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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 distribution of organisms and their abundance

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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 distribution of organisms and their abundance • Ecology reveals the richness of the biosphere

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

  4. Organisms and the Environment • The environment of any organism includes: • Abiotic, or nonliving, components • Biotic, or living, components • All the organisms that are part of the individual’s environment are collectively called the biota • Environmental components affect the distribution and abundance of organisms

  5. LE 50-2 Kangaroos/km2 > 20 10–20 5–10 1–5 0.1–1 < 0.1 Limits of distribution Tasmania

  6. Ecologists use observations and experiments to test explanations for the distribution and abundance of species • Organismal ecology studies how an organism’s structure, physiology, and (for animals) behavior meet environmental challenges

  7. LE 50-3a Organismal ecology

  8. Population ecology focuses on factors affecting how many individuals of a species live in an area Population ecology

  9. Community ecology deals with the whole array of interacting species in a community Community ecology

  10. Ecosystem ecology emphasizes energy flow and chemical cycling among the various biotic and abiotic components Ecosystem ecology

  11. Landscape ecology deals with arrays of ecosystems and how they are arranged in a geographic region Landscape ecology

  12. The biosphere is the global ecosystem, the sum of all the planet’s ecosystems • Ecology provides the scientific understanding underlying environmental issues • Rachel Carson is credited with starting the modern environmental movement

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

  14. 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 • Many naturalists began to identify broad patterns of distribution by naming biogeographic realms • Biogeography is a good starting point for understanding what limits geographic distribution of species

  15. LE 50-5 Palearctic Nearctic Tropic of Cancer (23.5°N) Oriental Ethiopian Equator Neotropical (23.5°S) Tropic of Capricorn Australian

  16. LE 50-6 Species absent because Area inaccessible or insufficient time Yes Yes Dispersal limits distribution? Habitat selection Yes Predation, parasitism, competition, disease Chemical factors Behavior limits distribution? No Biotic factors (other species) limit distribution? Water Oxygen Salinity pH Soil nutrients, etc. No Abiotic factors limit distribution? No Temperature Light Soil structure Fire Moisture, etc. Physical factors

  17. 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 • Natural range expansions show the influence of dispersal on distribution

  18. LE 50-7 New areas occupied Year 1996 1989 1974

  19. Species Transplants • Species transplants include organisms that are intentionally or accidentally relocated from their original distribution • Species transplants can disrupt the communities or ecosystems to which they have been introduced • Some organisms do not occupy all of their potential range • Species distribution may be limited by habitat selection behavior

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

  21. LE 50-8 100 Sea urchin Both limpets and urchins removed 80 Only urchins removed 60 Seaweed cover (%) Limpet 40 Only limpets removed Control (both urchins and limpets present) 20 0 August 1982 February 1984 August 1983 February 1983

  22. Abiotic Factors • Abiotic factors affecting distribution of organisms: • Temperature • Water • Sunlight • Wind • Rocks and soil

  23. Factors to Distribution • Environmental temperature is an important factor in distribution of organisms because of its effects on biological processes • Water availability in habitats is another important factor in species distribution • Light intensity and quality affects photosynthesis • Light is also important to development and behavior of organisms sensitive to photoperiod • Wind amplifies effects of temperature by increasing heat loss from evaporation and convection • Wind can change morphology of plants

  24. Factors to Distribution • Many characteristics of soil (Rocks and Soil )limit distribution of plants and thus the animals that feed upon them: • Physical structure • pH • Mineral composition

  25. Climate • Four major abiotic components of climate: temperature, water, sunlight, and wind • Climate is the prevailing weather in an area • 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

  26. 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

  27. LE 50-10a North Pole 60°N Low angle of incoming sunlight 30°N Tropic of Cancer Sunlight directly overhead at equinoxes 0° (equator) Tropic of Capricorn 30°S Low angle of incoming sunlight 60°S South Pole Atmosphere

  28. Seasonal variations of light and temperature increase steadily toward the poles

  29. LE 50-10b 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 30°N June solstice: Northern Hemisphere tilts toward sun; summer begins in Northern Hemisphere; winter begins in Southern Hemisphere. 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.

  30. Global air circulation and wind patterns play major roles in determining climate patterns

  31. LE 50-10c 60°N 30°N Descending dry air absorbs moisture Descending dry air absorbs moisture 0° (equator) Ascending moist air releases moisture 30°S 60°S 0° 23.5° 23.5° 30° 30° Arid zone Arid zone Tropics

  32. LE 50-10d Arctic Circle 60°N Westerlies 30°N Northeast trades Doldrums 0° (equator) Southeast trades 30°S Westerlies 60°S Antarctic Circle

  33. Regional, Local, and Seasonal Effects on Climate • Various features of the landscape contribute to local variations in climate • Seasonal variation also influences climate • Oceans and their currents and large lakes moderate the climate of nearby terrestrial environments

  34. Mountains • Mountains have a significant effect on • The amount of sunlight reaching an area • Local temperature • Rainfall

  35. LE 50-12 Wind direction East Pacific Ocean Sierra Nevada Coast Range

  36. Seasonality • The angle of the sun leads to many seasonal changes in local environments • Lakes are sensitive to seasonal temperature change and experience seasonal turnover

  37. LE 50-13 Spring Winter O2 (mg/L) O2 (mg/L) 0 4 8 12 0 4 8 12 Lake depth (m) Lake depth (m) 8 8 16 16 0° 4° 4° 2° 24 24 4° 4° 4° 4° 4° 4° 4°C 4°C O2 concentration High (>8 mg/L) Medium (4–8 mg/L) Low (<4 mg/L) O2 (mg/L) O2 (mg/L) 0 4 8 12 0 4 8 12 Lake depth (m) Lake depth (m) 4° 22° 8 8 4° 20° 18° 4° 8° 4° 16 16 6° 4° 5° 4°C 4°C 24 24 Summer Thermocline Autumn

  38. Microclimate • Microclimate is determined by fine-scale differences in abiotic factors Long-Term Climate Change: • One way to predict future global climate change is to study previous changes

  39. LE 50-14 Current range Predicted range Overlap 4.5°C warming over next century 6.5°C warming over next century

  40. Concept 50.3: Abiotic and biotic factors influence the structure and dynamics of aquatic biomes • Varying combinations of biotic and abiotic factors determine the nature of biomes • Biomes are the major ecological associations that occupy broad geographic regions of land or water • Aquatic biomes account for the largest part of the biosphere in terms of area • They can contain fresh water or salt water • Oceans cover about 75% of Earth’s surface and have an enormous impact on the biosphere

  41. LE 50-15 30°N Tropic of Cancer Equator Continental shelf Tropic of Capricorn 30°S Key Lakes Abyssal zone (below oceanic pelagic zone) Estuaries Rivers Oceanic pelagic zone Intertidal zone Coral reefs

  42. Many aquatic biomes are stratified into zones or layers defined by light penetration, temperature, and depth

  43. LE 50-16a Littoral zone Limnetic zone Photic zone Pelagic zone Benthic zone Aphotic zone Zonation in a lake

  44. LE 50-16b Intertidal zone Neritic zone Oceanic zone 0 Photic zone 200 m Continental shelf Pelagic zone Benthic zone Aphotic zone 2,500–6,000 m Abyssal zone (deepest regions of ocean floor) Marine zonation

  45. Major aquatic biomes: • Lakes • Wetlands • Streams and rivers • Estuaries • Intertidal zones • Oceanic pelagic biome • Coral reefs • Marine benthic zone

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