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Chapter 51 Animal Behavior PowerPoint® Lecture Presentations for Biology Eighth Edition Neil Campbell and Jane Reece Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • Behavioral ecology is the study of the ecological and evolutionary basis for animal behavior • It integrates proximate and ultimate explanations for animal behavior Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 51-3 (a) (b) Oriented Movement • Environmental cues can trigger movement in a particular direction Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 51-4 Dry open area Sow bug Moist site under leaf • A taxis is a more or less automatic, oriented movement toward or away from a stimulus • Many stream fish exhibit a positive taxis and automatically swim in an upstream direction • This taxis prevents them from being swept away and keeps them facing the direction from which food will come Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Migration • Migration is a regular, long-distance change in location • Animals can orient themselves using – The position of the sun and their circadian clock, an internal 24-hour clock that is an integral part of their nervous system – The position of the North Star – The Earth’s magnetic field Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 51-8 (a) Worker bees (b) Round dance (food near) (c) Waggle dance (food distant) A 30° C B Location A Beehive Location B Location C Pheromones • Many animals that communicate through odors emit chemical substances called pheromones • Pheromones are effective at very low concentrations • When a minnow or catfish is injured, an alarm substance in the fish’s skin disperses in the water, inducing a fright response among fish in the area • Many insects also use pheromones Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 51-9 (a) Minnows before alarm (b) Minnows after alarm Concept 51.2: Learning establishes specific links between experience and behavior • Innate behavior is developmentally fixed and under strong genetic influence. It is inherited. • Learning is the modification of behavior based on specific experiences Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 51-10 (a) Konrad Lorenz and geese (b) Pilot and cranes Spatial Learning • Spatial learning is a more complex modification of behavior based on experience with the spatial structure of the environment • Niko Tinbergen showed how digger wasps use landmarks to find nest entrances Video: Bee Pollinating Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 51-11 EXPERIMENT Nest Pinecone RESULTS Nest No nest Associative Learning • In associative learning, animals associate one feature of their environment with another – For example, a white-footed mouse will avoid eating caterpillars with specific colors after a bad experience with a distasteful monarch butterfly caterpillar Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 51-12 Concept 51.4: Selection for individual survival and reproductive success can explain most behaviors • Genetic components of behavior evolve through natural selection • Behavior can affect fitness by influencing foraging and mate choice Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Evolution of Foraging Behavior • In Drosophila melanogaster, variation in a gene dictates foraging behavior in the larvae • Larvae with one allele travel farther while foraging than larvae with the other allele • Larvae in high-density populations benefit from foraging farther for food, while larvae in lowdensity populations benefit from short-distance foraging Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • Natural selection favors different foraging behavior depending on the density of the population Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • Researchers determined experimentally that the total flight height (which reflects total energy expenditure) was minimized at a drop height of 5m • The average flight height for crows is 5.2 m Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • 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) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Chapter 52 An Introduction to Ecology and the Biosphere PowerPoint® Lecture Presentations for Biology Eighth Edition Neil Campbell and Jane Reece Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Overview: 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • Ecologists consider multiple factors when attempting to explain the distribution of species Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 52-6 Why is species X absent from an area? Yes Does dispersal limit its distribution? No Area inaccessible or insufficient time Does behavior limit its distribution? Yes Habitat selection Yes No Do biotic factors (other species) limit its distribution? No Predation, parasitism, Chemical competition, disease factors Do abiotic factors limit its distribution? Water Oxygen Salinity pH Soil nutrients, etc. Temperature Physical Light factors Soil structure Fire Moisture, etc. Dispersal and Distribution • Dispersal is movement of individuals away from centers of high population density or from their area of origin • Dispersal contributes to global distribution of organisms Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Biotic Factors • Biotic factors that affect the distribution of organisms may include: – Interactions with other species – Predation – Competition Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Abiotic