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Biology in Focus - Chapter 40

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Biology in Focus - Chapter 40 - Population Ecology and the Distribution of Organisms

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Biology in Focus - Chapter 40

  1. 1. CAMPBELL BIOLOGY IN FOCUS © 2014 Pearson Education, Inc. Urry • Cain • Wasserman • Minorsky • Jackson • Reece Lecture Presentations by Kathleen Fitzpatrick and Nicole Tunbridge 40 Population Ecology and the Distribution of Organisms
  2. 2. © 2014 Pearson Education, Inc. Overview: Discovering Ecology  Ecology is the scientific study of the interactions between organisms and the environment  These interactions determine the distribution of organisms and their abundance  Modern ecology includes observation and experimentation
  3. 3. © 2014 Pearson Education, Inc.  The rediscovery of the nearly extinct harlequin toad in Costa Rica raises many ecological questions  What environmental factors limit their geographic distribution?  What factors (food, pathogens) affect population size?
  4. 4. © 2014 Pearson Education, Inc. Figure 40.1
  5. 5. © 2014 Pearson Education, Inc. Figure 40.2 Global ecology Landscape ecology Ecosystem ecology Community ecology Population ecology Organismal ecology
  6. 6. © 2014 Pearson Education, Inc.  Global ecology is concerned with the biosphere, or global ecosystem, which is the sum of all the planet’s ecosystems  Global ecology examines the influence of energy and materials on organisms across the biosphere
  7. 7. © 2014 Pearson Education, Inc. Figure 40.2a Global ecology
  8. 8. © 2014 Pearson Education, Inc.  Landscape ecology focuses on the exchanges of energy, materials, and organisms across multiple ecosystems  A landscape (or seascape) is a mosaic of connected ecosystems
  9. 9. © 2014 Pearson Education, Inc. Figure 40.2b Landscape ecology
  10. 10. © 2014 Pearson Education, Inc.  Ecosystem ecology emphasizes energy flow and chemical cycling among the various biotic and abiotic components  An ecosystem is the community of organisms in an area and the physical factors with which they interact
  11. 11. © 2014 Pearson Education, Inc. Figure 40.2c Ecosystem ecology
  12. 12. © 2014 Pearson Education, Inc.  Community ecology deals with the whole array of interacting species in a community  A community is a group of populations of different species in an area
  13. 13. © 2014 Pearson Education, Inc. Figure 40.2d Community ecology
  14. 14. © 2014 Pearson Education, Inc.  Population ecology focuses on factors affecting population size over time  A population is a group of individuals of the same species living in an area
  15. 15. © 2014 Pearson Education, Inc. Figure 40.2e Population ecology
  16. 16. © 2014 Pearson Education, Inc.  Organismal ecology studies how an organism’s structure, physiology, and (for animals) behavior meet environmental challenges  Organismal ecology includes physiological, evolutionary, and behavioral ecology
  17. 17. © 2014 Pearson Education, Inc. Figure 40.2f Organismal ecology
  18. 18. © 2014 Pearson Education, Inc. Concept 40.1: Earth’s climate influences the structure and distribution of terrestrial biomes  The long-term prevailing weather conditions in an area constitute its climate  Four major abiotic components of climate are temperature, precipitation, sunlight, and wind
  19. 19. © 2014 Pearson Education, Inc.  Abiotic factors are the nonliving chemical and physical attributes of the environment  Biotic factors are the other organisms that make up the living component of the environment  Macroclimate consists of patterns on the global, regional, and landscape level
  20. 20. © 2014 Pearson Education, Inc. Global Climate Patterns  Global climate patterns are determined largely by solar energy and the planet’s movement in space  The warming effect of the sun causes temperature variations, which drive evaporation and the circulation of air and water  This causes latitudinal variations in climate
  21. 21. © 2014 Pearson Education, Inc.  Latitudinal variation in sunlight intensity is caused by the curved shape of Earth  Sunlight strikes the tropics, regions between 23.5° north and 23.5° south latitude, most directly  At higher latitudes, where sunlight strikes Earth at an oblique angle, light is more diffuse
  22. 22. © 2014 Pearson Education, Inc. Figure 40.3a Atmosphere Low angle of incoming sunlight Sun overhead at equinoxes Low angle of incoming sunlight Latitudinal variation in sunlight intensity 90°S (South Pole) 0° (Equator) 23.5°S (Tropic of Capricorn) 90°N (North Pole) 23.5°N (Tropic of Cancer)
  23. 23. © 2014 Pearson Education, Inc.  Global air circulation and precipitation patterns are initiated by intense solar radiation near the equator  Warm, wet air rising near the equator creates precipitation in the tropics  Dry air descending at 30° north and south latitudes causes desert conditions  This pattern of precipitation and drying is repeated at the 60° north and south latitudes and the poles
  24. 24. © 2014 Pearson Education, Inc. Figure 40.3b Global air circulation and precipitation patterns 30°N Northeast trades 66.5°N (Arctic Circle) 30°S 60°S Southeast trades Westerlies 0° 66.5°S (Antarctic Circle) 30°N 60°N Westerlies Ascending moist air releases moisture. 0° Descending dry air absorbs moisture.
