Download Chapter 50

An Introduction to Ecology
and the Biosphere
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• 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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Organisms and the Environment
• The environment of any organism includes
– Abiotic, or nonliving components
– Biotic, or living components
– All the organisms living in the environment, the
biota
– If you already have these definitions
down don’t worry about copying
them again!
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Subfields of Ecology
• Organismal • Behavioral• Population• Community• Ecosystem• Landscape(The next several slides are to view- don’t worry
about copying them down, but you can add
definitions to this list if you want)
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• But anything on these slides are fair game.. I
may reference “Population ecology” and if you
are unsure of what it means you may have a
hard time answering the questions…
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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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Make sure you know the definition of “population”
• Population ecology
– 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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Try to work on “Summarizing Notes” to save time
• 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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Summarize by cutting out “non-important words”
• Ecosystem ecology
– Energy flow and chemical cycling- among
biotic and abiotic components
) Ecosystem ecology.
What
factors control
photosynthetic
productivity in a
temperate
grassland ecosystem?
(d
Figure 50.3d
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• Landscape ecology– All 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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Precautionary Principle
• The precautionary principle
– Basically states that humans need to be
concerned with how their actions affect the
environment
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BiomesEcologists began to identify broad patterns of
distribution by naming bio-geographic 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
DISTRIBUTION: Biotic Factors
• Biotic factors that affect the distribution of
organisms may include:
– Interactions with other species
– Predation
– Competition
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Abiotic Factors- “The Limiting Factors”
– Temperature
– Water
– Sunlight
– Wind
– Rocks and soil
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Oligotrophic (less life) vs. Eutrophic (more life)
• Lakes
LAKES
Figure 50.17
An oligotrophic lake in
Grand Teton, Wyoming
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A eutrophic lake in Okavango
delta, Botswana
• Wetlands
WETLANDS
Figure 50.17
Okefenokee National Wetland Reserve in Georgia
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• Streams and rivers
STREAMS AND RIVERS
Figure 50.17
A headwater stream in the
Great Smoky Mountains
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The Mississippi River far
form its headwaters
Freshwater and Saltwater meet (Called “Brackish water”)
• Estuaries
ESTUARIES
Figure 50.17 An estuary in a low coastal plain of Georgia
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• Intertidal zones
INTERTIDAL ZONES
Figure 50.17
Rocky intertidal zone on the Oregon coast
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• Oceanic pelagic biome
OCEANIC PELAGIC BIOME
Figure 50.17 Open ocean off the island of Hawaii
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• Coral reefs
CORAL REEFS
Figure 50.17
A coral reef in the Red Sea
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• Marine benthic zone
MARINE BENTHIC ZONE
Figure 50.17 A deep-sea hydrothermal vent community
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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
• Climate (combination of
precipitation and temperature)
has the greatest effect on
distribution of terrestrial (land)
biomes!! As you will see in the next slide…
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• 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
• Tropical forest
TROPICAL FOREST
Figure 50.20
A tropical rain forest in Borneo
Notice how close these regions are to the
equator
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• Desert
DESERT
Figure 50.20
The Sonoran Desert in southern Arizona
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• Savanna
SAVANNA
Figure 50.20
A typical savanna in Kenya
Warm, but has more water than a desert… Not
enough however to be a “tropical rainforest”
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• Chaparral
CHAPARRAL
Figure 50.20
An area of chaparral in California
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• Temperate grassland
TEMPERATE GRASSLAND
Figure 50.20
Sheyenne National Grassland in North Dakota
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• Coniferous forest- trees with needles or needle
like leaves (think christmas trees)
CONIFEROUS FOREST
Rocky Mountain National Park in Colorado
Figure 50.20
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• Temperate broadleaf forest- leaves change
color and drop in the fall (known as Deciduous
trees).
TEMPERATE BROADLEAF FOREST
Figure 50.20
Great Smoky Mountains National Park in North Carolina
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• Tundra- has a layer of permafrost- permanently
frozen soil, it doesn’t get warm enough here to
melt
TUNDRA
Figure 50.20
Denali National Park, Alaska, in autumn
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Behavioral Ecology
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
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Ethology
• Ethology is the scientific study of animal
behavior
– Particularly in natural environments
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Imprinting-not all animals do this.