Factors • Abiotic factors affecting distribution of organisms include: – Temperature – Water – Sunlight – Wind – Rocks and soil • Most abiotic factors vary in space and time Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Water • Water availability in habitats is another important factor in species distribution • Desert organisms exhibit adaptations for water conservation Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Salinity • Salt concentration affects water balance of organisms through osmosis • Few terrestrial organisms are adapted to highsalinity habitats Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Rocks and Soil • Many characteristics of soil limit distribution of plants and thus the animals that feed upon them: – Physical structure – pH – Mineral composition Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Aquatic Biomes • Major aquatic biomes can be characterized by their physical environment, chemical environment, geological features, photosynthetic organisms, and heterotrophs Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 52-19 Tropical forest Savanna Desert 30ºN Tropic of Cancer Equator Tropic of Capricorn 30ºS Chaparral Temperate grassland Temperate broadleaf forest Northern coniferous forest Tundra High mountains Polar ice Climate and Terrestrial Biomes • Climate has a great impact on the distribution of organisms • This can be illustrated with a climograph, a plot of the temperature and precipitation in a region • Biomes are affected not just by average temperature and precipitation, but also by the pattern of temperature and precipitation through the year Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Terrestrial Biomes • Terrestrial biomes can be characterized by distribution, precipitation, temperature, plants, and animals Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Chapter 53 Population Ecology PowerPoint® Lecture Presentations for Biology Eighth Edition Neil Campbell and Jane Reece Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Patterns of Dispersion • Environmental and social factors influence spacing of individuals in a population Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 53-4 (a) Clumped (b) Uniform (c) Random Demographics • Demography is the study of the vital statistics of a population and how they change over time • Death rates and birth rates are of particular interest to demographers • A life table is an age-specific summary of the survival pattern of a population • It is best made by following the fate of a cohort, a group of individuals of the same age • A survivorship curve is a graphic way of representing the data in a life table Number of survivors (log scale) Fig. 53-6 1,000 I 100 II 10 III 1 0 50 Percentage of maximum life span 100 Concept 53.2: Life history traits are products of natural selection • An organism’s life history comprises the traits that affect its schedule of reproduction and survival: – The age at which reproduction begins – How often the organism reproduces – How many offspring are produced during each reproductive cycle • Life history traits are evolutionary outcomes reflected in the development, physiology, and behavior of an organism Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 53-7 “Trade-offs” and Life Histories • Organisms have finite resources, which may lead to trade-offs between survival and reproduction Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • Some plants produce a large number of small seeds, ensuring that at least some of them will grow and eventually reproduce Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 53-9a (a) Dandelion • Other types of plants produce a moderate number of large seeds that provide a large store of energy that will help seedlings become established Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 53-9b (b) Coconut palm • In animals, parental care of smaller broods may facilitate survival of offspring Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 53-8 Parents surviving the following winter (%) RESULTS 100 Male Female 80 60 40 20 0 Reduced brood size Normal brood size Enlarged brood size Concept 53.3: The exponential model describes population growth in an idealized, unlimited environment • It is useful to study population growth in an idealized situation • Idealized situations help us understand the capacity of species to increase and the conditions that may facilitate this growth Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • Equation of exponential population growth: dN rmaxN dt Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • Exponential population growth results in a Jshaped curve Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 53-10 2,000 Population size (N) dN = 1.0N dt 1,500 dN = 0.5N dt 1,000 500 0 0 5 10 Number of generations 15 • The J-shaped curve of exponential growth characterizes some rebounding populations Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 53-11 Elephant population 8,000 6,000 4,000 2,000 0 1900 1920 1940 Year 1960 1980 Concept 53.4: The logistic model describes how a population grows more slowly as it nears its carrying capacity • Exponential growth cannot be sustained for long in any population • A more realistic population model limits growth by incorporating carrying capacity • Carrying capacity (K) is the maximum population size the environment can support Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The Logistic Growth Model • In the