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16 ch53populationecology2008
- 2. AP Biology Life takes place in populations Population group of individuals of same species in same area at same time rely on same resources interact interbreed rely on same resources interact interbreed Population Ecology: What factors affect a population?Population Ecology: What factors affect a population?
- 3. AP Biology Why Population Ecology? Scientific goal understanding the factors that influence the size of populations general principles specific cases Practical goal management of populations increase population size endangered species decrease population size pests maintain population size fisheries management maintain & maximize sustained yield QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
- 4. AP Biology Abiotic factors sunlight & temperature precipitation / water soil / nutrients Biotic factors other living organisms prey (food) competitors predators, parasites, disease Intrinsic factors adaptations Factors that affect Population Size
- 5. AP Biology Characterizing a Population Describing a population population range pattern of spacing density size of population 1937 1943 1951 1958 1961 1960 19651964 1966 1970 1970 1956 Immigration from Africa ~1900 Equator range density
- 6. AP Biology Population Range Geographical limitations abiotic & biotic factors temperature, rainfall, food, predators, etc. habitat adaptations to polar biome adaptations to polar biome adaptations to rainforest biome adaptations to rainforest biome
- 7. AP Biology Changes in range Range expansions & contractions changing environment Woodlands Grassland, chaparral, and desert scrub 15,000 years ago glacial periodAlpine tundra Spruce-fir forests Mixed conifer forest 0 km 2 km 3 km 1 km Elevation(km) PresentAlpine tundra Spruce-fir forests Mixed conifer forest Woodlands Grassland, chaparral, and desert scrub aspen oak, maple white birch sequoia result of competitionresult of competition
- 8. AP Biology At risk populations Endangered species limitations to range / habitat places species at risk Socorro isopod Devil’s hole pupfish Iriomote cat Northern white rhinoceros New Guinea tree kangaroo Iiwi Hawaiian bird Catalina Island mahogany tree
- 9. AP Biology Population Spacing Dispersal patterns within a population uniform random clumped Provides insight into the environmental associations & social interactions of individuals in population Provides insight into the environmental associations & social interactions of individuals in population
- 10. AP Biology Clumped Pattern (most common)
- 11. AP Biology Uniform Clumped patterns May result from direct interactions between individuals in the population → territoriality
- 12. AP Biology Population Size Changes to population size adding & removing individuals from a population birth death immigration emigration
- 13. AP Biology Population growth rates Factors affecting population growth rate sex ratio how many females vs. males? generation time at what age do females reproduce? age structure how females at reproductive age in cohort?
- 14. AP Biology Life tableLife table Demography Factors that affect growth & decline of populations vital statistics & how they change over time Why do teenage boys pay high car insurance rates?Why do teenage boys pay high car insurance rates? females males What adaptations have led to this difference in male vs. female mortality?
- 15. AP Biology Survivorship curves Graphic representation of life table Belding ground squirrel The relatively straight lines of the plots indicate relatively constant rates of death; however, males have a lower survival rate overall than females. The relatively straight lines of the plots indicate relatively constant rates of death; however, males have a lower survival rate overall than females.
- 16. AP Biology Age structure Relative number of individuals of each age What do these data imply about population growth in these countries?
- 17. AP Biology Survivorship curves Generalized strategies What do these graphs tell about survival & strategy of a species? What do these graphs tell about survival & strategy of a species? 0 25 1000 100 Human (type I) Hydra (type II) Oyster (type III) 10 1 50 Percent of maximum life span 10075 Survivalperthousand I. High death rate in post-reproductive years I. High death rate in post-reproductive years II. Constant mortality rate throughout life span II. Constant mortality rate throughout life span III. Very high early mortality but the few survivors then live long (stay reproductive) III. Very high early mortality but the few survivors then live long (stay reproductive)
- 18. AP Biology Trade-offs: survival vs. reproduction The cost of reproduction increase reproduction may decrease survival age at first reproduction investment per offspring number of reproductive cycles per lifetime Natural selection favors a life history that maximizes lifetime reproductive success Natural selection favors a life history that maximizes lifetime reproductive success
- 19. AP Biology Parental survival Kestrel Falcons: The cost of larger broods to both male & female parents
- 20. AP Biology Reproductive strategies K-selected late reproduction few offspring invest a lot in raising offspring primates coconut r-selected early reproduction many offspring little parental care insects many plants K-selected r-selected
- 21. AP Biology Trade offs Number & size of offspring vs. Survival of offspring or parent Number & size of offspring vs. Survival of offspring or parent r-selected K-selected “Of course, long before you mature, most of you will be eaten.”