  25. 25. © 2014 Pearson Education, Inc.  Variation in the speed of Earth’s rotation at different latitudes results in the major wind patterns  Trade winds blow east to west in the tropics  Westerlies blow west to east in temperate zones
  26. 26. © 2014 Pearson Education, Inc. Figure 40.3ba Northeast trades 66.5°N (Arctic Circle) 30°S 60°S Southeast trades Westerlies 0° 66.5°S (Antarctic Circle) 30°N 60°N Westerlies Global air circulation and precipitation patterns
  27. 27. © 2014 Pearson Education, Inc. Figure 40.3bb Global air circulation and precipitation patterns 30°N Ascending moist air releases moisture. 0° Descending dry air absorbs moisture.
  28. 28. © 2014 Pearson Education, Inc. Regional Effects on Climate  Climate is affected by seasonality, large bodies of water, and mountains
  29. 29. © 2014 Pearson Education, Inc. Seasonality  Seasonal variations of light and temperature increase steadily toward the poles  Seasonality at high latitudes is caused by the tilt of Earth’s axis of rotation and its annual passage around the sun  Belts of wet and dry air straddling the equator shift throughout the year with the changing angle of the sun  Changing wind patterns affect ocean currents
  30. 30. © 2014 Pearson Education, Inc. Figure 40.4 Constant tilt of 23.5° June solstice 30°N December solstice September equinox 60°N 0° (equator) 30°S March equinox
  31. 31. © 2014 Pearson Education, Inc. Bodies of Water  Oceans, their currents, and large lakes moderate the climate of nearby terrestrial environments  The California Current carries cold water southward along western North America  The Gulf Stream carries warm water from the equator to the North Atlantic
  32. 32. © 2014 Pearson Education, Inc. Figure 40.5 California Current PACIFIC OCEAN Gulf Stream ATLANTIC OCEAN Labrador Current
  33. 33. © 2014 Pearson Education, Inc.  During the day, air rises over warm land and draws a cool breeze from the water across the land  As the land cools at night, air rises over the warmer water and draws cooler air from land back over the water, which is replaced by warmer air from offshore
  34. 34. © 2014 Pearson Education, Inc. Figure 40.6 Mountain range Air flow Ocean Leeward side of mountains
  35. 35. © 2014 Pearson Education, Inc. Mountains  Rising air releases moisture on the windward side of a peak and creates a “rain shadow” as it absorbs moisture on the leeward side  Many deserts are found in the “rain shadow” of mountains
  36. 36. © 2014 Pearson Education, Inc.  Mountains affect the amount of sunlight reaching an area  In the Northern Hemisphere, south-facing slopes receive more sunlight than north-facing slopes  Every 1,000-m increase in elevation produces a temperature drop of approximately 6°C
  37. 37. © 2014 Pearson Education, Inc.  Biomes are major life zones characterized by vegetation type (terrestrial biomes) or physical environment (aquatic biomes)  Climate is very important in determining why terrestrial biomes are found in certain areas  Climate affects the latitudinal patterns of terrestrial biomes Climate and Terrestrial Biomes
  38. 38. © 2014 Pearson Education, Inc. Figure 40.7 Temperate broadleaf forest 30°S Equator Tropic of Capricorn 30°N Tropic of Cancer Northern coniferous forest High mountains Tundra Polar ice Tropical forest Savanna Chaparral Desert Temperate grassland
  39. 39. © 2014 Pearson Education, Inc.  A climograph plots 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
  40. 40. © 2014 Pearson Education, Inc. Figure 40.8 Temperate broadleaf forest Northern coniferous forest Annual mean precipitation (cm) −15 Tropical forestDesert Temperate grassland Arctic and alpine tundra Annualmeantemperature(°C) 15 0 0 30 100 200 300 400
  41. 41. © 2014 Pearson Education, Inc.  Natural and human-caused disturbances alter the distribution of biomes  A disturbance is an event that changes a community by removing organisms and altering resource availability  For example, frequent fires kill woody plants preventing woodlands from establishing
  42. 42. © 2014 Pearson Education, Inc. General Features of Terrestrial Biomes  Terrestrial biomes are often named for major physical or climatic factors and for vegetation  Terrestrial biomes usually grade into each other, without sharp boundaries  The area of intergradation, called an ecotone, may be wide or narrow
  43. 43. © 2014 Pearson Education, Inc.  Vertical layering is an important feature of terrestrial biomes, and in a forest it might consist of an upper canopy, low-tree layer, shrub understory, ground layer of herbaceous plants, forest floor, and root layer  Layering of vegetation provides diverse habitats for animals
  44. 44. © 2014 Pearson Education, Inc.  Terrestrial biomes can be characterized by distribution, precipitation, temperature, plants, and animals
  45. 45. © 2014 Pearson Education, Inc.  Tropical forest occurs in equatorial and subequatorial regions  Temperature is high year-round (25–29°C) with little seasonal variation  In tropical rain forests, rainfall is relatively constant, while in tropical dry forests precipitation is highly seasonal
  46. 46. © 2014 Pearson Education, Inc. Figure 40.9a A tropical rain forest in Costa Rica
  47. 47. © 2014 Pearson Education, Inc.  Tropical forests are vertically layered, and competition for light is intense  Tropical forests are home to millions of animal species, including an estimated 5–30 million still undescribed species of insects, spiders, and other arthropods  Rapid human population growth is now destroying many tropical forests
