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Chapter 51 Animal Behavior.

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1 Chapter 51 Animal Behavior

2 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

3 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

4 Behavioral ecology is the study of the ecological and evolutionary basis for animal behavior
It integrates proximate and ultimate explanations for animal behavior

5 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

6 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

7 Fig. 51-3 (a) Figure 51.3 Sign stimuli in a classic fixed action pattern (b)

8 Oriented Movement Environmental cues can trigger movement in a particular direction

9 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

10 Moist site under leaf Dry open area Sow bug Fig. 51-4
Figure 51.4 A kinesis

11 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

12 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

13 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

14 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

15 (a) Worker bees (b) Round dance (food near) (c) Waggle dance
Fig. 51-8 (a) Worker bees (b) Round dance (food near) (c) Waggle dance (food distant) A 30° Figure 51.8 Honeybee dance language C B Beehive 30° Location A Location B Location C

16 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

17 (a) Minnows before alarm (b) Minnows after alarm Fig. 51-9
Figure 51.9 Minnows responding to the presence of an alarm substance

18 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

19 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

20 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

21 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

22 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

23 Fig (a) Konrad Lorenz and geese Figure Imprinting (b) Pilot and cranes

24 Video: Bee Pollinating
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

25 EXPERIMENT Nest Pinecone RESULTS Nest No nest Fig. 51-11
Figure Does a digger wasp use landmarks to find her nest? Nest No nest

26 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

27 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

28 It is also called trial-and-error learning
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

29 Fig Figure Operant conditioning

30 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

31 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

32 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 low-density populations benefit from short-distance foraging

33 Natural selection favors different foraging behavior depending on the density of the population

34 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

35 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

36 Researchers determined experimentally that the total flight height (which reflects total energy expenditure) was minimized at a drop height of 5 m The average flight height for crows is 5.2 m

37 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

38 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

39 Consider bird species where chicks need a continuous supply of food
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)

40 Certainty of paternity influences parental care and mating behavior
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

41 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

42 An Introduction to Ecology and the Biosphere
Chapter 52 An Introduction to Ecology and the Biosphere

43 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

44 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

45 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

46 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

47 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

48 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

49 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

50 Ecologists consider multiple factors when attempting to explain the distribution of species

51 Figure 52.6 Flowchart of factors limiting geographic distribution
Why is species X absent from an area? Yes Area inaccessible or insufficient time Yes Does dispersal limit its distribution? Habitat selection Yes Predation, parasitism, competition, disease Does behavior limit its distribution? Chemical factors No Do biotic factors (other species) limit its distribution? Water Oxygen Salinity pH Soil nutrients, etc. No Do abiotic factors limit its distribution? No Temperature Light Soil structure Fire Moisture, etc. Physical factors Figure 52.6 Flowchart of factors limiting geographic distribution

52 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

53 Biotic factors that affect the distribution of organisms may include:
Interactions with other species Predation Competition

54 Abiotic factors affecting distribution of organisms include:
Temperature Water Sunlight Wind Rocks and soil Most abiotic factors vary in space and time

55 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

56 Water Water availability in habitats is another important factor in species distribution Desert organisms exhibit adaptations for water conservation

57 Salinity Salt concentration affects water balance of organisms through osmosis Few terrestrial organisms are adapted to high-salinity habitats

58 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

59 Rocks and Soil Many characteristics of soil limit distribution of plants and thus the animals that feed upon them: Physical structure pH Mineral composition

60 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

61 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

62 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

63 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

64 Aquatic Biomes Major aquatic biomes can be characterized by their physical environment, chemical environment, geological features, photosynthetic organisms, and heterotrophs

65 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

66 Tropical forest Savanna Desert Chaparral 30ºN Tropic of Temperate
Fig Tropical forest Savanna Desert Chaparral 30ºN Tropic of Cancer Temperate grassland Equator Temperate broadleaf forest Tropic of Capricorn Northern coniferous forest 30ºS Tundra Figure The distribution of major terrestrial biomes High mountains Polar ice

67 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

68 Terrestrial Biomes Terrestrial biomes can be characterized by distribution, precipitation, temperature, plants, and animals

