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

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

  5. 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

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

  7. Ecologists use observations and experiments to test explanations for the distribution and abundance of species

  8. Subfields of Ecology • Organismal ecology studies how an organism’s structure, physiology, and (for animals) behavior meet environmental challenges

  9. LE 50-3a Organismal ecology

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

  11. LE 50-3b Population ecology

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

  13. LE 50-3c Community ecology

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

  15. LE 50-3d Ecosystem ecology

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

  17. LE 50-3e Landscape ecology

  18. The biosphere is the global ecosystem, the sum of all the planet’s ecosystems

  19. Ecology and Environmental Issues • Ecology provides the scientific understanding underlying environmental issues • Rachel Carson is credited with starting the modern environmental movement

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

  21. 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

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

  23. Biogeography is a good starting point for understanding what limits geographic distribution of species

  24. 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

  25. 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

  26. Natural Range Expansions • Natural range expansions show the influence of dispersal on distribution

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

  28. 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

  29. Behavior and Habitat Selection • Some organisms do not occupy all of their potential range • Species distribution may be limited by habitat selection behavior

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

  31. 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

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

  33. Temperature • Environmental temperature is an important factor in distribution of organisms because of its effects on biological processes

  34. Water • Water availability in habitats is another important factor in species distribution

  35. Sunlight • Light intensity and quality affects photosynthesis • Light is also important to development and behavior of organisms sensitive to photoperiod

  36. Wind • Wind amplifies effects of temperature by increasing heat loss from evaporation and convection • Wind can change morphology of plants

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

  38. 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

  39. Global Climate Patterns • Global climate patterns are determined largely by solar energy and the planet’s movement in space

  40. Sunlight intensity plays a major part in determining the Earth’s climate patterns

  41. 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

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

  43. 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.

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

  45. 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

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

  47. Regional, Local, and Seasonal Effects on Climate • Various features of the landscape contribute to local variations in climate • Seasonal variation also influences climate

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