logistic population growth model, the per capita rate of increase declines as carrying capacity is reached • We construct the logistic model by starting with the exponential model and adding an expression that reduces per capita rate of increase as N approaches K (K N) dN rmax N dt K Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Table 53-3 • The logistic model of population growth produces a sigmoid (S-shaped) curve Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 53-12 Exponential growth Population size (N) 2,000 dN = 1.0N dt 1,500 K = 1,500 Logistic growth 1,000 dN = 1.0N dt 1,500 – N 1,500 500 0 0 5 10 Number of generations 15 The Logistic Model and Real Populations • The growth of laboratory populations of paramecia fits an S-shaped curve • These organisms are grown in a constant environment lacking predators and competitors Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Number of Daphnia/50 mL Number of Paramecium/mL Fig. 53-13 1,000 800 600 400 200 0 180 150 120 90 60 30 0 0 5 10 Time (days) 15 (a) A Paramecium population in the lab 0 20 40 60 80 100 120 Time (days) (b) A Daphnia population in the lab 140 160 Number of Paramecium/mL Fig. 53-13a 1,000 800 600 400 200 0 0 5 10 Time (days) 15 (a) A Paramecium population in the lab • Some populations overshoot K before settling down to a relatively stable density Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Number of Daphnia/50 mL Fig. 53-13b 180 150 120 90 60 30 0 0 20 40 60 80 100 120 Time (days) (b) A Daphnia population in the lab 140 160 The Logistic Model and Life Histories • Life history traits favored by natural selection may vary with population density and environmental conditions • K-selection, or density-dependent selection, selects for life history traits that are sensitive to population density • r-selection, or density-independent selection, selects for life history traits that maximize reproduction Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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? Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Competition for Resources • In crowded populations, increasing population density intensifies competition for resources and results in a lower birth rate Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Percentage of juveniles producing lambs Fig. 53-16 100 80 60 40 20 0 200 300 400 500 Population size 600 Territoriality • In many vertebrates and some invertebrates, competition for territory may limit density • Cheetahs are highly territorial, using chemical communication to warn other cheetahs of their boundaries Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Disease • Population density can influence the health and survival of organisms • In dense populations, pathogens can spread more rapidly Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Predation • As a prey population builds up, predators may feed preferentially on that species Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Intrinsic Factors • For some populations, intrinsic (physiological) factors appear to regulate population size Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Population Dynamics • The study of population dynamics focuses on the complex interactions between biotic and abiotic factors that cause variation in population size Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Stability and Fluctuation • Long-term population studies have challenged the hypothesis that populations of large mammals are relatively stable over time • Weather can affect population size over time Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 53-18 2,100 Number of sheep 1,900 1,700 1,500 1,300 1,100 900 700 500 0 1955 1965 1975 1985 Year 1995 2005 • Changes in predation pressure can drive population fluctuations Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 53-19 2,500 50 Moose 40 2,000 30 1,500 20 1,000 10 500 0 1955 1965 1975 1985 Year 1995 0 2005 Number of moose Number of wolves Wolves Population Cycles: Scientific Inquiry • Some populations undergo regular boom-andbust cycles • Lynx populations follow the 10 year boom-andbust cycle of hare populations • Three hypotheses have been proposed to explain the hare’s 10-year interval Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 53-20 Snowshoe hare 120 9 Lynx 80 6 40 3 0 0 1850 1875 1900 Year 1925 Number of lynx (thousands) Number of hares (thousands) 160 • Hypothesis: The hare’s population cycle follows a cycle of winter food supply • If this hypothesis is correct, then the cycles should stop if the food supply is increased • Additional food was provided experimentally to a hare population, and the whole population increased in size but continued to cycle • No hares appeared to have died of starvation Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • Hypothesis: The hare’s population cycle is driven by pressure from other predators • In a study conducted by field ecologists, 90% of the hares were killed by predators • These data support this second hypothesis Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • Hypothesis: The hare’s population cycle is linked to sunspot cycles • Sunspot activity affects light quality, which in turn affects the quality of the hares’ food • There is good correlation between sunspot activity and hare population size Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • The results of all these experiments suggest that both predation and sunspot activity regulate hare numbers