69 Chapter 53 Population Ecology

70 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

71 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

72 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

73 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

74 Patterns of Dispersion
Environmental and social factors influence spacing of individuals in a population

75 Fig. 53-4 (a) Clumped (b) Uniform Figure 53.4 Patterns of dispersion within a population’s geographic range (c) Random

76 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

77 Number of survivors (log scale)
Fig. 53-6 1,000 I 100 II Number of survivors (log scale) 10 Figure 53.6 Idealized survivorship curves: Types I, II, and III III 1 50 100 Percentage of maximum life span

78 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

79 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

80 Fig. 53-7 Figure 53.7 An agave (Agave americana), an example of big-bang reproduction

81 “Trade-offs” and Life Histories
Organisms have finite resources, which may lead to trade-offs between survival and reproduction

82 Some plants produce a large number of small seeds, ensuring that at least some of them will grow and eventually reproduce

83 Fig. 53-9a Figure 53.9a Variation in the size of seed crops in plants (a) Dandelion

84 Other types of plants produce a moderate number of large seeds that provide a large store of energy that will help seedlings become established

85 Fig. 53-9b Figure 53.9b Variation in the size of seed crops in plants (b) Coconut palm

86 In animals, parental care of smaller broods may facilitate survival of offspring

87 Fig. 53-8 RESULTS 100 Male Female 80 60 Parents surviving the following winter (%) 40 Figure 53.8 How does caring for offspring affect parental survival in kestrels? 20 Reduced brood size Normal brood size Enlarged brood size

88 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

89 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

90 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

91 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

92 Equation of exponential population growth:
dN dt rmaxN

93 Exponential population growth results in a J-shaped curve

94 2,000 = 1.0N 1,500 = 0.5N Population size (N) 1,000 500 5 10 15
Fig 2,000 dN = 1.0N dt 1,500 dN = 0.5N dt Population size (N) 1,000 500 Figure Population growth predicted by the exponential model 5 10 15 Number of generations

95 The J-shaped curve of exponential growth characterizes some rebounding populations

96 Fig 8,000 6,000 Elephant population 4,000 2,000 Figure Exponential growth in the African elephant population of Kruger National Park, South Africa 1900 1920 1940 1960 1980 Year

97 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

98 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 dN dt (K  N) K rmax N

99 Table 53-3 Table 53.3

100 The logistic model of population growth produces a sigmoid (S-shaped) curve

101 Exponential growth 2,000 = 1.0N 1,500 K = 1,500 Population size (N)
Fig Exponential growth 2,000 dN = 1.0N dt 1,500 K = 1,500 Population size (N) Logistic growth 1,000 dN 1,500 – N = 1.0N dt 1,500 Figure Population growth predicted by the logistic model 500 5 10 15 Number of generations

102 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

103 Number of Paramecium/mL
Fig 1,000 180 150 800 120 Number of Paramecium/mL 600 Number of Daphnia/50 mL 90 400 60 200 30 Figure How well do these populations fit the logistic growth model? 5 10 15 20 40 60 80 100 120 140 160 Time (days) Time (days) (a) A Paramecium population in the lab (b) A Daphnia population in the lab

104 Number of Paramecium/mL
Fig a 1,000 800 Number of Paramecium/mL 600 400 200 Figure 53.13a How well do these populations fit the logistic growth model? 5 10 15 Time (days) (a) A Paramecium population in the lab

105 Some populations overshoot K before settling down to a relatively stable density

106 (b) A Daphnia population in the lab
Fig b 180 150 120 Number of Daphnia/50 mL 90 60 30 Figure 53.13b How well do these populations fit the logistic growth model? 20 40 60 80 100 120 140 160 Time (days) (b) A Daphnia population in the lab

107 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

108 There are two general questions about regulation of population growth:
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?

109 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

110 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

111 Competition for Resources
In crowded populations, increasing population density intensifies competition for resources and results in a lower birth rate

112 Percentage of juveniles producing lambs
Fig 100 80 60 Percentage of juveniles producing lambs 40 Figure Decreased reproduction at high population densities 20 200 300 400 500 600 Population size

113 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

114 Disease Population density can influence the health and survival of organisms In dense populations, pathogens can spread more rapidly

115 Predation As a prey population builds up, predators may feed preferentially on that species

116 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.