  48. 48. © 2014 Pearson Education, Inc.  Savanna occurs in equatorial and subequatorial regions  Precipitation is seasonal  Temperature averages 24–29°C but is more seasonally variable than in the tropics
  49. 49. © 2014 Pearson Education, Inc. Figure 40.9b A savanna in Kenya
  50. 50. © 2014 Pearson Education, Inc.  Grasses and forbs make up most of the ground cover  The dominant plant species are fire-adapted and tolerant of seasonal drought  Common inhabitants include insects and mammals such as wildebeests, zebras, lions, and hyenas  Fires set by humans may help maintain this biome
  51. 51. © 2014 Pearson Education, Inc.  Deserts occur in bands near 30° north and south of the equator and in the interior of continents  Precipitation is low and highly variable, generally less than 30 cm per year  Deserts may be hot (>50°C) or cold (–30°C) with seasonal and daily temperature variation
  52. 52. © 2014 Pearson Education, Inc. Figure 40.9c Organ Pipe Cactus National Monument, Arizona
  53. 53. © 2014 Pearson Education, Inc.  Desert plants are adapted for heat and desiccation tolerance, water storage, and reduced leaf surface area  Common desert animals include scorpions, ants, beetles, snakes, lizards, migratory and resident birds, and seed-eating rodents; many are nocturnal  Urbanization and conversion to irrigated agriculture have reduced the natural biodiversity of some deserts
  54. 54. © 2014 Pearson Education, Inc.  Chaparral occurs in midlatitude coastal regions on several continents  Precipitation is highly seasonal with rainy winters and dry summers  Summer is hot (30°C); fall, winter, and spring are cool (10–12°C)
  55. 55. © 2014 Pearson Education, Inc. Figure 40.9d An area of chaparral in California
  56. 56. © 2014 Pearson Education, Inc.  The chaparral is dominated by shrubs and small trees; many plants are adapted to fire and drought  Animals include browsing mammals, insects, amphibians, small mammals, and birds  Humans have reduced chaparral areas through agriculture and urbanization
  57. 57. © 2014 Pearson Education, Inc.  Temperate grasslands occur at midlatitudes, often in the interior of continents  Precipitation is highly seasonal  Winters are cold (often below −10°C) and dry; summers are hot (often near 30°C) and wet
  58. 58. © 2014 Pearson Education, Inc. Figure 40.9e A grassland in Mongolia
  59. 59. © 2014 Pearson Education, Inc.  The dominant plants, grasses and forbs, are adapted to droughts and fire  Native mammals include large grazers such as bison and wild horses and small burrowers such as prairie dogs  Most grasslands have been converted to farmland
  60. 60. © 2014 Pearson Education, Inc.  Northern coniferous forest, or taiga, spans northern North America and Eurasia and is the largest terrestrial biome on Earth  Precipitation ranges from 30–70 cm  Winters are cold; summers may be hot (e.g., Siberia ranges from −50°C to 20°C)
  61. 61. © 2014 Pearson Education, Inc. Figure 40.9f A coniferous forest in Norway
  62. 62. © 2014 Pearson Education, Inc.  Conifers such as pine, spruce, fir, and hemlock dominate  The conical shape of conifers prevents too much snow from accumulating and breaking their branches  Animals include migratory and resident birds and large mammals such as moose, brown bears, and Siberian tigers  Periodic insect outbreaks kill vast tracts of trees  Some forests are being logged at an alarming rate
  63. 63. © 2014 Pearson Education, Inc.  Temperate broadleaf forest is found at midlatitudes in the Northern Hemisphere, with smaller areas in Chile, South Africa, Australia, and New Zealand  Significant amounts of precipitation fall during all seasons as rain or snow  Winters average 0°C; summers are hot and humid (near 35°C)
  64. 64. © 2014 Pearson Education, Inc. Figure 40.9g A temperate broadleaf forest in New Jersey
  65. 65. © 2014 Pearson Education, Inc.  Dominant plants include deciduous trees in the Northern Hemisphere and evergreen eucalyptus in Australia  In the Northern Hemisphere, many mammals hibernate in the winter; birds migrate to warmer areas  These forests have been heavily settled on all continents but are recovering in places
  66. 66. © 2014 Pearson Education, Inc.  Tundra covers expansive areas of the Arctic; alpine tundra exists on high mountaintops at all latitudes  Precipitation is low in arctic tundra and higher in alpine tundra  Winters are cold (below −30°C); summers are relatively cool (less than 10°C)
  67. 67. © 2014 Pearson Education, Inc. Figure 40.9h Dovrefjell National Park, Norway
  68. 68. © 2014 Pearson Education, Inc.  Vegetation is herbaceous (mosses, grasses, forbs, dwarf shrubs, trees, and lichen)  Permafrost, a permanently frozen layer of soil, restricts growth of plant roots  Mammals include musk oxen, caribou, reindeer, bears, wolves, and foxes; many migratory bird species nest in the summer  Settlement is sparse, but tundra has become the focus of oil and mineral extraction
  69. 69. © 2014 Pearson Education, Inc. Concept 40.2: Aquatic biomes are diverse and dynamic systems that cover most of Earth  Aquatic biomes account for the largest part of the biosphere in terms of area  They show less latitudinal variation than terrestrial biomes  Marine biomes have salt concentrations of about 3%  The largest marine biome is made of oceans, which cover about 75% of Earth’s surface and have an enormous impact on the biosphere
  70. 70. © 2014 Pearson Education, Inc.  Freshwater biomes have salt concentrations of less than 0.1%  Freshwater biomes are closely linked to soils and the biotic components of the surrounding terrestrial biome