and that food availability plays a less important role Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The Global Human Population • The human population increased relatively slowly until about 1650 and then began to grow exponentially Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 53-22 6 5 4 3 2 The Plague 1 0 8000 B.C.E. 4000 3000 2000 1000 B.C.E. B.C.E. B.C.E. B.C.E. 0 1000 C.E. 2000 C.E. Human population (billions) 7 • Though the global population is still growing, the rate of growth began to slow during the 1960s Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Age Structure • One important demographic factor in present and future growth trends is a country’s age structure • Age structure is the relative number of individuals at each age Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 53-25 Rapid growth Afghanistan Male Female 10 8 6 4 2 0 2 4 6 Percent of population Age 85+ 80–84 75–79 70–74 65–69 60–64 55–59 50–54 45–49 40–44 35–39 30–34 25–29 20–24 15–19 10–14 5–9 0–4 8 10 8 Slow growth United States Male Female 6 4 2 0 2 4 6 Percent of population Age 85+ 80–84 75–79 70–74 65–69 60–64 55–59 50–54 45–49 40–44 35–39 30–34 25–29 20–24 15–19 10–14 5–9 0–4 8 8 No growth Italy Male Female 6 4 2 0 2 4 6 8 Percent of population • Age structure diagrams can predict a population’s growth trends • They can illuminate social conditions and help us plan for the future Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Global Carrying Capacity • How many humans can the biosphere support? Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Estimates of Carrying Capacity • The carrying capacity of Earth for humans is uncertain • The average estimate is 10–15 billion Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Limits on Human Population Size • The ecological footprint concept summarizes the aggregate land and water area needed to sustain the people of a nation • It is one measure of how close we are to the carrying capacity of Earth • Countries vary greatly in footprint size and available ecological capacity Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 53-27 Log (g carbon/year) 13.4 9.8 5.8 Not analyzed • Our carrying capacity could potentially be limited by food, space, nonrenewable resources, or buildup of wastes Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Chapter 54 Community Ecology PowerPoint® Lecture Presentations for Biology Eighth Edition Neil Campbell and Jane Reece Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Overview: A Sense of Community • A biological community is an assemblage of populations of various species living close enough for potential interaction Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Competition • Interspecific competition (–/– interaction) occurs when species compete for a resource in short supply Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • Resource partitioning is differentiation of ecological niches, enabling similar species to coexist in a community Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 54-2 A. distichus perches on fence posts and other sunny surfaces. A. insolitus usually perches on shady branches. A. ricordii A. insolitus A. aliniger A. distichus A. christophei A. cybotes A. etheridgei • As a result of competition, a species’ fundamental niche may differ from its realized niche Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 54-3 EXPERIMENT Chthamalus Balanus High tide Chthamalus realized niche Balanus realized niche Ocean Low tide RESULTS High tide Chthamalus fundamental niche Ocean Low tide Predation • Predation (+/– interaction) refers to interaction where one species, the predator, kills and eats the other, the prey • Some feeding adaptations of predators are claws, teeth, fangs, stingers, and poison Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 54-5a (a) Cryptic coloration Canyon tree frog • Animals with effective chemical defense often exhibit bright warning coloration, called aposematic coloration • Predators are particularly cautious in dealing with prey that display such coloration Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 54-5b (b) Aposematic coloration Poison dart frog • In some cases, a prey species may gain significant protection by mimicking the appearance of another species • In Batesian mimicry, a palatable or harmless species mimics an unpalatable or harmful model Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 54-5c (c) Batesian mimicry: A harmless species mimics a harmful one. Hawkmoth larva Green parrot snake • In Müllerian mimicry, two or more unpalatable species resemble each other Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 54-5d (d) Müllerian mimicry: Two unpalatable species mimic each other. Cuckoo bee Yellow jacket Herbivory • Herbivory (+/– interaction) refers to an interaction in which an herbivore eats parts of a plant or alga • It has led to evolution of plant mechanical and chemical defenses and adaptations by herbivores Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Symbiosis • Symbiosis is a relationship where two or more species live in direct and intimate contact with one another Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 54-7 (a) Acacia tree and ants (genus Pseudomyrmex) (b) Area cleared by ants at the base of an acacia tree Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 54-8 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Concept 54.2: Dominant and keystone species exert strong controls