• Imprinting is a type of behavior
– That includes both learning and innate
components and is generally irreversible
• Konrad Lorenz showed that
– When baby geese spent the first few
hours of their life with him, they
imprinted on him as their parent
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An example where cranes have imprinted on a
person, then followed them into adulthood to
safe breeding grounds.
• Conservation biologists have taken advantage
of imprinting
– In programs to save the whooping crane from
extinction
Figure 51.6
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Genetics and Behavior
Many behaviors have a strong genetic
component
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• A kinesis
– Is a simple change in activity or turning rate in
response to a stimulus
• A taxis
– Is a more or less automatic, oriented
movement toward or away from a stimulus
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An example of Kinesis
• Sow bugs
– Become more active in dry areas and less
active in humid areas
Moist site
under leaf
Dry open
area
(a) Kinesis increases the chance that a sow bug will encounter and
stay in a moist environment.
Figure 51.7a
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An example of Taxis
• Many stream fish exhibit positive rheotaxis
– Where they automatically swim in an upstream
direction.
Direction
of river
current
(b) Positive rheotaxis keeps trout facing into the current, the direction
from which most food comes.
Figure 51.7b
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Migration
• Many features of migratory behavior in birds
– Have been found to be genetically
programmed
Figure 51.8
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Animal Communication and Signal Behavior
• Animals communicate using
– Visual, auditory, chemical(smell/pheromones),
tactile(touch), and electrical signals
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Conditioning- Learned behavior
• Operant conditioning is another type of
associative learning
– In which an animal learns to associate one of
its behaviors with a reward or punishment
Figure 51.16
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Mating Systems and Mate Choice
• The mating relationship between males and
females
– Varies a great deal from species to species
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Mating behavior
• In many species, mating is promiscuous
– With no strong pair-bonds or lasting
relationships
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• In monogamous relationships
– One male mates with one female
(a) Since monogamous species, such as these trumpeter swans, are
often monomorphic, males and females are difficult to distinguish
using external characteristics only.
Figure 51.25a
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• In polyandrous systems
– One female mates with many males
– The females are often more showy than the males
Figure 51.25c
(c) In polyandrous species, such as these Wilson’s phalaropes, females
(top) are generally more ornamented than males.
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What determines mating behavior?
• The needs of the young
– Are an important factor constraining the
evolution of mating systems
• The certainty of paternity
– Influences parental care and mating behavior
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Parental Care is important!
• In species that produce large numbers of
offspring
– Parental care is at least as likely to be carried
out by males as females (fish with eggs in
mouth) Egg Brooding.
Eggs
Figure 51.26
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Mate choice
• Mate Choice by Females
• Male zebra finches
– Are more ornate than females, a trait that may
affect mate choice by the females
Figure 51.27
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Competition to pass on genes!
• Such competition may involve agonistic
behavior.
– An often ritualized contest that determines
which competitor gains access to a resource
Figure 51.30
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Altruism (selflessness)
• On occasion, some animals
– Behave in ways that reduce their individual
fitness but increase the fitness of others
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Population Ecology
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
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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Types of Dispersion
• A clumped dispersion
– Is one in which individuals aggregate in
patches
– May be influenced by resource availability and
behavior
(a) Clumped. For many animals, such as these wolves, living
in groups increases the effectiveness of hunting, spreads
the work of protecting and caring for young, and helps
exclude other individuals from their territory.
Figure 52.3a
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• A uniform dispersion
– Is one in which individuals are evenly
distributed
– May be influenced by social interactions such
as territoriality
(b) Uniform. Birds nesting on small islands, such as these
king penguins on South Georgia Island in the South
Atlantic Ocean, often exhibit uniform spacing, maintained
by aggressive interactions between neighbors.
Figure 52.3b
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• A random dispersion
– Is one in which the position of each individual
is independent of other individuals
(c) Random. Dandelions grow from windblown seeds that
land at random and later germinate.
Figure 52.3c
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Survivorship Curves- When do animals die off?