- 22. AP Biology Life strategies & survivorship curves 0 25 1000 100 Human (type I) Hydra (type II) Oyster (type III) 10 1 50 Percent of maximum life span 10075 Survivalperthousand K-selection r-selection
- 23. AP Biology Population growth change in population = births – deaths Exponential model (ideal conditions) dN = riN dt N = # of individuals r = rate of growth ri = intrinsic rate t = time d = rate of change growth increasing at constant rate intrinsic rate = maximum rate of growth every pair has 4 offspring every pair has 4 offspring every pair has 3 offspring every pair has 3 offspring
- 24. AP Biology African elephant protected from hunting Whooping crane coming back from near extinction Exponential growth rate Characteristic of populations without limiting factors introduced to a new environment or rebounding from a catastrophe
- 25. AP Biology Regulation of population size Limiting factors density dependent competition: food, mates, nesting sites predators, parasites, pathogens density independent abiotic factors sunlight (energy) temperature rainfall swarming locusts marking territory = competition competition for nesting sites
- 26. AP Biology Introduced species Non-native species transplanted populations grow exponentially in new area out-compete native species loss of natural controls lack of predators, parasites, competitors reduce diversity examples African honeybee gypsy moth zebra mussel purple loosestrife kudzu gypsy moth
- 27. AP Biology Zebra mussel ecological & economic damage ~2 months reduces diversity loss of food & nesting sites for animals economic damage reduces diversity loss of food & nesting sites for animals economic damage
- 28. AP Biology Purple loosestrife 19681968 19781978 reduces diversity loss of food & nesting sites for animals reduces diversity loss of food & nesting sites for animals
- 29. AP Biology K = carrying capacity K = carrying capacity Logistic rate of growth Can populations continue to grow exponentially? Of course not!Of course not! effect of natural controls effect of natural controls no natural controlsno natural controls What happens as N approaches K?
- 30. AP Biology 500 400 300 200 100 0 200 10 30 5040 60 Time (days) Numberofcladocerans (per200ml) Maximum population size that environment can support with no degradation of habitat varies with changes in resources Time (years) 1915 1925 1935 1945 10 8 6 4 2 0 Numberofbreedingmale furseals(thousands) Carrying capacity What’s going on with the plankton?
- 31. AP Biology Changes in Carrying Capacity Population cycles predator – prey interactions At what population level is the carrying capacity? KK KK
- 32. AP Biology Human population growth What factors have contributed to this exponential growth pattern? What factors have contributed to this exponential growth pattern? 1650→500 million 2005→6 billion Industrial Revolution Significant advances in medicine through science and technology Bubonic plague "Black Death" Population of… China: 1.3 billion India: 1.1 billion adding 82 million/year ~ 200,000 per day! adding 82 million/year ~ 200,000 per day! Doubling times 250m → 500m = y () 500m → 1b = y () 1b → 2b = 80y (1850–1930) 2b → 4b = 75y (1930–1975) Doubling times 250m → 500m = y () 500m → 1b = y () 1b → 2b = 80y (1850–1930) 2b → 4b = 75y (1930–1975) Is the human population reaching carrying capacity?
- 33. AP Biology Distribution of population growth 1 2 3 Time 19501900 2000 Developing countries 2050 4 5 6 7 8 9 10 11 0 Developed countries low fertility Worldpopulationinbillions World total medium fertility high fertility uneven distribution of population: 90% of births are in developing countries uneven distribution of population: 90% of births are in developing countries uneven distribution of resources: wealthiest 20% consumes ~90% of resources increasing gap between rich & poor uneven distribution of resources: wealthiest 20% consumes ~90% of resources increasing gap between rich & poor What is K for humans? 10-15 billion? There are choices as to which future path the world takes… There are choices as to which future path the world takes… the effect of income & education the effect of income & education
- 34. AP Biology Ecological Footprint 30.2 15.6 6.4 3.7 3.2 2.6 USA Germany Brazil Indonesia Nigeria India Amount of land required to support an individual at standard of living of population 20 4 6 8 1210 14 16 18 20 22 24 26 28 30 32 34 Acres uneven distribution: wealthiest 20% of world: 86% consumption of resources 53% of CO2 emissions uneven distribution: wealthiest 20% of world: 86% consumption of resources 53% of CO2 emissions over-population orover-population or over-consumption?over-consumption? over-population orover-population or over-consumption?over-consumption?