on community structure • In general, a few species in a community exert strong control on that community’s structure • Two fundamental features of community structure are species diversity and feeding relationships Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Species Diversity • Species diversity of a community is the variety of organisms that make up the community • It has two components: species richness and relative abundance • Species richness is the total number of different species in the community • Relative abundance is the proportion each species represents of the total individuals in the community Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 54-9 A B C D Community 1 A: 25% B: 25% C: 25% D: 25% Community 2 A: 80% B: 5% C: 5% D: 10% Trophic Structure • Trophic structure is the feeding relationships between organisms in a community • It is a key factor in community dynamics • Food chains link trophic levels from producers to top carnivores Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 54-11 Quaternary consumers Carnivore Carnivore Tertiary consumers Carnivore Carnivore Secondary consumers Carnivore Carnivore Primary consumers Herbivore Zooplankton Primary producers Plant Phytoplankton A terrestrial food chain A marine food chain Food Webs • A food web is a branching food chain with complex trophic interactions Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 54-12 Humans Smaller toothed whales Baleen whales Crab-eater seals Birds Leopard seals Fishes Sperm whales Elephant seals Squids Carnivorous plankton Euphausids (krill) Copepods Phytoplankton Species with a Large Impact • Certain species have a very large impact on community structure • Such species are highly abundant or play a pivotal role in community dynamics Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • 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. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • Field studies of sea stars exhibit their role as a keystone species in intertidal communities Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 54-15 EXPERIMENT Number of species present RESULTS 20 15 With Pisaster (control) 10 5 Without Pisaster (experimental) 0 1963 ’64 ’65 ’66 ’67 ’68 ’69 ’70 ’71 ’72 ’73 Year Concept 54.3: Disturbance influences species diversity and composition • Decades ago, most ecologists favored the view that communities are in a state of equilibrium • This view was supported by F. E. Clements who suggested that species in a climax community function as a superorganism Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • Other ecologists, including A. G. Tansley and H. A. Gleason, challenged whether communities were at equilibrium • Recent evidence of change has led to a nonequilibrium model, which describes communities as constantly changing after being buffeted by disturbances Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Characterizing Disturbance • A disturbance is an event that changes a community, removes organisms from it, and alters resource availability • Fire is a significant disturbance in most terrestrial ecosystems • It is often a necessity in some communities Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • The intermediate disturbance hypothesis suggests that moderate levels of disturbance can foster greater diversity than either high or low levels of disturbance • High levels of disturbance exclude many slowgrowing species • Low levels of disturbance allow dominant species to exclude less competitive species Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Ecological Succession Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Chapter 55 Ecosystems PowerPoint® Lecture Presentations for Biology Eighth Edition Neil Campbell and Jane Reece Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Overview: Observing Ecosystems • An ecosystem consists of all the organisms living in a community, as well as the abiotic factors with which they interact • Ecosystems range from a microcosm, such as an aquarium, to a large area such as a lake or forest Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • Regardless of an ecosystem’s size, its dynamics involve two main processes: energy flow and chemical cycling • Energy flows through ecosystems while matter cycles within them Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Concept 55.1: Physical laws govern energy flow and chemical cycling in ecosystems • Ecologists study the transformations of energy and matter within their system Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Conservation of Mass • The law of conservation of mass states that matter cannot be created or destroyed • Chemical elements are continually recycled within ecosystems • In a forest ecosystem, most nutrients enter as dust or solutes in rain and are carried away in water • Ecosystems are open systems, absorbing energy and mass and releasing heat and waste products Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Energy, Mass, and Trophic Levels • Autotrophs build molecules themselves using photosynthesis or chemosynthesis as an energy source; heterotrophs depend on the biosynthetic output of other organisms • Energy and nutrients pass from primary producers (autotrophs) to primary consumers (herbivores) to secondary consumers (carnivores) to tertiary consumers (carnivores that feed on other carnivores) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • Detritivores, or decomposers, are consumers that