EXPERIMENT
W. J. Fletcher tested the effects of two algae-eating animals, sea urchins and limpets, on seaweed
abundance near Sydney, Australia. In areas adjacent to a control site, either the urchins, the limpets, or both were removed.
RESULTS
Fletcher observed a large difference in seaweed growth between areas with and without sea urchins.
100
Sea
urchin
Seaweed cover (%)
80
Both limpets
and urchins
removed
Only
urchins
removed
60
Limpet
40
Only limpets removed
Control (both
urchins and
limpets present)
20
Removing both
limpets and
urchins or
removing only
urchins increased
seaweed cover
dramatically.
Almost no
seaweed grew
in areas where
both urchins and
limpets were
present, or where
only limpets were
removed.
0
August
1982
Figure 50.8
February
1983
August
1983
February
1984
CONCLUSION
Removing both limpets and urchins resulted in the greatest increase of seaweed cover, indicating that both
species have some influence on seaweed distribution. But since removing only urchins greatly increased seaweed growth while
removing only limpets had little effect, Fletcher concluded that sea urchins have a much greater effect than limpets in limiting
seaweed distribution.
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Abiotic Factors
• Abiotic factors that affect the distribution of
organisms may include
– Temperature
– Water
– Sunlight
– Wind
– Rocks and soil
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Temperature
• Environmental temperature
– Is an important factor in the distribution of
organisms because of its effects on biological
processes
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Water
• Water availability among habitats
– Is another important factor in species
distribution
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Sunlight
• Light intensity and quality
– Can affect photosynthesis in ecosystems
• Light
– Is also important to the development and
behavior of organisms sensitive to the
photoperiod
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Wind
• Wind
– Amplifies the effects of temperature on
organisms by increasing heat loss due to
evaporation and convection
– Can change the morphology of plants
Figure 50.9
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Rocks and Soil
• Many characteristics of soil limit the distribution
of plants and thus the animals that feed upon
them
– Physical structure
– pH
– Mineral composition
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Climate
• Climate
– Is the prevailing weather conditions in a
particular area
• Four major abiotic components make up
climate
– Temperature, water, sunlight, and wind
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• Climate patterns can be described on two
scales
– Macroclimate, patterns on the global, regional,
and local level
– Microclimate, very fine patterns, such as those
encountered by the community of organisms
underneath a fallen log
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• Global climate patterns.
– These are largely determined by sunlight and the
planet’s movement in space.
• The sun’s warming effect on the atmosphere,
land, and water establishes the temperature
variations, cycles of air movement, and
evaporation of water that are responsible for
latitudinal variations in climate.
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• Sunlight intensity
– Plays a major part in determining the Earth’s
climate patterns
LALITUDINAL VARIATION IN SUNLIGHT INTENSITY
North Pole
60N
Low angle of incoming sunlight
30N
Tropic of
Cancer
Sunlight directly overhead
0 (equator)
Tropic of
Capricorn
30S
Low angle of incoming sunlight
60S
South pole
Figure 50.10
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Atmosphere
SEASONAL VARIATION IN SUNLIGHT INTENSITY
60N
June solstice: Northern
Hemisphere tilts toward
sun; summer begins in
Northern Hemisphere;
winter begins in
Southern Hemisphere.
30N
0 (equator)
March equinox: Equator faces sun directly;
neither pole tilts toward sun; all regions on Earth
experience 12 hours of daylight and 12 hours of
darkness.
30S
Constant tilt
of 23.5
September equinox: Equator faces sun
directly; neither pole tilts toward sun; all
regions on Earth experience 12 hours of
daylight and 12 hours of darkness.
Figure 50.10
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December solstice: Northern
Hemisphere tilts away from sun;
winter begins in Northern
Hemisphere; summer begins
in Southern Hemisphere.
On February 2, Phil comes out of
his burrow on Gobbler's Knob - in front
of thousands of followers from all over
the world - to predict the weather for
the rest of winter.