  71. 71. © 2014 Pearson Education, Inc. Video: Clownfish Anemone Video: Coral Reef Video: Hydrothermal Vent Video: Shark Eating a Seal Video: Swans Taking Flight Video: Tubeworms
  72. 72. © 2014 Pearson Education, Inc.  Aquatic biomes can be characterized by their physical and chemical environment, geological features, photosynthetic organisms, and heterotrophs
  73. 73. © 2014 Pearson Education, Inc.  Wetlands and estuaries are among the most productive habitats on Earth  Wetlands are inundated by water at least sometimes and support plants adapted to water-saturated soil  An estuary is a transition area between river and sea; salinity varies with the rise and fall of the tides  High organic production and decomposition in these biomes result in low levels of dissolved oxygen
  74. 74. © 2014 Pearson Education, Inc. Figure 40.10a A basin wetland in the United Kingdom
  75. 75. © 2014 Pearson Education, Inc.  Wetlands can develop in shallow basins, along flooded river banks, or on the coasts of large lakes  Estuaries include a complex network of tidal channels, islands, and mudflats  Plants are adapted to growing in periodically anaerobic, water-saturated soils  Wetland plants include cattails and sedges; estuaries are characterized by saltmarsh grasses
  76. 76. © 2014 Pearson Education, Inc.  Wetlands are home to diverse invertebrates and birds, as well as frogs and alligators  Estuaries support an abundance of marine invertebrates, fish, waterfowl, and marine mammals  Humans activities have destroyed up to 90% of wetlands and disrupted estuaries worldwide
  77. 77. © 2014 Pearson Education, Inc.  Lakes vary in size from small ponds to very large lakes  Temperate lakes may have a seasonal thermocline; tropical lowland lakes have a year-round thermocline  Oligotrophic lakes are nutrient-poor and generally oxygen-rich  Eutrophic lakes are nutrient-rich and often depleted of oxygen if ice covered in winter
  78. 78. © 2014 Pearson Education, Inc. Figure 40.10b An oligotrophic lake in Alberta, Canada
  79. 79. © 2014 Pearson Education, Inc.  Eutrophic lakes have more surface area relative to depth than oligotrophic lakes  Rooted and floating aquatic plants live in the shallow and well-lighted littoral zone close to shore  Water is too deep in the limnetic zone to support rooted aquatic plants; the primary producers are phytoplankton
  80. 80. © 2014 Pearson Education, Inc.  Zooplankton are drifting heterotrophs that graze on the phytoplankton  Invertebrates live in the benthic zone  Fishes live in all zones with sufficient oxygen  Human-induced nutrient enrichment can lead to algal blooms, oxygen depletion, and fish kills
  81. 81. © 2014 Pearson Education, Inc.  Streams and rivers have varying environmental conditions from headwater to mouth  Headwater streams are generally cold, clear, turbulent, swift, and oxygen-rich; they are often narrow and rocky  Downstream waters form rivers and are generally warmer and more turbid; they are often wide and meandering and have silty bottoms  Salt and nutrients increase from headwaters to mouth; oxygen content decreases from headwaters to mouth
  82. 82. © 2014 Pearson Education, Inc. Figure 40.10c A headwater stream in Washington
  83. 83. © 2014 Pearson Education, Inc.  Headwater streams may be rich in phytoplankton or rooted aquatic plants  A diversity of fishes and invertebrates inhabit unpolluted rivers and streams  Pollution degrades water quality and kills aquatic organisms  Dams impair natural flow of stream and river ecosystems
  84. 84. © 2014 Pearson Education, Inc.  Intertidal zones are periodically submerged and exposed by the tides  Intertidal organisms are challenged by variations in temperature and salinity and by the mechanical forces of wave action  Oxygen and nutrient levels are high  Substrate varies from rocky to sandy
  85. 85. © 2014 Pearson Education, Inc. Figure 40.10d A rocky intertidal zone on the Oregon coast
  86. 86. © 2014 Pearson Education, Inc.  Protected sandy zones support sea grass and algae; rocky zones support attached marine algae  In rocky zones, many animals have structural adaptations for attaching to rock  In sandy zones, worms, clams, and crustaceans bury themselves in sand  Other animals include sponges, sea anemones, and small fishes  Oil pollution has disrupted many intertidal areas
  87. 87. © 2014 Pearson Education, Inc.  Coral reefs are formed from the calcium carbonate skeletons of corals (cnidarians)  Shallow reef-building corals live in the photic zone in warm (about 20–30°C), clear water; deep-sea corals live at depths of 200–1,500 m  Corals require high oxygen concentrations and a solid substrate for attachment  A coral reef progresses from a fringing reef to a barrier reef to a coral atoll
  88. 88. © 2014 Pearson Education, Inc. Figure 40.10e A coral reef in the Red Sea
  89. 89. © 2014 Pearson Education, Inc.  Corals are the predominant animals on the reef  They form mutualisms with symbiotic algae that provide them organic molecules  A high diversity of fish and invertebrates inhabit coral reefs  Coral collection, overfishing, global warming, and pollution all contribute to reduction in coral populations
  90. 90. © 2014 Pearson Education, Inc.  The oceanic pelagic zone is constantly mixed by wind-driven oceanic currents  Oxygen levels are high  Turnover in temperate oceans renews nutrients in the photic zones  This biome covers approximately 70% of Earth’s surface
  91. 91. © 2014 Pearson Education, Inc. Figure 40.10f Open ocean near Iceland