derive their energy from detritus, nonliving organic matter • Prokaryotes and fungi are important detritivores • Decomposition connects all trophic levels Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 55-4 Tertiary consumers Microorganisms and other detritivores Detritus Secondary consumers Primary consumers Primary producers Heat Key Chemical cycling Energy flow Sun Ecosystem Energy Budgets • The amount of light energy converted to chemical energy by autotrophs is an ecosystem’s primary production • The extent of photosynthetic production sets the spending limit for an ecosystem’s energy budget Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The Global Energy Budget • The amount of solar radiation reaching the Earth’s surface limits photosynthetic output of ecosystems • Only a small fraction of solar energy actually strikes photosynthetic organisms, and even less is of a usable wavelength Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Gross and Net Primary Production • Total primary production is known as the ecosystem’s gross primary production (GPP) • Net primary production (NPP) is GPP minus energy used by primary producers for respiration • Only NPP is available to consumers • Ecosystems vary greatly in NPP and contribution to the total NPP on Earth • Standing crop is the total biomass of photosynthetic autotrophs at a given time Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 55-5 TECHNIQUE 80 Snow Clouds 60 Vegetation 40 Soil 20 Liquid water 0 400 600 Visible 800 1,000 Near-infrared Wavelength (nm) 1,200 • Tropical rain forests, estuaries, and coral reefs are among the most productive ecosystems per unit area • Marine ecosystems are relatively unproductive per unit area, but contribute much to global net primary production because of their volume Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 55-6 Net primary production (kg carbon/m2·yr) · 0 1 2 3 Primary Production in Aquatic Ecosystems • In marine and freshwater ecosystems, both light and nutrients control primary production • Depth of light penetration affects primary production in the photic zone of an ocean or lake Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Nutrient Limitation • More than light, nutrients limit primary production in geographic regions of the ocean and in lakes • A limiting nutrient is the element that must be added for production to increase in an area • Nitrogen and phosphorous are typically the nutrients that most often limit marine production • Nutrient enrichment experiments confirmed that nitrogen was limiting phytoplankton growth off the shore of Long Island, New York Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 55-7 EXPERIMENT B C D E F G Shinnecock Bay Moriches Bay Atlantic Ocean A Phytoplankton density (millions of cells per mL) RESULTS 30 Ammonium enriched 24 Phosphate enriched 18 Unenriched control 12 6 0 A B C D E Collection site F G • Upwelling of nutrient-rich waters in parts of the oceans contributes to regions of high primary production Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • The addition of large amounts of nutrients to lakes has a wide range of ecological impacts • In some areas, sewage runoff has caused eutrophication of lakes, which can lead to loss of most fish species Video: Cyanobacteria (Oscillatoria) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Primary Production in Terrestrial Ecosystems • In terrestrial ecosystems, temperature and moisture affect primary production on a large scale • Actual evapotranspiration can represent the contrast between wet and dry climates • Actual evapotranspiration is the water annually transpired by plants and evaporated from a landscape • It is related to net primary production Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 55-8 Net primary production (g/m2··yr) 3,000 Tropical forest 2,000 Temperate forest 1,000 Mountain coniferous forest Desert shrubland Temperate grassland Arctic tundra 0 0 500 1,500 1,000 Actual evapotranspiration (mm H2O/yr) • On a more local scale, a soil nutrient is often the limiting factor in primary production Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Production Efficiency • When a caterpillar feeds on a leaf, only about one-sixth of the leaf’s energy is used for secondary production • An organism’s production efficiency is the fraction of energy stored in food that is not used for respiration Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 55-9 Plant material eaten by caterpillar 200 J 67 J Feces 100 J 33 J Growth (new biomass) Cellular respiration Trophic Efficiency and Ecological Pyramids • Trophic efficiency is the percentage of production transferred from one trophic level to the next • It usually ranges from 5% to 20% • Trophic efficiency is multiplied over the length of a food chain Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • Approximately 0.1% of chemical energy fixed by photosynthesis reaches a tertiary consumer • A pyramid of net production represents the loss of energy with each transfer in a food chain Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 55-10 Tertiary consumers Secondary consumers 10 J 100 J Primary consumers 1,000 J Primary producers 10,000 J 1,000,000 J of sunlight • In a biomass pyramid, each tier represents the dry weight of all organisms in one trophic level • Most biomass pyramids show a sharp decrease at successively higher trophic levels Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • Dynamics