Population Ecology and the Distribution of Organisms

1. Population Ecology and the Distribution of Organisms 0 40

2. 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. 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. Figure 40.1

5. Figure 40.2 Global ecology Landscape ecology Ecosystem ecology Community ecology Population ecology Organismal ecology

6. 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. Figure 40.2a Global ecology

8. 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. Figure 40.2b Landscape ecology

10. 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. Figure 40.2c Ecosystem ecology

12. 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. Figure 40.2d Community ecology

14. 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. Figure 40.2e Population ecology

16. 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. Figure 40.2f Organismal ecology

18. 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. 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. 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. 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. Figure 40.3a Atmosphere 90N (North Pole) Low angle of incoming sunlight 23.5N (Tropic of Cancer) Sun overhead at equinoxes 0 (Equator) 23.5S (Tropic of Capricorn) Low angle of incoming sunlight 90S (South Pole) Latitudinal variation in sunlight intensity

23. 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. Figure 40.3b 66.5N (Arctic Circle) Descending dry air absorbs moisture. 30N 60N Westerlies 30N Ascending moist air releases moisture. Northeast trades 0 Southeast trades 0 30S Westerlies 60S 66.5S (Antarctic Circle) Global air circulation and precipitation patterns

25. 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. Figure 40.3ba 66.5N (Arctic Circle) 60N Westerlies 30N Northeast trades 0 Southeast trades 30S Westerlies 60S 66.5S (Antarctic Circle) Global air circulation and precipitation patterns

27. Figure 40.3bb Descending dry air absorbs moisture. 30N Ascending moist air releases moisture. 0 Global air circulation and precipitation patterns

28. Regional Effects on Climate Climate is affected by seasonality, large bodies of water, and mountains

29. 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. Figure 40.4 March equinox December solstice 60N Constant tilt of 23.5 30N June solstice 0 (equator) 30S September equinox

31. 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. Figure 40.5 Labrador Current California Current Gulf Stream ATLANTIC OCEAN PACIFIC OCEAN

33. 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. Figure 40.6 Leeward side of mountains Air flow Mountain range Ocean

35. 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. 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. 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. Figure 40.7 30N Tropic of Cancer Equator Tropic of Capricorn 30S Temperate broadleaf forest Tropical forest Northern coniferous forest Savanna Tundra Desert High mountains Chaparral Polar ice Temperate grassland

39. 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. Figure 40.8 Temperate grassland Desert Tropical forest 30 Temperate broadleaf forest 15 Annual mean temperature (C) Northern coniferous forest 0 Arctic and alpine tundra 15 0 200 100 400 300 Annual mean precipitation (cm)

41. 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. 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. 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. Terrestrial biomes can be characterized by distribution, precipitation, temperature, plants, and animals

45. 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. Figure 40.9a A tropical rain forest in Costa Rica

47. 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. Savannaoccurs in equatorial and subequatorial regions Precipitation is seasonal Temperature averages 24–29C but is more seasonally variable than in the tropics

49. Figure 40.9b A savanna in Kenya

50. 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