Some species are more likely to die while young
(like salmon), Some species are more likely to
die in old age (like elephants), for some
species it doesn’t matter, they are just as likely
to die as babies or as adults (like squirrels).
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Survivorship Curves- When do animals die off?
• Survivorship curves can be classified into three
general types
Number of survivors (log scale)
– Type I, Type II, and Type III
1,000
I
100
II
10
III
1
0
Figure 52.5
50
Percentage of maximum life span
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100
R selected species- Reproduce a single time and die
• Species that exhibit “big-bang” reproduction
– Reproduce a single time and die. Make a lot of
babies!
Figure 52.6
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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
(a) Most weedy plants, such as this dandelion, grow quickly and
produce a large number of seeds, ensuring that at least some
will grow into plants and eventually produce seeds themselves.
Figure 52.8a
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Exponential Growth
• Exponential population growth
– Is population increase under idealized
conditions.
• Ideal Conditions- unlimited resources, no
predators or competition!
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Under Ideal Conditions
• Exponential population growth
– Results in a J-shaped curve
2,000
dN
dt
1.0N
Population size (N)
1,500
dN
dt
0.5N
1,000
500
0
0
Figure 52.9
10
5
Number of generations
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15
• The J-shaped curve of exponential growth
– Is characteristic of some populations that are
rebounding
Elephant population
8,000
6,000
4,000
2,000
0
1900
1920
Figure 52.10
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1940
Year
1960
1980
• Carrying capacity (K)
– Is the maximum population size the
environment can support
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Logistic Growth- S shaped curve with Carrying Capacity
• The logistic model of population growth
– Produces a sigmoid (S-shaped) curve
2,000
Population size (N)
dN
dt
1.0N
1,500
K
Exponential
growth
1,500
Logistic growth
1,000
dN
dt
1.0N
1,500 N
1,500
500
0
0
Figure 52.12
5
10
Number of generations
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15
Selection Strategies:
• K-selection (elephants, humans…)
– Selects for life history traits that are sensitive
to population density. Have a lot of parental
care!
• r-selection (mice, insects, dandelions)
– Selects for life history traits that maximize
reproduction. None, or little parental care.
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• Populations are regulated by a complex
interaction of biotic and abiotic influences
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Competition for Resources
• In crowded populations, increasing population
density increases competition for resources!
4.0
3.8
Average clutch size
Average number of seeds
per reproducing individual
(log scale)
10,000
1,000
100
3.6
3.4
3.2
3.0
2.8
0
0
10
0
100
Seeds planted per m2
(a) Plantain. The number of seeds
produced by plantain (Plantago major)
decreases as density increases.
10
20
30
40
50
60
70
Density of females
(b) Song sparrow. Clutch size in the song sparrow
on Mandarte Island, British Columbia, decreases
as density increases and food is in short supply.
Figure 52.15a,b
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80
Territorial
• Cheetahs are highly territorial
– Using chemical communication to warn other
cheetahs of their boundaries
Figure 52.16
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• Oceanic birds
– Exhibit territoriality in nesting behavior
Figure 52.17
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Health• Population density: can influence the health
and survival of organisms.
• For Example: In dense populations pathogens
and disease can spread more rapidly!
Figure right: Black
Plague spread
quickly in places
where there were a
lot of people (high
population density)
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Population instability:
• Extreme fluctuations in population size
Commercial catch (kg) of
male crabs (log scale)
– Are typically more common in invertebrates
(like crabs, and insects) than in large
mammals
730,000
100,000
10,000
1950
Figure 52.19
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1960
1970
Year
1980
1990
Population Cycles- Predator/Prey Relationships
160
Snowshoe hare
120
Lynx
9
80
6
40
3
0
1850
0
1875
Figure 52.21
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1900
Year
1925
Lynx population size
(thousands)
Hare population size
(thousands)
• Many populations undergo regular boom-and-bust cycles.
• Human population growth has slowed after
centuries of exponential increase
• 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
5
4
3
2
The Plague
1
Figure 52.22
8000
B.C.
4000
B.C.
3000
B.C.
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2000
B.C.
1000
B.C.
0
1000
A.D.
0
2000
A.D.