  92. 92. © 2014 Pearson Education, Inc.  Phytoplankton and zooplankton are the dominant organisms in this biome; also found are free- swimming animals  Zooplankton includes protists, worms, krill, jellies, and invertebrate larvae  Other animals include squids, fishes, sea turtles, and marine mammals  Overfishing has depleted fish stocks  Humans have polluted oceans with dumping of waste
  93. 93. © 2014 Pearson Education, Inc.  The marine benthic zone consists of the seafloor  Organisms in the very deep benthic (abyssal) zone are adapted to continuous cold and high water pressure  Substrate is mainly soft sediments; some areas are rocky
  94. 94. © 2014 Pearson Education, Inc.  Shallow areas contain seaweeds and filamentous algae  In dark, hot environments near deep-sea hydrothermal vents of volcanic origin, the food producers are chemoautotrophic prokaryotes  Giant tube worms, arthropods, and echinoderms are abundant heterotrophs near hydrothermal vents
  95. 95. © 2014 Pearson Education, Inc. Figure 40.10g A deep-sea hydrothermal vent community
  96. 96. © 2014 Pearson Education, Inc.  Coastal benthic communities include invertebrates and fishes  Overfishing and dumping of organic waste have depleted fish populations
  97. 97. © 2014 Pearson Education, Inc. Zonation in Aquatic Biomes  Many aquatic biomes are stratified into zones or layers defined by light penetration, temperature, and depth  The upper photic zone has sufficient light for photosynthesis, while the lower aphotic zone receives little light  The photic and aphotic zones make up the pelagic zone
  98. 98. © 2014 Pearson Education, Inc.  The organic and inorganic sediment at the bottom of all aquatic zones is called the benthic zone  The communities of organisms in the benthic zone are collectively called the benthos
  99. 99. © 2014 Pearson Education, Inc. Figure 40.11 Zonation in a lake Littoral zone Limnetic zone Pelagic zone Photic zone Aphotic zone Benthic zone
  100. 100. © 2014 Pearson Education, Inc.  In oceans and most lakes, a temperature boundary called the thermocline separates the warm upper layer from the cold deeper water
  101. 101. © 2014 Pearson Education, Inc.  Communities in aquatic biomes vary with depth, light penetration, distance from shore, and position in the pelagic or benthic zone  Most organisms occur in the relatively shallow photic zone  The aphotic zone in oceans is extensive but harbors little life
  102. 102. © 2014 Pearson Education, Inc. Concept 40.3: Interactions between organisms and the environment limit the distribution of species  Species distributions are the result of ecological and evolutionary interactions through time  Ecological time is the minute-to-minute time frame of interactions between organisms and the environment  Evolutionary time spans many generations and captures adaptation through natural selection
  103. 103. © 2014 Pearson Education, Inc.  Events in ecological time can lead to evolution  For example, Galápagos finches with larger beaks were more likely to survive a drought, as they could eat the available larger seeds  As a result, the average beak size was larger in the next generation  This resulted in an evolutionary change
  104. 104. © 2014 Pearson Education, Inc.  Ecologists ask questions about where species occur and why species occur where they do
  105. 105. © 2014 Pearson Education, Inc. Figure 40.12-1 Why is species X absent from an area? Does dispersal limit its distribution? Area inaccessible or insufficient time Do biotic factors (other species) limit its distribution? Yes No
  106. 106. © 2014 Pearson Education, Inc. Figure 40.12-2 Why is species X absent from an area? Does dispersal limit its distribution? Area inaccessible or insufficient time Predation, parasitism, competition, disease Do biotic factors (other species) limit its distribution? Do abiotic factors limit its distribution? Yes No Yes No
  107. 107. © 2014 Pearson Education, Inc. Figure 40.12-3 Chemical factors Why is species X absent from an area? Does dispersal limit its distribution? Area inaccessible or insufficient time Predation, parasitism, competition, disease Water, oxygen, salinity, pH, soil nutrients, etc. Do biotic factors (other species) limit its distribution? Temperature, light, soil structure, fire, moisture, etc. Do abiotic factors limit its distribution? Physical factors Yes No Yes No
  108. 108. © 2014 Pearson Education, Inc. Dispersal and Distribution  Dispersal is the movement of individuals away from centers of high population density or from their area of origin  Dispersal contributes to the global distribution of organisms
  109. 109. © 2014 Pearson Education, Inc.  Transplants indicate if dispersal is a key factor limiting species distributions  Transplants include organisms that are intentionally or accidentally relocated from their original distribution  If a transplant is successful, it indicates that the species’ potential range is larger than its actual range  Species transplants can disrupt the communities or ecosystems to which they have been introduced
  110. 110. © 2014 Pearson Education, Inc. Biotic Factors  Biotic factors that affect the distribution of organisms may include  Predation  Herbivory  For example, sea urchins can limit the distribution of seaweeds  Mutualism  Parasitism  Competition
  111. 111. © 2014 Pearson Education, Inc. Figure 40.13 Control (both urchins and limpets present) 100 Both limpets and urchins removed Only urchins removed Only limpets removed Limpet Sea urchin August 1982 August 1983 February 1983 February 1984 80 60 40 20 0 Seaweedcover(%) Results