According to legend, if
Punxsutawney Phil sees his shadow,
there will be six more weeks of winter
weather. If he does not see his
shadow, there will be an early spring
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• Air circulation and wind patterns
– Play major parts in determining the Earth’s
climate patterns
GLOBAL AIR CIRCULATION AND PRECIPITATION PATTERNS
60N
30N
Descending
dry air
absorbs
moisture
0 (equator)
30S
0
60S
Figure 50.10
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Ascending
moist air
releases
moisture
Descending
dry air
absorbs
moisture
Arid
zone
Tropics
Arid
zone
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GLOBAL WIND PATTERNS
Arctic
Circle
60N
Westerlies
30N
Northeast trades
Doldrums
0
(equator)
Southeast trades
30S
Westerlies
60S
Antarctic
Circle
Figure 50.10
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Regional, Local, and Seasonal Effects on Climate
• Various features of the landscape
– Contribute to local variations in climate
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Mountains
• Mountains have a significant effect on
– The amount of sunlight reaching an area
– Local temperature
– Rainfall
1 As moist air moves in
off the Pacific Ocean and
encounters the westernmost
mountains, it flows upward,
cools at higher altitudes,
and drops a large amount
of water. The world’s tallest
trees, the coastal redwoods,
thrive here.
2 Farther inland, precipitation
increases again as the air
moves up and over higher
mountains. Some of the world’s
deepest snow packs occur here.
3 On the eastern side of the
Sierra Nevada, there is little
precipitation. As a result of
this rain shadow, much of
central Nevada is desert.
Wind
direction
East
Pacific
Ocean
Sierra
Nevada
Coast
Range
Figure 50.12
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Bodies of Water
• Oceans and their currents, and large lakes
– Moderate the climate of nearby terrestrial
environments
2 Air cools at
high elevation.
3 Cooler
air sinks
over water.
4 Cool air over water
moves inland, replacing
rising warm air over land.
Figure 50.11
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1 Warm air
over land rises.
Seasonality
• The angle of the sun
– Leads to many seasonal changes in local
environments
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• Lakes
– Are sensitive to seasonal temperature change
– Experience seasonal turnover
Lake depth (m)
In winter, the coldest water in the lake (0°C) lies just
below the surface ice; water is progressively warmer at
deeper levels of the lake, typically 4–5°C at the bottom.
O2 (mg/L)
0
4
Spring
Winter
8
12
8
16
2
4
4
4
4C
24
O2 concentration
0
Lake depth (m)
1
2 In spring, as the sun melts the ice, the surface water warms to 4°C
and sinks below the cooler layers immediately below, eliminating the
thermal stratification. Spring winds mix the water to great depth,
bringing oxygen (O2) to the bottom waters (see graphs) and
nutrients to the surface.
O2 (mg/L)
0
4 8
12
8
16
4
4
4
4
4
4C
24
High
Medium
O2 (mg/L)
0
4
8
12
8
16
24
Figure 50.13
4
Autumn
4
4
4
4C
4
In autumn, as surface water cools rapidly, it sinks below the
underlying layers, remixing the water until the surface begins
to freeze and the winter temperature profile is reestablished.
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4
Thermocline
3
22
20
18
8
6
5
4C
Summer
Lake depth (m)
Lake depth (m)
Low
O2 (mg/L)
0
4
8
12
8
16
24
In summer, the lake regains a distinctive thermal profile, with
warm surface water separated from cold bottom water by a narrow
vertical zone of rapid temperature change, called a thermocline.