Human population (billions)
6
Comparing Ages of Different Nations:
• Age structure
– Is commonly represented in pyramids
Rapid growth
Afghanistan
Male
Female
8 6 4 2 0 2 4 6 8
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
Slow growth
United States
Female
Male
8 6 4 2 0 2 4 6 8
Percent of population
Figure 52.25
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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
Decrease
Italy
Female
Male
8 6 4 2 0 2 4 6 8
Percent of population
Infant Mortality and Life Expectancy
• Infant mortality and life expectancy at birth
– Vary widely among developed and developing
countries
80
50
Life expectancy (years)
Infant mortality (deaths per 1,000 births)
60
40
30
20
40
20
10
0
0
Developed
countries
Figure 52.26
60
Developing
countries
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Developed
countries
Developing
countries
Ecological Footprint
• The ecological footprint concept
– Summarizes the total amount of land and
water area needed to sustain the people of a
nation
– Is one measure of how close we are to the
carrying capacity of Earth
Check out myfootprint.org
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Do this!
Check out myfootprint.org
Take the quiz online to find
your footprint!
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• Ecological footprints for 13 countries
Ecological footprint (ha per person)
– Show that the countries vary greatly in their footprint
size and their available ecological capacity
16
14
12
New Zealand
10
USA
Germany
Japan Netherlands
Norway
8
6
UK
Spain
4
World
China
India
2
0
Australia
Canada
Sweden
0
2
4
6
8
10
12
Available ecological
capacity (ha per person)
Figure 52.27
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14
16
Community Ecology
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
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Community Interactions• Include: competition, predation, herbivory,
symbiosis, and disease
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• Interactions:
– Can have differing effects on the populations
involved
Table 53.1
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Ecological Niches
• The ecological niche: an organisms “role”
• Is the total of an organism’s use of the biotic
and abiotic resources in its environment
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Can 2 organisms with the same “niche” co-exist?
• YES!
– If there are one or more significant difference
in their niches
EXPERIMENT
Ecologist Joseph Connell studied two barnacle
species Balanus balanoides and Chthamalus stellatus that have a
stratified distribution on rocks along the coast of Scotland.
RESULTS
When Connell removed Balanus from the lower
strata, the Chthamalus population spread into that area.
High tide
High tide
Chthamalus
Chthamalus
realized niche
Balanus
Chthamalus
fundamental niche
Balanus
realized niche
Ocean
Figure 53.2
Low tide
In nature, Balanus fails to survive high on the rocks because it is
unable to resist desiccation (drying out) during low tides. Its realized niche
is therefore similar to its fundamental niche. In contrast, Chthamalus is
usually concentrated on the upper strata of rocks. To determine the
fundamental of niche of Chthamalus, Connell removed Balanus from the
lower strata.
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Ocean
Low tide
CONCLUSION
The spread of Chthamalus when Balanus was removed
indicates that competitive exclusion makes the realized
niche of Chthamalus much smaller than its fundamental niche.
How is that possible?
Wouldn’t one just
outcompete the other
to extinction?
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Resource Partitioning
• Resource partitioning is the differentiation of
niches
– That enables similar species to coexist in a
community
A. insolitus
usually perches
on shady branches.
A. ricordii
A. distichus perches
on fence posts and
other sunny
surfaces.
A. insolitus
A. alinigar
A. christophei
A. distichus
A. cybotes
A. etheridgei
Figure 53.3
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• Feeding adaptations of predators include
– Claws, teeth, fangs, stingers, and poison
• Animals also display
– A great variety of defensive adaptations
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• Cryptic coloration, or camouflage
– Makes prey difficult to spot
Figure 53.5
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• Aposematic coloration
– Warns predators to stay away from prey
Figure 53.6
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2 types of Mimicry:
• In Batesian mimicry
– A palatable (edible) or harmless species
mimics an unpalatable (inedible) or harmful
model
(b) Green parrot snake
Figure 53.7a, b
(a) Hawkmoth larva
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• In Müllerian mimicry
– Two or more unpalatable species resemble
each other
(a) Cuckoo bee
Figure 53.8a, b
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(b) Yellow jacket
Herbivory
• Herbivory, the process in which an herbivore
eats parts of a plant
– Has led to the evolution of plant mechanical
and chemical defenses and consequent
adaptations by herbivores
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Parasitism
• In parasitism, one organism, the parasite
– Takes nourishment from another organism (a
host), which is harmed in the process.
