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Chapter 50

Chapter 50. An Introduction to Ecology and the Biosphere. Overview: The Scope of Ecology Ecology Is the scientific study of the interactions between organisms and the environment These interactions Determine both the distribution of organisms and their abundance. Ecology

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Chapter 50

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  1. Chapter 50 An Introduction to Ecology and the Biosphere

  2. Overview: The Scope of Ecology • Ecology • Is the scientific study of the interactions between organisms and the environment • These interactions • Determine both the distribution of organisms and their abundance

  3. Ecology • Is an enormously complex and exciting area of biology • Reveals the richness of the biosphere Figure 50.1

  4. Concept 50.1: Ecology is the study of interactions between organisms and the environment • Ecology • Has a long history as a descriptive science • Is also a rigorous experimental science

  5. Ecology and Evolutionary Biology • Events that occur in ecological time • Affect life on the scale of evolutionary time

  6. Organisms and the Environment • The environment of any organism includes • Abiotic, or nonliving components • Biotic, or living components • All the organisms living in the environment, the biota

  7. Climate in northern Australia is hot and wet, with seasonal drought. Kangaroos/km2 > 20 10–20 5–10 1–5 0.1–1 Red kangaroos occur in most semiarid and arid regions of the interior, where precipitation is relatively low and variable from year to year. < 0.1 Limits ofdistribution Southeastern Australia has a wet, cool climate. Southern Australia has cool, moist winters and warm, dry summers. Tasmania • Environmental components • Affect the distribution and abundance of organisms Figure 50.2

  8. Ecologists • Use observations and experiments to test explanations for the distribution and abundance of species

  9. (a) Organismal ecology. How do humpback whales select their calving areas? Subfields of Ecology • Organismal ecology • Studies how an organism’s structure, physiology, and (for animals) behavior meet the challenges posed by the environment Figure 50.3a

  10. Population ecology. What environmental factors affect the reproductive rate of deer mice? (b) • Population ecology • Concentrates mainly on factors that affect how many individuals of a particular species live in an area Figure 50.3b

  11. Community ecology • Deals with the whole array of interacting species in a community (c) Community ecology.What factors influencethe diversity of speciesthat make up aparticular forest? Figure 50.3c

  12. Ecosystem ecology • Emphasizes energy flow and chemical cycling among the various biotic and abiotic components (d) Ecosystem ecology. Whatfactors control photosyntheticproductivity in a temperategrassland ecosystem? Figure 50.3d

  13. (e) Landscape ecology. To what extent do the trees lining the drainage channels in this landscape serve as corridors of dispersal for forest animals? • Landscape ecology • Deals with arrays of ecosystems and how they are arranged in a geographic region Figure 50.3e

  14. The biosphere • Is the global ecosystem, the sum of all the planet’s ecosystems

  15. Most ecologists follow the precautionary principle regarding environmental issues • The precautionary principle • Basically states that humans need to be concerned with how their actions affect the environment

  16. Concept 50.2: 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

  17. Palearctic Nearctic Tropic of Cancer (23.5N) Oriental Ethiopian Equator Neotropical (23.5S) Tropic of Capricorn Australian • Many naturalists • Began to identify broad patterns of distribution by naming biogeographic realms Figure 50.5

  18. Species absent because Area inaccessible or insufficient time Yes Yes Dispersallimitsdistribution? Habitat selection Yes Predation, parasitism,competition, disease Chemical factors Behaviorlimitsdistribution? Biotic factors(other species)limitdistribution? No WaterOxygen Salinity pHSoil nutrients, etc. No Abiotic factorslimitdistribution? No TemperatureLight Soil structure FireMoisture, etc. Physical factors • Biogeography • Provides a good starting point for understanding what limits the geographic distribution of species Figure 50.6

  19. Dispersal and Distribution • Dispersal • Is the movement of individuals away from centers of high population density or from their area of origin • Contributes to the global distribution of organisms

  20. New areasoccupied Year 1996 1989 1974 Natural Range Expansions • Natural range expansions • Show the influence of dispersal on distribution Figure 50.7

  21. Species Transplants • Species transplants • Include organisms that are intentionally or accidentally relocated from their original distribution • Can often disrupt the communities or ecosystems to which they have been introduced

  22. Behavior and Habitat Selection • Some organisms • Do not occupy all of their potential range • Species distribution • May be limited by habitat selection behavior

  23. Biotic Factors • Biotic factors that affect the distribution of organisms may include • Interactions with other species • Predation • Competition