Microclimate
• Microclimate
– Is determined by fine-scale differences in
abiotic factors
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Long-Term Climate Change
• One way to predict future global climate
change
– Is to look back at the changes that occurred
previously
Current
range
Predicted
range
Overlap
Figure 50.14
(a) 4.5C warming over
next century
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(b) 6.5C warming over
next century
• Concept 50.3: Abiotic and biotic factors
influence the structure and dynamics of aquatic
biomes
• Varying combinations of both biotic and abiotic
factors
– Determine the nature of Earth’s many biomes
• Biomes
– Are the major types of ecological associations
that occupy broad geographic regions of land
or water
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• The examination of biomes will begin with
Earth’s aquatic biomes
30N
Tropic of
Cancer
Equator
Tropic of
Capricorn
Continental
shelf
30S
Key
Figure 50.15
Lakes
Rivers
Estuaries
Coral reefs
Oceanic pelagic
zone
Intertidal zone
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Abyssal zone
(below oceanic
pelagic zone)
• Aquatic biomes
– Account for the largest part of the biosphere in
terms of area
– Can contain fresh or salt water
• Oceans
– Cover about 75% of Earth’s surface
– Have an enormous impact on the biosphere
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• Many aquatic biomes
– Are stratified into zones or layers defined by
light penetration, temperature, and depth
Intertidal zone
Neritic zone
Littoral
zone
Limnetic
zone
0
Oceanic zone
Photic zone
200 m
Continental
shelf
Pelagic
zone
Benthic
zone
Photic
zone
Aphotic
zone
Pelagic
zone
Benthic
zone
Aphotic
zone
2,500–6,000 m
Abyssal zone
(deepest regions of ocean floor)
(a) Zonation in a lake. The lake environment is generally classified on the basis
of three physical criteria: light penetration (photic and aphotic zones),
distance from shore and water depth (littoral and limnetic zones), and
whether it is open water (pelagic zone) or bottom (benthic zone).
Figure 50.16a, b
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(b) Marine zonation. Like lakes, the marine environment is generally
classified on the basis of light penetration (photic and aphotic zones),
distance from shore and water depth (intertidal, neritic, and oceanic
zones), and whether it is open water (pelagic zone) or bottom (benthic
and abyssal zones).
• Lakes
– Oligotrophic lakes are deep, nutrient-poor
and do not contain much life.
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Fig. 50.19a
• Eutrophic lakes
are shallower and
have increased
nutrients.
Fig. 50.19b
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• Mesotrophic have a moderate amount of
nutrients and phytoplankton productivity.
– Over long periods of time, oligotrophic lakes
may become mesotrophic as runoff brings in
nutrients.
– Pollution from fertilizers can cause explosions
in algae population and cause a decrease in
oxygen content.
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• Wetlands are areas covered with water that
supports many types of plants.
• They can be saturated or flooded and include areas
known as marshes, bogs, and swamps.
• They are home to
many different
types of organisms,
from herbivores
to crustaceans.
• Unfortunately,
humans have
destroyed them,
but many are now
protected in
many places.
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Fig. 50.21a
Cummings
• Streams and rivers
STREAMS AND RIVERS
– Headwaters are cold and
clear and carry little
sediment and relatively few
mineral nutrients.
– As the stream travels down,
it picks up O2 and nutrients
on the way.
– Nutrient content is largely
determined by the terrain
and vegetation of the area.
– Many streams and rivers
have been polluted by
humans and have caused
many environmental
problems.
A headwater stream in the
Great Smoky Mountains
The Mississippi River far
form its headwaters
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– Estuaries are areas where freshwater and salt water
meet.
• The salinity of these areas can vary greatly.
• They are crucial feeding areas for many types of
water fowl.
Fig. 50.21b
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Intertidal zones are alternately submerged and
exposed by the twice-daily cycle of tides.
They can be rocky or sandy
and provide excellent
examples of
distributional limitations.
Many types of organisms
inhabit these areas,
such as suspension-feeding
worms, crustaceans,
mollusks and others.
These areas are often
by pollution and human activity.
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destroyed
Fig. 50.23a
• Oceanic pelagic biome
• The oceanic pelagic
biome includes most of
the ocean’s water.
OCEANIC PELAGIC BIOME
– The water is
constantly mixed by
ocean currents.
– Plankton live in the
photic zone and are
the producers for this
biome.
17 Open ocean off the island of Hawaii
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– This biome also
includes a great
variety of free
swimming fish and
mammals.
• Coral reefs exist in
the neritic zone.
– They constitute a
conspicuous and
distinctive biome.
– They are
dominated
by coral and
include
a very diverse
assortment of
vertebrates and
invertebrates.
Fig. 50.23b
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• Marine benthic zone
MARINE BENTHIC ZONE
Figure 50.17 A deep-sea hydrothermal vent community
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• Benthos is the ocean bottom below the
neritic and pelagic zones.