117 Intrinsic Factors For some populations, intrinsic (physiological) factors appear to regulate population size

118 Population Dynamics The study of population dynamics focuses on the complex interactions between biotic and abiotic factors that cause variation in population size

119 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

120 Fig 2,100 1,900 1,700 1,500 Number of sheep 1,300 1,100 900 Figure Variation in size of the Soay sheep population on Hirta Island, 1955–2002 700 500 1955 1965 1975 1985 1995 2005 Year

121 Changes in predation pressure can drive population fluctuations

122 50 2,500 Wolves Moose 40 2,000 30 1,500 Number of wolves
Fig 50 2,500 Wolves Moose 40 2,000 30 1,500 Number of wolves Number of moose 20 1,000 10 500 Figure Fluctuations in moose and wolf populations on Isle Royale, 1959–2006 1955 1965 1975 1985 1995 2005 Year

123 Population Cycles: Scientific Inquiry
Some populations undergo regular boom-and-bust cycles Lynx populations follow the 10 year boom-and-bust cycle of hare populations Three hypotheses have been proposed to explain the hare’s 10-year interval

124 Number of hares (thousands) Number of lynx (thousands)
Fig Snowshoe hare 160 120 9 Figure Population cycles in the snowshoe hare and lynx Lynx Number of hares (thousands) Number of lynx (thousands) 80 6 40 3 1850 1875 1900 1925 Year

125 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

126 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

127 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

128 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

129 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

130 The Global Human Population
The human population increased relatively slowly until about 1650 and then began to grow exponentially

131 7 6 5 4 3 2 1 Human population (billions) The Plague 8000 B.C.E. 4000
Fig 7 6 5 4 Human population (billions) 3 2 The Plague Figure Human population growth (data as of 2006) 1 8000 B.C.E. 4000 B.C.E. 3000 B.C.E. 2000 B.C.E. 1000 B.C.E. 1000 C.E. 2000 C.E.

132 Though the global population is still growing, the rate of growth began to slow during the 1960s

133 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

134 Rapid growth Slow growth No growth Afghanistan United States Italy
Fig Rapid growth Slow growth No growth Afghanistan United States Italy Male Female Age Male Female Age Male Female 85+ 85+ 80–84 80–84 75–79 75–79 70–74 70–74 65–69 65–69 60–64 60–64 55–59 55–59 50–54 50–54 45–49 45–49 40–44 40–44 35–39 35–39 30–34 30–34 25–29 25–29 20–24 20–24 Figure Age-structure pyramids for the human population of three countries (data as of 2005) 15–19 15–19 10–14 10–14 5–9 5–9 0–4 0–4 10  8 6 4 2 2 4 6 8 10  8 6 4 2 2 4 6 8 8 6 4 2 2 4 6 8 Percent of population Percent of population Percent of population

135 Age structure diagrams can predict a population’s growth trends
They can illuminate social conditions and help us plan for the future

136 Global Carrying Capacity
How many humans can the biosphere support?

137 Estimates of Carrying Capacity
The carrying capacity of Earth for humans is uncertain The average estimate is 10–15 billion

138 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

139 13.4 9.8 5.8 Not analyzed Log (g carbon/year) Fig. 53-27
Figure The amount of photosynthetic products that humans use around the world 5.8 Not analyzed

140 Our carrying capacity could potentially be limited by food, space, nonrenewable resources, or buildup of wastes

141 Chapter 54 Community Ecology

142 Overview: A Sense of Community
A biological community is an assemblage of populations of various species living close enough for potential interaction

143 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)

144 Competition Interspecific competition (–/– interaction) occurs when species compete for a resource in short supply

145 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

146 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

147 Resource partitioning is differentiation of ecological niches, enabling similar species to coexist in a community

148 A. distichus perches on fence posts and other sunny surfaces.
Fig. 54-2 A. distichus perches on fence posts and other sunny surfaces. A. insolitus usually perches on shady branches. A. ricordii Figure 54.2 Resource partitioning among Dominican Republic lizards A. insolitus A. aliniger A. christophei A. distichus A. cybotes A. etheridgei