  112. 112. © 2014 Pearson Education, Inc. Abiotic Factors  Abiotic factors affecting the distribution of organisms include  Temperature  Water and oxygen  Salinity  Sunlight  Rocks and soil
  113. 113. © 2014 Pearson Education, Inc.  Temperature is an important environmental factor in the 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  Most organisms function best within a specific temperature range
  114. 114. © 2014 Pearson Education, Inc.  Availability of water and oxygen is an important factor in species distribution  Desert organisms exhibit adaptations for water conservation  Water affects oxygen availability, as oxygen diffuses slowly in water  Oxygen concentrations can be low in deep oceans and deep lakes
  115. 115. © 2014 Pearson Education, Inc.  Salinity, salt concentration, affects the water balance of organisms through osmosis  Most aquatic organisms are restricted to either freshwater or saltwater habitats  Few terrestrial organisms are adapted to high- salinity habitats
  116. 116. © 2014 Pearson Education, Inc.  Sunlight is the energy source for photosynthetic organisms and, as such, can limit their distribution  In aquatic environments most photosynthesis occurs near the surface where sunlight is available  Shading by the canopy drives intense competition for light in forests
  117. 117. © 2014 Pearson Education, Inc.  Rocks and soil have many characteristics that limit the distribution of plants and thus the animals that feed on them  Physical structure  pH  Mineral composition
  118. 118. © 2014 Pearson Education, Inc. Concept 40.4: Dynamic biological processes influence population density, dispersion, and demographics  Population ecology explores how biotic and abiotic factors influence density, distribution, and size of populations  A population is a group of individuals of a single species living in the same general area  Populations are described by their boundaries and size
  119. 119. © 2014 Pearson Education, Inc. 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
  120. 120. © 2014 Pearson Education, Inc. 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 density can be estimated by extrapolation from small samples or an index of population size (e.g., number of nests)
  121. 121. © 2014 Pearson Education, Inc.  Density is the result of an interplay between processes that add individuals to a population and those that remove individuals  Additions occur through birth and immigration, the influx of new individuals from other areas  Removal of individuals occurs through death and emigration, the movement of individuals out of a population
  122. 122. © 2014 Pearson Education, Inc. Figure 40.14 Births and immigration add individuals to a population. Deaths and emigration remove individuals from a population. Births Immigration Deaths Emigration
  123. 123. © 2014 Pearson Education, Inc. Patterns of Dispersion  Environmental and social factors influence the spacing of individuals in a population  The most common pattern of dispersion is clumped, in which individuals aggregate in patches  A clumped dispersion may be influenced by resource availability and behavior
  124. 124. © 2014 Pearson Education, Inc. Figure 40.15 (a) Clumped (c) Random(b) Uniform
  125. 125. © 2014 Pearson Education, Inc. Figure 40.15a (a) Clumped
  126. 126. © 2014 Pearson Education, Inc. Figure 40.15b (b) Uniform
  127. 127. © 2014 Pearson Education, Inc. Figure 40.15c (c) Random
  128. 128. © 2014 Pearson Education, Inc. Figure 40.15d (a) Clumped (c) Random(b) Uniform
  129. 129. © 2014 Pearson Education, Inc.  A uniform dispersion is one in which individuals are evenly distributed  It may be influenced by social interactions such as territoriality, the defense of a bounded space against other individuals
  130. 130. © 2014 Pearson Education, Inc.  In a random dispersion, the position of each individual is independent of other individuals  It occurs in the absence of strong attractions or repulsions
  131. 131. © 2014 Pearson Education, Inc. 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
  132. 132. © 2014 Pearson Education, Inc. Life Tables  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, from birth to death
  133. 133. © 2014 Pearson Education, Inc. Survivorship Curves  A survivorship curve is a graphic way of representing the data in a life table  Survivorship curves plot the proportion or numbers of a cohort still alive at each age
  134. 134. © 2014 Pearson Education, Inc.  Survivorship curves can be classified into three general types  Type I: low death rates during early and middle life and an increase in death rates among older age groups  Type II: a constant death rate over the organism’s life span  Type III: high death rates for the young and a lower death rate for survivors  Many species are intermediate to these curves
  135. 135. © 2014 Pearson Education, Inc. Figure 40.16 1,000 Percentage of maximum life span III Numberofsurvivors(logscale) 100 10 0 1 10050 II I
  136. 136. © 2014 Pearson Education, Inc. Reproductive Rates  For species with sexual reproduction, demographers often concentrate on females in a population  A reproductive table, or fertility schedule, is an age-specific summary of the reproductive rates in a population  It describes the reproductive patterns of a population
  137. 137. © 2014 Pearson Education, Inc. Table 40.1
  138. 138. © 2014 Pearson Education, Inc. Concept 40.5: The exponential and logistic models describe the growth of populations  Unlimited growth occurs under ideal conditions; in nature, growth is limited by various factors  Ecologists study growth in both idealized and realistic conditions