– This area is extremely productive due to the
great amount of nutrients found.
– Benthic communities consist of bacteria,
fungi, seaweed and filamentous algae,
numerous invertebrates, and fish.
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• Concept 50.4: Climate largely determines the
distribution and structure of terrestrial biomes
• Climate
– Is particularly important in determining why
particular terrestrial biomes are found in
certain areas
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Climate and Terrestrial Biomes
• Climate has a great impact on the distribution
of organisms, as seen on a climograph
Temperate grassland
Desert
Tropical forest
Annual mean temperature (ºC)
30
Temperate
broadleaf
forest
15
Coniferous
forest
0
Arctic and
alpine
tundra
15
100
Figure 50.18
200
300
Annual mean precipitation (cm)
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400
• The distribution of major terrestrial biomes
30N
Tropic of
Cancer
Equator
Tropic of
Capricorn
30S
Key
Tropical forest
Figure 50.19
Savanna
Desert
Chaparral
Temperate grassland
Temperate broadleaf forest
Coniferous forest
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Tundra
High mountains
Polar ice
General Features of Terrestrial Biomes
• Terrestrial biomes
– Are often named for major physical or climatic
factors and for their predominant vegetation
• Stratification
– Is an important feature of terrestrial biomes
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• Tropical forest
TROPICAL FOREST
Figure 50.20
A tropical rain forest in Borneo
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• Tropical forests are close to the equator,
receive high amounts of rainfall (although this
can vary from region to region), and contain a
great variety of plants and animals.
• The vegetation
is layered, with
the canopy
being one of
the top layers.
Fig. 50.25a
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• Desert
DESERT
Figure 50.20 The Sonoran Desert in southern Arizona
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• Deserts have low rainfall, and are generally hot.
• Vegetation is usually sparse, and includes cacti and
succulents.
• Many animals
are nocturnal,
so they can
avoid the heat.
Fig. 50.25c
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• Savanna
SAVANNA
Figure 50.20
A typical savanna in Kenya
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• Savannas are grasslands with scattered trees, that
show distinct seasons, particularly wet and dry.
– They have many types of plants and animals.
– Fire is an important abiotic factor.
Fig. 50.25b
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• Chaparral
CHAPARRAL
Figure 50.20
An area of chaparral in California
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• Chaparrals have mild wet winters and dry hot
summers.
• They contain
dense spiny,
evergreen
shrubs and
have periodic
fires.
• Some plants
produce seeds
that will only
germinate
after a fire.
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Fig. 50.25d
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• Temperate grassland
TEMPERATE GRASSLAND
Figure 50.20
Sheyenne National Grassland in North Dakota
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• Temperate grasslands exhibit seasonal
drought, occasional fires, and are usually used
for grazing and agriculture.
Fig. 50.25e
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• Coniferous forest
CONIFEROUS FOREST
Rocky Mountain National Park in Colorado
Figure 50.20
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Coniferous forests are the largest terrestrial
biome on earth.
– They exhibit long cold winters and short wet
summers.
– Conifers inhabiting
them are adapted
for the climate.
– Conifer forests
are home to
various animals,
some of which
hibernate.
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Fig. 50.25g
Cummings
• Temperate broadleaf forest
TEMPERATE BROADLEAF FOREST
Figure 50.20
Great Smoky Mountains National Park in North Carolina
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• Temperate deciduous forests contain
dense stands of trees and have very
cold winters and hot summers.
• The trees lose
leaves and go
dormant in winter.
• This biome
includes a large
variety of plants
and animals.
• Humans have
logged many of
these forests around the world.
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Fig. 50.25f
• Tundra
TUNDRA
Figure 50.20
Denali National Park, Alaska, in autumn
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Tundra contains low growing plants.
– The climate is windy and cold which causes a
short growing season.
– A layer of permafrost is found below 1 meter
and does not thaw, which prevents root
growth; not many animals live in tundra
biomes.
– There are two types, arctic, which is found in
areas of Alaska and the Arctic circle, and
alpine, which is found on very high
mountaintops.
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Cummings
Copyright
2002 Pearson
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as Benjamin
Cummings