149 As a result of competition, a species’ fundamental niche may differ from its realized niche

150 EXPERIMENT High tide Chthamalus Chthamalus Balanus realized niche
Fig. 54-3 EXPERIMENT High tide Chthamalus Chthamalus realized niche Balanus Balanus realized niche Ocean Low tide RESULTS High tide Figure 54.3 Can a species’ niche be influenced by interspecific competition? Chthamalus fundamental niche Ocean Low tide

151 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

152 Video: Seahorse Camouflage
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

153 (a) Cryptic coloration Canyon tree frog Fig. 54-5a
Figure 54.5a Examples of defensive coloration in animals

154 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

155 (b) Aposematic coloration Poison dart frog Fig. 54-5b
Figure 54.5b Examples of defensive coloration in animals

156 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

157 (c) Batesian mimicry: A harmless species mimics a harmful one.
Fig. 54-5c (c) Batesian mimicry: A harmless species mimics a harmful one. Hawkmoth larva Green parrot snake Figure 54.5c Examples of defensive coloration in animals

158 In Müllerian mimicry, two or more unpalatable species resemble each other

159 Müllerian mimicry: Two unpalatable species mimic each other.
Fig. 54-5d (d) Müllerian mimicry: Two unpalatable species mimic each other. Cuckoo bee Yellow jacket Figure 54.5d Examples of defensive coloration in animals

160 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

161 Symbiosis Symbiosis is a relationship where two or more species live in direct and intimate contact with one another

162 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

163 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

164 Video: Clownfish and Anemone
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

165 (a) Acacia tree and ants (genus Pseudomyrmex)
Fig. 54-7 (a) Acacia tree and ants (genus Pseudomyrmex) Figure 54.7 Mutualism between acacia trees and ants (b) Area cleared by ants at the base of an acacia tree

166 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

167 Fig. 54-8 Figure 54.8 A possible example of commensalism between cattle egrets and water buffalo

168 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

169 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

170 A B C D Community 1 Community 2 A: 25% B: 25% C: 25% D: 25%
Fig. 54-9 A B C D Community 1 Community 2 Figure 54.9 Which forest is more diverse? A: 25% B: 25% C: 25% D: 25% A: 80% B: 5% C: 5% D: 10%

171 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

172 A terrestrial food chain A marine food chain
Fig Quaternary consumers Carnivore Carnivore Tertiary consumers Carnivore Carnivore Secondary consumers Carnivore Carnivore Figure Examples of terrestrial and marine food chains Primary consumers Herbivore Zooplankton Primary producers Plant Phytoplankton A terrestrial food chain A marine food chain

173 Food Webs A food web is a branching food chain with complex trophic interactions

174 Fig Humans Smaller toothed whales Baleen whales Sperm whales Crab-eater seals Leopard seals Elephant seals Birds Fishes Squids Figure An antarctic marine food web Carnivorous plankton Euphausids (krill) Copepods Phyto- plankton

175 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

176 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

177 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.

178 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

179 Field studies of sea stars exhibit their role as a keystone species in intertidal communities

Figure Is Pisaster ochraceus a keystone predator? 20 15 With Pisaster (control) Number of species present 10 5 Without Pisaster (experimental) 1963 ’64 ’65 ’66 ’67 ’68 ’69 ’70 ’71 ’72 ’73 Year

181 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

182 Other ecologists, including A. G. Tansley and H. A
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

183 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

184 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 slow-growing species Low levels of disturbance allow dominant species to exclude less competitive species

185 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

186 Ecological Succession

187 Chapter 55 Ecosystems

188 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

189 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

190 Concept 55.1: Physical laws govern energy flow and chemical cycling in ecosystems
Ecologists study the transformations of energy and matter within their system

191 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

192 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

193 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

194 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)

195 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

196 Microorganisms and other detritivores Secondary consumers
Fig. 55-4 Tertiary consumers Microorganisms and other detritivores Secondary consumers Primary consumers Detritus Primary producers Figure 55.4 An overview of energy and nutrient dynamics in an ecosystem Heat Key Chemical cycling Sun Energy flow