  139. 139. © 2014 Pearson Education, Inc. Per Capita Rate of Increase  Change in population size can be defined by the equation  If immigration and emigration are ignored, a population’s growth rate (per capita increase) equals birth rate minus death rate − − Change in population size Births Immigrants entering population Deaths Emigrants leaving population = +
  140. 140. © 2014 Pearson Education, Inc.  The population growth rate can be expressed mathematically as where ∆N is the change in population size, ∆t is the time interval, B is the number of births, and D is the number of deaths ΔN Δt = B −D
  141. 141. © 2014 Pearson Education, Inc.  Births and deaths can be expressed as the average number of births and deaths per individual during the specified time interval where b is the annual per capita birth rate, m (for mortality) is the per capita death rate, and N is population size B = bN D = mN
  142. 142. © 2014 Pearson Education, Inc.  The population growth equation can be revised ΔN Δt = bN −mN
  143. 143. © 2014 Pearson Education, Inc.  The per capita rate of increase (r) is given by r = b − m  Zero population growth (ZPG) occurs when the birth rate equals the death rate (r = 0)
  144. 144. © 2014 Pearson Education, Inc.  Change in population size can now be written as ΔN Δt = rN
  145. 145. © 2014 Pearson Education, Inc.  Instantaneous growth rate can be expressed as where rinst is the instantaneous per capita rate of increase dN dt = rinstN
  146. 146. © 2014 Pearson Education, Inc. Exponential Growth  Exponential population growth is population increase under idealized conditions  Under these conditions, the rate of increase is at its maximum, denoted as rmax  The equation of exponential population growth is dN dt = rmaxN
  147. 147. © 2014 Pearson Education, Inc.  Exponential population growth results in a J-shaped curve
  148. 148. © 2014 Pearson Education, Inc. Figure 40.17 1,000 Number of generations Populationsize(N) = 1.0N 10 0 0 155 2,000 1,500 500 = 0.5N dt dN dt dN
  149. 149. © 2014 Pearson Education, Inc.  The J-shaped curve of exponential growth characterizes populations in new environments or rebounding populations  For example, the elephant population in Kruger National Park, South Africa, grew exponentially after hunting was banned
  150. 150. © 2014 Pearson Education, Inc. Figure 40.18 6,000 Year Elephantpopulation 0 2,000 8,000 4,000 1900 1930 1940 1950 1960 19701910 1920
  151. 151. © 2014 Pearson Education, Inc. Figure 40.18a
  152. 152. © 2014 Pearson Education, Inc. 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  Carrying capacity varies with the abundance of limiting resources
  153. 153. © 2014 Pearson Education, Inc. The Logistic Growth Model  In the logistic population growth model, the per capita rate of increase declines as carrying capacity is reached  The logistic model starts with the exponential model and adds an expression that reduces per capita rate of increase as N approaches K dN dt = rmaxN (K −N) K
  154. 154. © 2014 Pearson Education, Inc. Table 40.2
  155. 155. © 2014 Pearson Education, Inc.  The logistic model of population growth produces a sigmoid (S-shaped) curve
  156. 156. © 2014 Pearson Education, Inc. Figure 40.19 1,000 Number of generations Populationsize(N) = 1.0N 10 0 0 155 2,000 1,500 500 = 1.0N dt dN Exponential growth Population growth begins slowing here. K = 1,500 dt dN (1,500 − N) 1,500 Logistic growth
  157. 157. © 2014 Pearson Education, Inc. The Logistic Model and Real Populations  The growth of many laboratory populations, including paramecia, fits an S-shaped curve when resources are limited  These organisms are grown in a constant environment lacking predators and competitors Animation: Population Ecology
  158. 158. © 2014 Pearson Education, Inc. Figure 40.20 1,000 Time (days) NumberofParamecium/mL 10 0 0 155 (a) A Paramecium population in the lab 800 200 400 600 Time (days) 140 0 0 160 30 (b) A Daphnia (water flea) population in the lab 40 6020 100 12080NumberofDaphnia/50mL 180 60 150 120 90
  159. 159. © 2014 Pearson Education, Inc. Figure 40.20a 1,000 Time (days) Numberof Paramecium/mL 10 0 0 155 (a) A Paramecium population in the lab 800 200 400 600
  160. 160. © 2014 Pearson Education, Inc. Figure 40.20b Time (days) 140 0 0 160 30 (b) A Daphnia (water flea) population in the lab 40 6020 100 12080 Numberof Daphnia/50mL 180 60 150 120 90
  161. 161. © 2014 Pearson Education, Inc.  Some populations overshoot K before settling down to a relatively stable density  Some populations fluctuate greatly and make it difficult to define K
  162. 162. © 2014 Pearson Education, Inc.  The logistic model fits few real populations but is useful for estimating possible growth  Conservation biologists can use the model to estimate the critical size below which populations may become extinct
  163. 163. © 2014 Pearson Education, Inc. Concept 40.6: Population dynamics are influenced strongly by life history traits and population density  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
  164. 164. © 2014 Pearson Education, Inc. “Trade-offs” and Life Histories  Organisms have finite resources, which may lead to trade-offs between survival and reproduction  Selective pressures influence the trade-off between the number and size of offspring  Some plants produce a large number of small seeds, ensuring that at least some of them will grow and eventually reproduce
  165. 165. © 2014 Pearson Education, Inc. Figure 40.21 Dandelions grow quickly and release a large number of tiny fruits. The Brazil nut tree (above), produces a moderate number of large seeds in pods (left).