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Mutualism
• Mutualistic symbiosis, or mutualism
– Benefits both species
Figure 53.9
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Commensalism
• In commensalism
– One species benefits and the other is not
affected
Figure 53.10
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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
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• Two different communities can have the same
species richness, but a different relative
abundance
A
B
C
D
Community 1
Figure 53.11
A: 25%
B: 25%
A: 80%
Community 2
B: 5%
C: 5%
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C: 25%
D: 25%
D: 10%
Trophic Structure
• Trophic structure
– Is the feeding relationships between organisms
in a community
– Is a key factor in community dynamics
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Food Chains
• Food chains
– Link the trophic
levels from
producers to top
carnivores
Quaternary
consumers
Carnivore
Carnivore
Tertiary
consumers
Carnivore
Carnivore
Secondary
consumers
Carnivore
Carnivore
Primary
consumers
Zooplankton
Herbivore
Primary
producers
Plant
Figure 53.12
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A terrestrial food chain
Phytoplankton
A marine food chain
Food Webs
• A food web
Humans
– Is a branching
food chain with
complex
trophic
interactions
Smaller toothed
whales
Baleen
whales
Crab-eater seals
Birds
Sperm
whales
Elephant
seals
Leopard
seals
Fishes
Squids
Carnivorous
plankton
Copepods
Euphausids
(krill)
Phytoplankton
Figure 53.13
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Keystone Species
• Keystone species
– Have strong roles in the ecosystem. When
removed can have catastrophic effects.
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An example of a keystone species
• Field studies of sea stars
Number of species
present
– Exhibit their role as a keystone species in intertidal
communities
20
With Pisaster (control)
15
10
Without Pisaster (experimental)
5
0
1963 ´64 ´65 ´66 ´67 ´68 ´69 ´70 ´71 ´72 ´73
(a) The sea star Pisaster ochraceous feeds
preferentially on mussels but will
consume other invertebrates.
Figure 53.16a,b
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(b) When Pisaster was removed from an intertidal zone,
mussels eventually took over the rock face and eliminated
most other invertebrates and algae. In a control area from
which Pisaster was not removed, there was little change
in species diversity.
Another Keystone species
• Observation of sea otter populations and their
predation
Otter number
(% max. count)
80
60
40
20
0
(a) Sea otter abundance
400
Grams per
0.25 m2
– Shows the
effect the
otters have
on ocean
communities
100
300
200
100
0
Number per
0.25 m2
(b) Sea urchin biomass
10
8
6
4
2
0
1972
1985
1989
1993
1997
Year
Figure 53.17
Food chain before
killer whale involvement in chain
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(c) Total kelp density
Food chain after killer
whales started preying
on otters
Yet another example:
• Beaver dams
– Can transform landscapes on a very large
scale
Figure 53.18
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What Is Disturbance?
• A disturbance
– Is an event that changes a community
– Removes organisms from a community
– Alters resource availability
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Examples of Disturbances
• Fire
– Is a significant disturbance in most terrestrial
ecosystems
– Is often a necessity in some communities
Figure 53.21a–c
(a) Before a controlled burn.
A prairie that has not burned for
several years has a high proportion of detritus (dead grass).
(b) During the burn. The detritus
serves as fuel for fires.
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(c) After the burn. Approximately one
month after the controlled burn,
virtually all of the biomass in this
prairie is living.
• The large-scale fire in Yellowstone National
Park in 1988
– Demonstrated that communities can often
respond very rapidly to a massive disturbance
(a) Soon after fire. As this photo taken soon after the fire shows,
the burn left a patchy landscape. Note the unburned trees in the
distance.
Figure 53.22a, b
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( b) One year after fire. This photo of the same general area taken the
following year indicates how rapidly the community began to
recover. A variety of herbaceous plants, different from those in the
former forest, cover the ground.