  24. W. J. Fletcher tested the effects of two algae-eating animals, sea urchins and limpets, on seaweed abundance near Sydney, Australia. In areas adjacent to a control site, either the urchins, the limpets, or both were removed. EXPERIMENT Fletcher observed a large difference in seaweed growth between areas with and without sea urchins. RESULTS Removing bothlimpets andurchins orremoving onlyurchins increasedseaweed coverdramatically. 100 Seaurchin Both limpetsand urchinsremoved 80 Onlyurchinsremoved 60 Seaweed cover (%) Limpet 40 Almost noseaweed grew in areas whereboth urchins andlimpets werepresent, or whereonly limpets wereremoved. Only limpets removed Control (bothurchins andlimpets present) 20 0 February 1984 February 1983 August 1983 August 1982 Removing both limpets and urchins resulted in the greatest increase of seaweed cover, indicating that bothspecies have some influence on seaweed distribution. But since removing only urchins greatly increased seaweed growth whileremoving only limpets had little effect, Fletcher concluded that sea urchins have a much greater effect than limpets in limitingseaweed distribution. CONCLUSION • A specific case of an herbivore limiting distribution of a food species Figure 50.8

  25. Abiotic Factors • Abiotic factors that affect the distribution of organisms may include • Temperature • Water • Sunlight • Wind • Rocks and soil

  26. Temperature • Environmental temperature • Is an important factor in the distribution of organisms because of its effects on biological processes

  27. Water • Water availability among habitats • Is another important factor in species distribution

  28. Sunlight • Light intensity and quality • Can affect photosynthesis in ecosystems • Light • Is also important to the development and behavior of organisms sensitive to the photoperiod

  29. Wind • Wind • Amplifies the effects of temperature on organisms by increasing heat loss due to evaporation and convection • Can change the morphology of plants Figure 50.9

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

  31. Climate • Four major abiotic components make up climate • Temperature, water, sunlight, and wind • Climate • Is the prevailing weather conditions in a particular area

  32. Climate patterns can be described on two scales • Macroclimate, patterns on the global, regional, and local level • Microclimate, very fine patterns, such as those encountered by the community of organisms underneath a fallen log

  33. Global Climate Patterns • Earth’s global climate patterns • Are determined largely by the input of solar energy and the planet’s movement in space

  34. LALITUDINAL VARIATION IN SUNLIGHT INTENSITY North Pole60N Low angle of incoming sunlight 30N Tropic ofCancer Sunlight directly overhead 0 (equator) Tropic ofCapricorn 30S Low angle of incoming sunlight 60S South pole Figure 50.10 Atmosphere • Sunlight intensity • Plays a major part in determining the Earth’s climate patterns

  35. SEASONAL VARIATION IN SUNLIGHT INTENSITY March equinox: Equator faces sun directly; neither pole tilts toward sun; all regions on Earth experience 12 hours of daylight and 12 hours of darkness. 60N June solstice: Northern Hemisphere tilts toward sun; summer begins in Northern Hemisphere; winter begins in Southern Hemisphere. 30N 0 (equator) 30S December solstice: Northern Hemisphere tilts away from sun; winter begins in Northern Hemisphere; summer begins in Southern Hemisphere. Constant tilt of 23.5 September equinox: Equator faces sun directly; neither pole tilts toward sun; all regions on Earth experience 12 hours of daylight and 12 hours of darkness. Figure 50.10

  36. GLOBAL AIR CIRCULATION AND PRECIPITATION PATTERNS 60N 30N Descending dry air absorbs moisture Descending dry air absorbs moisture 0 (equator) Ascending moist air releases moisture 30S 0 23.5 60S 23.5 30 30 Aridzone Aridzone Tropics • Air circulation and wind patterns • Play major parts in determining the Earth’s climate patterns Figure 50.10

  37. GLOBAL WIND PATTERNS ArcticCircle 60N Westerlies 30N Northeast trades Doldrums 0 (equator) Southeast trades 30S Westerlies 60S AntarcticCircle Figure 50.10

  38. Regional, Local, and Seasonal Effects on Climate • Various features of the landscape • Contribute to local variations in climate

  39. Warm air over land rises. 1 Cooler air sinks over water. 3 Air cools at high elevation. 2 Cool air over water moves inland, replacing rising warm air over land. 4 Bodies of Water • Oceans and their currents, and large lakes • Moderate the climate of nearby terrestrial environments Figure 50.11