  166. 166. © 2014 Pearson Education, Inc. Figure 40.21a Dandelions grow quickly and release a large number of tiny fruits.
  167. 167. © 2014 Pearson Education, Inc. Figure 40.21ba The Brazil nut tree produces a moderate number of large seeds in pods.
  168. 168. © 2014 Pearson Education, Inc. Figure 40.21bb The Brazil nut tree produces a moderate number of large seeds in pods.
  169. 169. © 2014 Pearson Education, Inc.  Other types of plants produce a moderate number of large seeds that provide a large store of energy that will help seedlings become established
  170. 170. © 2014 Pearson Education, Inc.  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
  171. 171. © 2014 Pearson Education, Inc. 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
  172. 172. © 2014 Pearson Education, Inc. Figure 40.22 When population density is low, b > m. As a result, the population grows until the density reaches Q. When population density is high, m > b, and the population shrinks until the density reaches Q. Equilibrium density (Q) Density-dependent birth rate (b) Density-independent death rate (m) Birthordeathrate percapita Population density
  173. 173. © 2014 Pearson Education, Inc. Mechanisms of Density-Dependent Population Regulation  Density-dependent birth and death rates are an example of negative feedback that regulates population growth  Density-dependent birth and death rates are affected by many factors, such as competition for resources, territoriality, disease, predation, toxic wastes, and intrinsic factors
  174. 174. © 2014 Pearson Education, Inc.  Competition for resources occurs in crowded populations; increasing population density intensifies competition for resources and results in a lower birth rate
  175. 175. © 2014 Pearson Education, Inc. Figure 40.23a Competition for resources
  176. 176. © 2014 Pearson Education, Inc.  Toxic wastes produced by a population can accumulate in the environment, contributing to density-dependent regulation of population size
  177. 177. © 2014 Pearson Education, Inc. Figure 40.23d Toxic wastes 5 µm
  178. 178. © 2014 Pearson Education, Inc.  Predation may increase with increasing population size due to predator preference for abundant prey species
  179. 179. © 2014 Pearson Education, Inc. Figure 40.23b Predation
  180. 180. © 2014 Pearson Education, Inc.  Territoriality can limit population density when space becomes a limited resource
  181. 181. © 2014 Pearson Education, Inc. Figure 40.23e Territoriality
  182. 182. © 2014 Pearson Education, Inc.  Disease transmission rates may increase with increasing population density
  183. 183. © 2014 Pearson Education, Inc. Figure 40.23c Disease
  184. 184. © 2014 Pearson Education, Inc.  Intrinsic factors (for example, physiological factors like hormonal changes) appear to regulate population size
  185. 185. © 2014 Pearson Education, Inc. Figure 40.23f Intrinsic factors
  186. 186. © 2014 Pearson Education, Inc. Population Dynamics  The study of population dynamics focuses on the complex interactions between biotic and abiotic factors that cause variation in population size
  187. 187. © 2014 Pearson Education, Inc. Stability and Fluctuation  Long-term population studies have challenged the hypothesis that populations of large mammals are relatively stable over time  Both weather and predator population can affect population size over time  For example, the moose population on Isle Royale collapsed during a harsh winter and when wolf numbers peaked
  188. 188. © 2014 Pearson Education, Inc. Figure 40.24 Numberofwolves Numberofmoose Year Wolves Moose 0 10 20 30 1,000 0 2,500 1,500 500 1955 1985 1995 20051965 1975 2,000 50 40
  189. 189. © 2014 Pearson Education, Inc. Immigration, Emigration, and Metapopulations  Metapopulations are groups of populations linked by immigration and emigration  Local populations within a metapopulation occupy patches of suitable habitat surrounded by unsuitable habitat  Populations can be replaced in patches after extinction or established in new unoccupied habitats through migration
  190. 190. © 2014 Pearson Education, Inc. Figure 40.25 Unoccupied patch EUROPE Aland Islands ° Occupied patch 5 km
  191. 191. © 2014 Pearson Education, Inc. Figure 40.25a
  192. 192. © 2014 Pearson Education, Inc. Figure 40.UN01a Number of generations Populationsize(N) = rmax N dt dN
  193. 193. © 2014 Pearson Education, Inc. Figure 40.UN01b = rmax N dt dN (K − N) K K = carrying capacity Number of generations Populationsize(N)
  194. 194. © 2014 Pearson Education, Inc. Figure 40.UN02
  195. 195. © 2014 Pearson Education, Inc. Figure 40.UN03 Meanheight(cm) Seed collection sites 1,000 0 3,000 100 50 2,000 Altitude(m) 0 Sierra Nevada Great Basin Plateau

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