Ecological Succession
• Ecological succession
– Is the sequence of community and ecosystem
changes after a disturbance
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Ecological Succession
• Ecological succession
– Is the sequence of community and ecosystem
changes after a disturbance
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• 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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Pioneer Species
• Early-arriving species
– May facilitate the appearance of later species
by making the environment more favorable
– May inhibit establishment of later species
– May tolerate later species but have no impact
on their establishment
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An example of a study site for succession:
• Retreating glaciers
– Provide a valuable field-research opportunity on
succession
Canada
Grand
Pacific Gl.
1940
Alaska
0
1912
1948
1879
1949
1935
Miles
1941
1 899
1907
5
1879
1948
1931
1911
1900
1892
1879
1913
1860
Reid Gl.
Johns Hopkins
Gl.
1879
Glacier
Bay
1830
1780
1760
Pleasant Is.
Figure 53.23
McBride glacier retreating
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10
• Succession on the moraines in Glacier Bay, Alaska
– Follows a predictable pattern of change in vegetation
and soil characteristics
(a) Pioneer stage, with fireweed dominant
(b) Dryas stage
60
Soil nitrogen (g/m2)
50
40
30
20
10
0
Figure 53.24a–d
Pioneer Dryas Alder Spruce
Successional stage
(d) Nitrogen fixation by Dryas and alder
increases the soil nitrogen content.
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(c) Spruce stage
Ecosystems
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
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TWO MAIN PROCESSES:
• Energy Flow and Chemical Cycling
• 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 54.1: Ecosystem ecology emphasizes
energy flow and chemical cycling
• Ecosystems are Transformers of energy and
processors of matter.
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Trophic Relationships
• Energy flows through an ecosystem
– Entering as light and exiting as heat
Tertiary
consumers
Microorganisms
and other
detritivores
Detritus
Secondary
consumers
Primary consumers
Primary producers
Heat
Key
Chemical cycling
Energy flow
Figure 54.2
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Sun
Decomposition- connects all trophic levels
• Detritivores, mainly bacteria and fungi, recycle
essential chemical elements
– By decomposing organic material and returning
elements to inorganic reservoirs
Figure 54.3
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Limits to primary productivity
• Concept 54.2: Physical and chemical factors
limit primary production in ecosystems
• Primary production in an ecosystem is the
amount of light energy converted to chemical
energy by autotrophs during a given time
period- basically, the energy produced by
photosynthesis
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Only a small fraction of solar energy actually
strikes photosynthetic organisms
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Terrestrial ecosystems vs. Marine Ecosystems
• Terrestrial ecosystems contribute about twothirds of global Primary Productivity
• Marine ecosystems about one-third
North Pole
60 N
30 N
Equator
30 S
60 S
South Pole
180
120 W
60 W
Figure 54.5
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0
60 E
120 E
180
What are limiting factors to primary productivity?
Terrestrial
Ecosystems
Temperature
Precipitation
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Aquatic
Ecosystems
Nutrients
Light
available
Primary Production in Marine and Freshwater
Ecosystems- Limiting Factors
• In marine and freshwater ecosystems, both
light and nutrients are important in controlling
primary production
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Light Limitation
• The depth of light penetration, affects primary
production throughout the photic zone of an
ocean or lake.
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Nutrient Limitation
• More than light, nutrients limit primary
production
• Nitrogen and phosphorous are typically the
nutrients that most often limit marine
production
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What happens if there are too many nutrients?
• In some areas, sewage runoff
– Has caused eutrophication of lakes, which can
lead to the eventual loss of most fish species from
the lakes
Figure 54.7
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Terrestrial and Wetland Ecosystems- Primary
Production
• In terrestrial and wetland ecosystems climatic
factors, such as temperature and moisture,
affect primary production on a large geographic
scale
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Trophic Efficiency and Ecological Pyramids
• Trophic efficiency
– Is the percentage of production transferred
from one trophic level to the next
– Usually ranges from 5% to 20%
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Production Efficiency
• When a caterpillar feeds on a plant leaf
– Only about one-sixth of the energy in the leaf
is used for secondary production
Plant material
eaten by caterpillar
200 J
67 J
Feces
100 J
33 J
Figure 54.10
Growth (new biomass)
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Cellular
respiration
Pyramids of Production
• This loss of energy with each transfer in a food chain
– Can be represented by a pyramid of net production
Tertiary
consumers
Secondary
consumers
Primary
consumers
Primary
producers
Figure 54.11
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10 J
100 J
1,000 J
10,000 J
1,000,000 J of sunlight
• Most biomass pyramids
– Show a sharp decrease at successively higher
trophic levels
Trophic level
Dry weight
(g/m2)
Tertiary consumers
1.5
Secondary consumers
11
Primary consumers
Primary producers
(a) Most biomass pyramids show a sharp decrease in biomass at
successively higher trophic levels, as illustrated by data from
a bog at Silver Springs, Florida.