  40. As moist air moves in off the Pacific Ocean and encounters the westernmost mountains, it flows upward, cools at higher altitudes, and drops a large amount of water. The world’s tallest trees, the coastal redwoods, thrive here. 1 Farther inland, precipitation increases again as the air moves up and over higher mountains. Some of the world’s deepest snow packs occur here. 2 On the eastern side of the Sierra Nevada, there is little precipitation. As a result of this rain shadow, much of central Nevada is desert. 3 Wind direction East PacificOcean Sierra Nevada CoastRange Figure 50.12 Mountains • Mountains have a significant effect on • The amount of sunlight reaching an area • Local temperature • Rainfall

  41. Seasonality • The angle of the sun • Leads to many seasonal changes in local environments

  42. In autumn, as surface water cools rapidly, it sinks below the underlying layers, remixing the water until the surface begins to freeze and the winter temperature profile is reestablished. In winter, the coldest water in the lake (0°C) lies just below the surface ice; water is progressively warmer at deeper levels of the lake, typically 4–5°C at the bottom. In summer, the lake regains a distinctive thermal profile, with warm surface water separated from cold bottom water by a narrow vertical zone of rapid temperature change, called a thermocline. 1 4 3 8 8 In spring, as the sun melts the ice, the surface water warms to 4°C and sinks below the cooler layers immediately below, eliminating the thermal stratification. Spring winds mix the water to great depth, bringing oxygen (O2) to the bottom waters (see graphs) and nutrients to the surface. 2 16 16 24 24 Spring O2 (mg/L) Winter O2 (mg/L) 0 4 8 12 0 8 12 4 Lake depth (m) Lake depth (m) 8 16 24 O2 concentration High Medium Low 4 0 O2 (mg/L) 4 2 O2 (mg/L) 4 4 8 0 4 12 0 4 8 12 4 4 Lake depth (m) Lake depth (m) 4 4 22 4 8 20 4 4C 4C 4 18 4 16 8 6 4 5 4C 24 4C Autumn Thermocline Summer • Lakes • Are sensitive to seasonal temperature change • Experience seasonal turnover Figure 50.13

  43. Microclimate • Microclimate • Is determined by fine-scale differences in abiotic factors

  44. Current range Predictedrange Overlap (a) 4.5C warming overnext century (b) 6.5C warming overnext century Long-Term Climate Change • One way to predict future global climate change • Is to look back at the changes that occurred previously Figure 50.14

  45. Concept 50.3: Abiotic and biotic factors influence the structure and dynamics of aquatic biomes • Varying combinations of both biotic and abiotic factors • Determine the nature of Earth’s many biomes • Biomes • Are the major types of ecological associations that occupy broad geographic regions of land or water

  46. 30N Tropic of Cancer Equator Continentalshelf Tropic of Capricorn 30S Key Rivers Abyssal zone(below oceanicpelagic zone) Lakes Estuaries Intertidal zone Coral reefs Oceanic pelagiczone • The examination of biomes will begin with Earth’s aquatic biomes Figure 50.15

  47. Aquatic biomes • Account for the largest part of the biosphere in terms of area • Can contain fresh or salt water • Oceans • Cover about 75% of Earth’s surface • Have an enormous impact on the biosphere

  48. Intertidal zone Neritic zone Oceanic zone Littoralzone Limneticzone 0 Photic zone 200 m Continentalshelf Pelagic zone Benthiczone Aphoticzone Photiczone Pelagiczone Benthiczone Aphoticzone (a) Zonation in a lake. The lake environment is generally classified on the basis of three physical criteria: light penetration (photic and aphotic zones), distance from shore and water depth (littoral and limnetic zones), and whether it is open water (pelagic zone) or bottom (benthic zone). 2,500–6,000 m Abyssal zone(deepest regions of ocean floor) (b) Marine zonation. Like lakes, the marine environment is generally classified on the basis of light penetration (photic and aphotic zones), distance from shore and water depth (intertidal, neritic, and oceanic zones), and whether it is open water (pelagic zone) or bottom (benthic and abyssal zones). • Many aquatic biomes • Are stratified into zones or layers defined by light penetration, temperature, and depth Figure 50.16a, b

  49. LAKES An oligotrophic lake in Grand Teton, Wyoming A eutrophic lake in Okavango delta, Botswana • Lakes Figure 50.17

  50. WETLANDS Figure 50.17 Okefenokee National Wetland Reserve in Georgia • Wetlands

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