197 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

198 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

199 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

200 TECHNIQUE 80 Snow Clouds 60 Vegetation Percent reflectance 40 Soil 20
Fig. 55-5 TECHNIQUE 80 Snow Clouds 60 Vegetation Percent reflectance 40 Soil 20 Figure 55.5 Determining primary production with satellites Liquid water 400 600 800 1,000 1,200 Visible Near-infrared Wavelength (nm)

201 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

202 1 2 3 Net primary production (kg carbon/m2·yr) · Fig. 55-6
Figure 55.6 Global net primary production in 2002 Net primary production (kg carbon/m2·yr) 1 2 3

203 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

204 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

205 Phytoplankton density (millions of cells per mL)
Fig. 55-7 EXPERIMENT Long Island Shinnecock Bay G F E C D Great South Bay B Moriches Bay A Atlantic Ocean RESULTS 30 Ammonium enriched 24 Phosphate enriched Unenriched control Phytoplankton density (millions of cells per mL) 18 Figure 55.7 Which nutrient limits phytoplankton production along the coast of Long Island? 12 6 A B C D E F G Collection site

206 Upwelling of nutrient-rich waters in parts of the oceans contributes to regions of high primary production

207 Video: Cyanobacteria (Oscillatoria)
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)

208 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

209 Net primary production (g/m2·yr)
Fig. 55-8 3,000 Tropical forest 2,000 Net primary production (g/m2·yr) Temperate forest 1,000 Mountain coniferous forest Figure 55.8 Relationship between net primary production and actual evapotranspiration in six terrestrial ecosystems Desert shrubland Temperate grassland Arctic tundra 500 1,000 1,500 Actual evapotranspiration (mm H2O/yr)

210 On a more local scale, a soil nutrient is often the limiting factor in primary production

211 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

212 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

213 Plant material eaten by caterpillar 200 J 67 J Cellular respiration
Fig. 55-9 Plant material eaten by caterpillar 200 J Figure 55.9 Energy partitioning within a link of the food chain 67 J Cellular respiration 100 J Feces 33 J Growth (new biomass)

214 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

215 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

216 Tertiary consumers 10 J Secondary consumers 100 J Primary 1,000 J
Fig Tertiary consumers 10 J Secondary consumers 100 J Primary consumers 1,000 J Figure An idealized pyramid of net production Primary producers 10,000 J 1,000,000 J of sunlight

217 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

218 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

219 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

220 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

221 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

222 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

223 Transport over land Solar energy Net movement of water vapor by wind
Fig a Transport over land Solar energy Net movement of water vapor by wind Precipitation over land Precipitation over ocean Evaporation from ocean Evapotranspiration from land Figure Nutrient cycles Percolation through soil Runoff and groundwater

224 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

225 Photo- synthesis Cellular respiration Burning of fossil fuels and wood
Fig b CO2 in atmosphere Photosynthesis Photo- synthesis Cellular respiration Burning of fossil fuels and wood Phyto- plankton Higher-level consumers Primary consumers Figure Nutrient cycles Carbon compounds in water Detritus Decomposition

226 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

227 Organic nitrogen is decomposed to NH4+ by ammonification, and NH4+ is decomposed to NO3– by nitrification Denitrification converts NO3– back to N2

228 NO3 – NH3 NH4 + NO2 – N2 in atmosphere Assimilation Denitrifying
Fig c N2 in atmosphere Assimilation Denitrifying bacteria NO3 Nitrogen-fixing bacteria Decomposers Nitrifying bacteria Figure Nutrient cycles Ammonification Nitrification NH3 NH4 + NO2 Nitrogen-fixing soil bacteria Nitrifying bacteria

229 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

230 Precipitation Geologic Weathering uplift of rocks Runoff Consumption
Fig d Precipitation Geologic uplift Weathering of rocks Runoff Consumption Decomposition Plant uptake of PO43– Plankton Dissolved PO43– Soil Uptake Leaching Figure Nutrient cycles Sedimentation