Figure 54.12a
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37
809
Energy Flow through Ecosystems: Inefficiency
• Eating meat is a relatively inefficient way of
tapping photosynthetic production.
• Worldwide agriculture could sustain many more
people, If humans all ate only plant material.
Trophic level
Secondary
consumers
Primary
consumers
Primary
producers
Figure 54.14
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Nutrient circuits that cycle matter through an
ecosystem
• Concept 54.4: Biological and geochemical
processes move nutrients between organic and
inorganic parts of the ecosystem
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Biogeochemical Cycles
• The water cycle and the carbon cycle
THE CARBON CYCLE
THE WATER CYCLE
CO2 in atmosphere
Transport
over land
Photosynthesis
Solar energy
Cellular
respiration
Net movement of
water vapor by wind
Precipitation
over ocean
Evaporation
from ocean
Precipitation
over land
Burning of
fossil fuels
and wood
Evapotranspiration
from land
Percolation
through
soil
Runoff and
groundwater
Figure 54.17
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Carbon compounds
in water
Higher-level
Primary consumers
consumers
Detritus
Decomposition
Larger scale processess- water and carbon cycle
• Water moves in a global cycle, driven by solar
energy
• The carbon cycle reflects the process between
photosynthesis and cellular respiration
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• The nitrogen cycle and the phosphorous cycle
THE PHOSPHORUS CYCLE
THE NITROGEN CYCLE
N2 in atmosphere
Rain
Geologic
uplift
Runoff
Assimilation
NO3
Nitrogen-fixing
bacteria in root
nodules of legumes
Plants
Weathering
of rocks
Denitrifying
bacteria
Consumption
Sedimentation
Decomposers
Ammonification
NH3
Nitrogen-fixing
soil bacteria
Nitrifying
bacteria
Nitrification
Soil
Plant uptake
of PO43
Leaching
NO2
NH4+
Nitrifying
bacteria
Figure 54.17
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Decomposition
Local processess- Nitrogen and Phosphorus cycles
• Most of the nitrogen cycling in natural
ecosystems involves local cycles between
organisms and soil or water
• The phosphorus cycle is relatively localized
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Decomposition and Nutrient Cycling Rates
• Decomposers (detritivores) play a key role in
the general pattern of chemical cycling
Consumers
Producers
Decomposers
Nutrients
available
to producers
Abiotic
reservoir
Figure 54.18
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Geologic
processes
Acid Precipitation- From combustion of fossil fuels
• North American and European ecosystems
downwind from industrial regions
– Have been damaged by rain and snow containing
nitric and sulfuric acid
4.6
4.3
4.6
4.3
4.6
4.1
4.3
4.6
Europe
Figure 54.21
North America
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• By the year 2000
– The entire contiguous United States was affected by
acid precipitation
Figure 54.22
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Field pH
5.3
5.2–5.3
5.1–5.2
5.0–5.1
4.9–5.0
4.8–4.9
4.7–4.8
4.6–4.7
4.5–4.6
4.4–4.5
4.3–4.4
4.3
Toxins in the Environment
• Humans release an immense variety of toxic
chemicals
• One of the reasons such toxins are so harmful
– Is that they become more concentrated in
trophic levels of a food web
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biological magnification
Toxins concentrate at higher trophic levels because
at these levels biomass tends to be lower
Concentration of PCBs
Herring
gull eggs
124 ppm
Lake trout
4.83 ppm
Smelt
1.04 ppm
Figure 54.23
Zooplankton
0.123 ppm
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Phytoplankton
0.025 ppm