- 35. AP Biology Ecological Footprint Based on land & water area used to produce all resources each country consumes & to absorb all wastes it generates Based on land & water area used to produce all resources each country consumes & to absorb all wastes it generates deficit surplus
- 37. AP Biology Difficult to count a moving target Measuring population density How do we measure how many individuals in a population? number of individuals in an area mark & recapture methods sampling populations
- 38. AP Biology Evolutionary adaptations Coping with environmental variation regulators endotherms homeostasis (“warm-blooded”) conformers ectotherms (“cold-blooded”)
- 39. AP Biology Bright blue marble spinning in space Ecology
- 40. AP Biology biosphere ecosystem community population Studying organisms in their environment organism
Notas do Editor
- Within a population’s geographic range, local densities may vary substantially. Variations in local density are among the most important characteristics that a population ecologist might study, since they provide insight into the environmental associations and social interactions of individuals in the population. Environmental differences—even at a local level—contribute to variation in population density; some habitat patches are simply more suitable for a species than are others. Social interactions between members of the population, which may maintain patterns of spacing between individuals, can also contribute to variation in population density.
- The most common pattern of dispersion is clumped, with the individuals aggregated in patches. Plants or fungi are often clumped where soil conditions and other environmental factors favor germination and growth. For example, mushrooms may be clumped on a rotting log. Many animals spend much of their time in a particular microenvironment that satisfies their requirements. Forest insects and salamanders, for instance, are frequently clumped under logs, where the humidity tends to be higher than in more exposed areas. Clumping of animals may also be associated with mating behavior. For example, mayflies often swarm in great numbers, a behavior that increases mating chances for these insects, which survive only a day or two as reproductive adults. Group living may also increase the effectiveness of certain predators; for example, a wolf pack is more likely than a single wolf to subdue a large prey animal, such as a moose
- A uniform, or evenly spaced, pattern of dispersion may result from direct interactions between individuals in the population. For example, some plants secrete chemicals that inhibit the germination and growth of nearby individuals that could compete for resources. Animals often exhibit uniform dispersion as a result of antagonistic social interactions, such as territoriality —the defense of a bounded physical space against encroachment by other individuals. Uniform patterns are not as common in populations as clumped patterns.
- A Type I curve is flat at the start, reflecting low death rates during early and middle life, then drops steeply as death rates increase among older age groups. Humans and many other large mammals that produce few offspring but provide them with good care often exhibit this kind of curve. In contrast, a Type III curve drops sharply at the start, reflecting very high death rates for the young, but then flattens out as death rates decline for those few individuals that have survived to a certain critical age. This type of curve is usually associated with organisms that produce very large numbers of offspring but provide little or no care, such as long–lived plants, many fishes, and marine invertebrates. An oyster, for example, may release millions of eggs, but most offspring die as larvae from predation or other causes. Those few that survive long enough to attach to a suitable substrate and begin growing a hard shell will probably survive for a relatively long time. Type II curves are intermediate, with a constant death rate over the organism’s life span. This kind of survivorship occurs in Belding’s ground squirrels and some other rodents, various invertebrates, some lizards, and some annual plants.
- A Type I curve is flat at the start, reflecting low death rates during early and middle life, then drops steeply as death rates increase among older age groups. Humans and many other large mammals that produce few offspring but provide them with good care often exhibit this kind of curve. In contrast, a Type III curve drops sharply at the start, reflecting very high death rates for the young, but then flattens out as death rates decline for those few individuals that have survived to a certain critical age. This type of curve is usually associated with organisms that produce very large numbers of offspring but provide little or no care, such as long–lived plants, many fishes, and marine invertebrates. An oyster, for example, may release millions of eggs, but most offspring die as larvae from predation or other causes. Those few that survive long enough to attach to a suitable substrate and begin growing a hard shell will probably survive for a relatively long time. Type II curves are intermediate, with a constant death rate over the organism’s life span. This kind of survivorship occurs in Belding’s ground squirrels and some other rodents, various invertebrates, some lizards, and some annual plants.