231 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

232 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

233 The research team constructed a dam on the site to monitor loss of water and minerals

234 Nitrate concentration in runoff
Fig (a) Concrete dam and weir (b) Clear-cut watershed 80 Deforested 60 40 Figure Nutrient cycling in the Hubbard Brook Experimental Forest: an example of long-term ecological research 20 Nitrate concentration in runoff (mg/L) 4 Completion of tree cutting 3 Control 2 1 1965 1966 1967 1968 (c) Nitrogen in runoff from watersheds

235 (a) Concrete dam and weir
Fig a Figure 55.16a Nutrient cycling in the Hubbard Brook Experimental Forest: an example of long-term ecological research (a) Concrete dam and weir

236 In one experiment, the trees in one valley were cut down, and the valley was sprayed with herbicides

237 (b) Clear-cut watershed
Fig b Figure 55.16b Nutrient cycling in the Hubbard Brook Experimental Forest: an example of long-term ecological research (b) Clear-cut watershed

238 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

239 Nitrate concentration in runoff
Fig c 80 Deforested 60 40 20 Nitrate concentration in runoff (mg/L) 4 Completion of tree cutting 3 Control 2 1 Figure 55.16c Nutrient cycling in the Hubbard Brook Experimental Forest: an example of long-term ecological research 1965 1966 1967 1968 (c) Nitrogen in runoff from watersheds

240 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

241 Nutrient Enrichment In addition to transporting nutrients from one location to another, humans have added new materials, some of them toxins, to ecosystems

242 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

243 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

244 The dead zone arising from nitrogen pollution in the Mississippi basin
Fig The dead zone arising from nitrogen pollution in the Mississippi basin Figure The dead zone arising from nitrogen pollution in the Mississippi basin Winter Summer

245 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

246 Environmental regulations and new technologies have allowed many developed countries to reduce sulfur dioxide emissions

247 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

248 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

249 Greenhouse Gases and Global Warming
One pressing problem caused by human activities is the rising level of atmospheric carbon dioxide

250 Rising Atmospheric CO2 Levels
Due to the burning of fossil fuels and other human activities, the concentration of atmospheric CO2 has been steadily increasing

251 CO2 concentration (ppm) Average global temperature (ºC)
Fig 14.9 390 14.8 380 14.7 14.6 370 Temperature 14.5 360 14.4 350 14.3 CO2 concentration (ppm) Average global temperature (ºC) 14.2 340 14.1 CO2 330 14.0 Figure Increase in atmospheric carbon dioxide concentration at Mauna Loa, Hawaii, and average global temperatures 13.9 320 13.8 310 13.7 300 13.6 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 Year

252 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

253 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

254 Global warming can be slowed by reducing energy needs and converting to renewable sources of energy
Stabilizing CO2 emissions will require an international effort

255 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

256 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.

257 Conservation Biology and Restoration Ecology
Chapter 56 Conservation Biology and Restoration Ecology

258 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

259 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

260 Three Levels of Biodiversity
Biodiversity has three main components: Genetic diversity Species diversity Ecosystem diversity

261 Genetic Diversity Genetic diversity comprises genetic variation within a population and between populations

262 According to the U.S. Endangered Species Act:
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

263 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

264 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

265 Biodiversity and Human Welfare
Human biophilia allows us to recognize the value of biodiversity for its own sake Species diversity brings humans practical benefits

266 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

267 Fig. 56-6 Figure 56.6 The rosy periwinkle (Catharanthus roseus), a plant that saves lives

268 The loss of species also means loss of genes and genetic diversity
The enormous genetic diversity of organisms has potential for great human benefit

269 Some examples of 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

270 Three Threats to Biodiversity
Most species loss can be traced to three major threats: Habitat destruction Introduced species Overexploitation

271 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

272 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

273 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.

274 Fig. 56-8a Figure 56.8 Two introduced species (a) Brown tree snake

275 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

276 Fig. 56-8b Figure 56.8 Two introduced species (b) Kudzu

277 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

278 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

279 Landscape Structure and Biodiversity
The structure of a landscape can strongly influence biodiversity

280 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

281 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

282 Fig Figure An artificial corridor

283 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

284 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

285 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

286 (a) In 1991, before restoration
Fig Figure A gravel and clay mine site in New Jersey before and after restoration (a) In 1991, before restoration (b) In 2000, near the completion of restoration

287 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

288 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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