of energy flow in ecosystems have important implications for the human population • Eating meat is a relatively inefficient way of tapping photosynthetic production • Worldwide agriculture could feed many more people if humans ate only plant material Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Concept 55.4: Biological and geochemical processes cycle nutrients between organic and inorganic parts of an ecosystem • Life depends on recycling chemical elements • Nutrient circuits in ecosystems involve biotic and abiotic components and are often called biogeochemical cycles Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Biogeochemical Cycles • Gaseous carbon, oxygen, sulfur, and nitrogen occur in the atmosphere and cycle globally • Less mobile elements such as phosphorus, potassium, and calcium cycle on a more local level • A model of nutrient cycling includes main reservoirs of elements and processes that transfer elements between reservoirs • All elements cycle between organic and inorganic reservoirs Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • In studying cycling of water, carbon, nitrogen, and phosphorus, ecologists focus on four factors: – Each chemical’s biological importance – Forms in which each chemical is available or used by organisms – Major reservoirs for each chemical – Key processes driving movement of each chemical through its cycle Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The Water Cycle • Water is essential to all organisms • 97% of the biosphere’s water is contained in the oceans, 2% is in glaciers and polar ice caps, and 1% is in lakes, rivers, and groundwater • Water moves by the processes of evaporation, transpiration, condensation, precipitation, and movement through surface and groundwater Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 55-14a Transport over land Solar energy Net movement of water vapor by wind Precipitation Evaporation over ocean from ocean Precipitation over land Evapotranspiration from land Percolation through soil Runoff and groundwater The Carbon Cycle • Carbon-based organic molecules are essential to all organisms • Carbon reservoirs include fossil fuels, soils and sediments, solutes in oceans, plant and animal biomass, and the atmosphere • CO2 is taken up and released through photosynthesis and respiration; additionally, volcanoes and the burning of fossil fuels contribute CO2 to the atmosphere Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 55-14b CO2 in atmosphere Photosynthesis Photosynthesis Cellular respiration Burning of fossil fuels Phytoand wood plankton Higher-level consumers Primary consumers Carbon compounds in water Detritus Decomposition The Terrestrial Nitrogen Cycle • Nitrogen is a component of amino acids, proteins, and nucleic acids • The main reservoir of nitrogen is the atmosphere (N2), though this nitrogen must be converted to NH4+ or NO3– for uptake by plants, via nitrogen fixation by bacteria Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • Organic nitrogen is decomposed to NH4+ by ammonification, and NH4+ is decomposed to NO3– by nitrification • Denitrification converts NO3– back to N2 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 55-14c N2 in atmosphere Assimilation NO3– Nitrogen-fixing bacteria Decomposers Ammonification NH3 Nitrogen-fixing soil bacteria Nitrification NH4+ NO2– Nitrifying bacteria Denitrifying bacteria Nitrifying bacteria The Phosphorus Cycle • Phosphorus is a major constituent of nucleic acids, phospholipids, and ATP • Phosphate (PO43–) is the most important inorganic form of phosphorus • The largest reservoirs are sedimentary rocks of marine origin, the oceans, and organisms • Phosphate binds with soil particles, and movement is often localized Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 55-14d Precipitation Geologic uplift Weathering of rocks Runoff Consumption Decomposition Plant uptake of PO43– Plankton Dissolved PO43– Uptake Sedimentation Soil Leaching Decomposition and Nutrient Cycling Rates • Decomposers (detritivores) play a key role in the general pattern of chemical cycling • Rates at which nutrients cycle in different ecosystems vary greatly, mostly as a result of differing rates of decomposition • The rate of decomposition is controlled by temperature, moisture, and nutrient availability • Rapid decomposition results in relatively low levels of nutrients in the soil Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • The research team constructed a dam on the site to monitor loss of water and minerals Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 55-16 (a) Concrete dam and weir Nitrate concentration in runoff (mg/L) (b) Clear-cut watershed 80 60 40 20 4 3 2 1 0 Deforested Completion of tree cutting 1965 Control 1966 (c) Nitrogen in runoff from watersheds 1967 1968 Fig. 55-16a (a) Concrete dam and weir • In one experiment, the trees in one valley were cut down, and the valley was sprayed with herbicides Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 55-16b (b) Clear-cut watershed • Net losses of water and minerals were studied and found to be greater than in an undisturbed area • These results showed how human activity can affect ecosystems Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Nitrate concentration in runoff (mg/L) Fig. 55-16c 80 Deforested 60 40 20 4 3 Completion of tree cutting Control 2 1 0 1965 1966 (c) Nitrogen in runoff from watersheds Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 1967 