- The J–shaped curve of exponential growth is characteristic of some populations that are introduced into a new or unfilled environment or whose numbers have been drastically reduced by a catastrophic event and are rebounding. The graph illustrates the exponential population growth that occurred in the population of elephants in Kruger National Park, South Africa, after they were protected from hunting. After approximately 60 years of exponential growth, the large number of elephants had caused enough damage to the park vegetation that a collapse in the elephant food supply was likely, leading to an end to population growth through starvation. To protect other species and the park ecosystem before that happened, park managers began limiting the elephant population by using birth control and exporting elephants to other countries.
- Decrease rate of growth as N reaches K
- The population doubled to 1 billion within the next two centuries, doubled again to 2 billion between 1850 and 1930, and doubled still again by 1975 to more than 4 billion. The global population now numbers over 6 billion people and is increasing by about 73 million each year. The population grows by approximately 201,000 people each day, the equivalent of adding a city the size of Amarillo, Texas, or Madison, Wisconsin. Every week the population increases by the size of San Antonio, Milwaukee, or Indianapolis. It takes only four years for world population growth to add the equivalent of another United States. Population ecologists predict a population of 7.3–8.4 billion people on Earth by the year 2025.
- A more comprehensive approach to estimating the carrying capacity of Earth is to recognize that humans have multiple constraints: We need food, water, fuel, building materials, and other requisites, such as clothing and transportation. The ecological footprint concept summarizes the aggregate land and water area appropriated by each nation to produce all the resources it consumes and to absorb all the waste it generates. Six types of ecologically productive areas are distinguished in calculating the ecological footprint: arable land (land suitable for crops), pasture, forest, ocean, built–up land, and fossil energy land. (Fossil energy land is calculated on the basis of the land required for vegetation to absorb the CO2 produced by burning fossil fuels.) All measures are converted to land area as hectares (ha) per person (1 ha = 2.47 acres). Adding up all the ecologically productive land on the planet yields about 2 ha per person. Reserving some land for parks and conservation means reducing this allotment to 1.7 ha per person—the benchmark for comparing actual ecological footprints. The graph is the ecological footprints for 13 countries and for the whole world as of 1997. We can draw two key conclusions from the graph. First, countries vary greatly in their individual footprint size and in their available ecological capacity (the actual resource base of each country). The United States has an ecological footprint of 8.4 ha per person but has only 6.2 ha per person of available ecological capacity. In other words, the U.S. population is already above carrying capacity. By contrast, New Zealand has a larger ecological footprint of 9.8 ha per person but an available capacity of 14.3 ha per person, so it is below its carrying capacity. The second conclusion is that, in general, the world was already in ecological deficit when the study was conducted. The overall analysis suggests that the world is now at or slightly above its carrying capacity.
- A more comprehensive approach to estimating the carrying capacity of Earth is to recognize that humans have multiple constraints: We need food, water, fuel, building materials, and other requisites, such as clothing and transportation. The ecological footprint concept summarizes the aggregate land and water area appropriated by each nation to produce all the resources it consumes and to absorb all the waste it generates. Six types of ecologically productive areas are distinguished in calculating the ecological footprint: arable land (land suitable for crops), pasture, forest, ocean, built–up land, and fossil energy land. (Fossil energy land is calculated on the basis of the land required for vegetation to absorb the CO2 produced by burning fossil fuels.) All measures are converted to land area as hectares (ha) per person (1 ha = 2.47 acres). Adding up all the ecologically productive land on the planet yields about 2 ha per person. Reserving some land for parks and conservation means reducing this allotment to 1.7 ha per person—the benchmark for comparing actual ecological footprints. The graph is the ecological footprints for 13 countries and for the whole world as of 1997. We can draw two key conclusions from the graph. First, countries vary greatly in their individual footprint size and in their available ecological capacity (the actual resource base of each country). The United States has an ecological footprint of 8.4 ha per person but has only 6.2 ha per person of available ecological capacity. In other words, the U.S. population is already above carrying capacity. By contrast, New Zealand has a larger ecological footprint of 9.8 ha per person but an available capacity of 14.3 ha per person, so it is below its carrying capacity. The second conclusion is that, in general, the world was already in ecological deficit when the study was conducted. The overall analysis suggests that the world is now at or slightly above its carrying capacity.