1968 Concept 55.5: Human activities now dominate most chemical cycles on Earth • As the human population has grown, our activities have disrupted the trophic structure, energy flow, and chemical cycling of many ecosystems Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Nutrient Enrichment • In addition to transporting nutrients from one location to another, humans have added new materials, some of them toxins, to ecosystems Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 55-18 The dead zone arising from nitrogen pollution in the Mississippi basin Winter Summer Acid Precipitation • Combustion of fossil fuels is the main cause of acid precipitation • North American and European ecosystems downwind from industrial regions have been damaged by rain and snow containing nitric and sulfuric acid • Acid precipitation changes soil pH and causes leaching of calcium and other nutrients Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • Environmental regulations and new technologies have allowed many developed countries to reduce sulfur dioxide emissions Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Greenhouse Gases and Global Warming • One pressing problem caused by human activities is the rising level of atmospheric carbon dioxide Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Rising Atmospheric CO2 Levels • Due to the burning of fossil fuels and other human activities, the concentration of atmospheric CO2 has been steadily increasing Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 55-21 14.9 390 14.8 380 14.7 14.6 370 Temperature 14.5 360 14.4 14.3 350 14.2 340 14.1 CO2 330 14.0 13.9 320 13.8 310 13.7 13.6 300 1960 1965 1970 1975 1980 1985 Year 1990 1995 2000 2005 The Greenhouse Effect and Climate • CO2, water vapor, and other greenhouse gases reflect infrared radiation back toward Earth; this is the greenhouse effect • This effect is important for keeping Earth’s surface at a habitable temperature • Increased levels of atmospheric CO2 are magnifying the greenhouse effect, which could cause global warming and climatic change Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • Global warming can be slowed by reducing energy needs and converting to renewable sources of energy • Stabilizing CO2 emissions will require an international effort Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • 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. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Chapter 56 Conservation Biology and Restoration Ecology PowerPoint® Lecture Presentations for Biology Eighth Edition Neil Campbell and Jane Reece Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Overview: Striking Gold • 1.8 million species have been named and described • Biologists estimate 10–200 million species exist on Earth • Tropical forests contain some of the greatest concentrations of species and are being destroyed at an alarming rate • Humans are rapidly pushing many species toward extinction Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Three Levels of Biodiversity • Biodiversity has three main components: – Genetic diversity – Species diversity – Ecosystem diversity Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Genetic Diversity • Genetic diversity comprises genetic variation within a population and between populations Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Biodiversity and Human Welfare • Human biophilia allows us to recognize the value of biodiversity for its own sake • Species diversity brings humans practical benefits Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 56-6 • The loss of species also means loss of genes and genetic diversity • The enormous genetic diversity of organisms has potential for great human benefit Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Three Threats to Biodiversity • Most species loss can be traced to three major threats: – Habitat destruction – Introduced species – Overexploitation Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • 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. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 56-8a (a) Brown tree snake • Humans have deliberately introduced some species with good intentions but disastrous effects • An example is the introduction of kudzu in the southern United States • This bushy weed grows so fast it can cover large areas in very little time, crowding out other native plants Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 56-8b (b) Kudzu Overexploitation • Overexploitation is human harvesting of wild plants or animals at rates exceeding the ability of populations of those species to rebound • Overexploitation by the fishing industry has greatly reduced populations of some game fish, such as bluefin tuna and Atlantic cod • Passenger pigeons once numbered in the millions but were hunted to extinction Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Landscape Structure and Biodiversity • The structure of a landscape can strongly influence biodiversity Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 56-16 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 56-21 (a) In 1991, before restoration (b) In 2000, near the completion of restoration Bioremediation • Bioremediation is the use of living organisms to detoxify ecosystems • The organisms most often used are prokaryotes, fungi, or plants • These organisms can take up, and sometimes metabolize, toxic molecules Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings