1. The Biosphere and Human Effects Chapter 18

2. 18.3 Types of Land Ecosystems • Different climates support different types of plant life, which support different types of animals • Biome • Type of ecosystem that can be characterized by its climate and dominant vegetation

3. Deserts • Low rainfall produces deserts at latitudes around 30° north and south, where dry air descends • Desert • Biome where little rain falls, humidity is low, and the main plants store water in their tissues or tap into water sources deep underground

4. Desert

5. Grasslands • Grasslands form at midlatitudes in the interior of continents between deserts and temperate forests • Grasslands • Biome where grasses and other low-growing plants are adapted to warm summers, cold winters, periodic fires, and grazing animals • Example: shortgrass and tallgrass prairies

6. Chaparral • Dry shrublands (chaparral) are found in South Africa, California, and Mediterranean regions • Chaparral • Biome where cool, wet winters and hot, dry summers support shrubs adapted to periodic fires

7. Grasslands and Chaparral

8. Grassland, shrublands, and woodlands Fig. 18-5c, p. 365

9. Tropical Rain Forests • At the equator, high rainfall and temperature support tropical rain forests with broadleaf trees that remain green year-round • Tropical rain forest • Species-rich tropical biome in which continual warmth and rainfall allows dominant broadleaf trees to grow all year

10. Tropical Rain Forest

11. Deciduous Broadleaf Forests • Deciduous broadleaf trees are adapted to regions that cannot sustain year-round growth • Deciduous tree • A tree that drops all its leaves annually just before a season that does not favor growth • Temperate deciduous forest • Biome dominated by trees that drop all their leaves and go dormant during a cold winter

12. Deciduous Broadleaf Forest

13. Coniferous Forests • Conifer forests dominate high latitudes in the Northern Hemisphere and other regions where drought, poor soil, or periodic fires prevent broadleaf trees from taking hold • Taiga (boreal forest) • Extensive northern biome dominated by conifers • A cold, dry season alternates with a cool, rainy season

14. Coniferous Forest: Siberian Taiga

15. Tundra • Tundra forms at high latitudes and high altitudes • Arctic tundra • Youngest, most northerly biome, dominated by low plants adapted to a short growing season and a layer of permanently frozen soil (permafrost) • Alpine tundra • High-altitude biome dominated by low plants

16. Arctic Tundra

17. Animation: Major biomes

18. Animation: Environmental gradient

19. 18.4 Types of Aquatic Ecosystems • Composition of aquatic communities is influenced by gradients of sunlight penetration, water temperature, salinity, dissolved gases, rate of water movement, and depth

20. Freshwater Ecosystems • A lake is a standing body of water • Light decreases with depth; different communities live at different depths and distances from shore • Streams and rivers are flowing water ecosystems • Physical characteristics that vary along its length influence the types of organisms that live in it • Fast-flowing cooler water holds more oxygen than warmer, slower-moving water

21. Marine Ecosystems • Estuary • A semi-enclosed area where nutrient-rich water from a river mixes with seawater • Highly productive ecosystem • Seashores • Rocky shores have grazing food chains based on algae; sandy shores have detrital food chains

22. Marine Ecosystems • Benthic province • The ocean’s rocks and sediments • Pelagic province • The ocean’s open waters • In upper waters, photosynthetic organisms form the basis of grazing food chains • Deeper communities subsist on materials that drift down from above

23. Marine Ecosystems • Coral reefs • Formation composed of secretions of coral polyps, found in tropical, sunlit seas • Main producers are photosynthetic protists that live inside the coral’s tissues • Coral bleaching • Stress response in which a coral expels the photosynthetic protists in its issues

24. Coral Reef and Bleaching

25. water of the open ocean water over continental shelf air at ocean surface continental shelf sunlit water Pelagic Province 0 “twilight” water 200 sunless water 1,000 2,000 Benthic Province 4,000 deep-sea trenches 11,000 depth (meters) Fig. 18-10a, p. 369

26. Animation: Oceanic zones

27. Marine Ecosystems • Seamount • An undersea mountain • Hydrothermal vent • Place where hot, mineral-rich water streams out from an underwater opening in the Earth’s crust • Producers are prokaryotes that strip energy from minerals

28. Seamounts and Hydrothermal Vents

29. Comparing Aquatic Ecosystems • In well-lit upper waters, photosynthetic producers are the base for grazing food chains • Detritus drifting down from above sustains most deep-water communities in lakes and oceans • Hydrothermal vent communities on the ocean floor are sustained by energy that prokaryotes harvest from minerals

30. Animation: Lake zonation

31. Animation: Lake turnover

32. Animation: Rocky intertidal zones

33. Animation: Three types of reefs

34. Animation: Hydrothermal vent community

35. Animation: Coastal upwelling

36. 18.5 Human Effects on the Biosphere • The increasing size of the human population and its increasing industrialization have far-reaching effects on the biosphere • Effects range from extinction of individual species to global climate change

37. Increasing Species Extinctions • Humans are increasing the rate of species extinctions by degrading, destroying, and fragmenting natural habitats, by overharvesting species, and by introducing exotic species

38. Increasing Species Extinctions • Endangered species • Faces extinction in all or part of its range • Threatened species • Likely to become endangered in the near future • Endemic species • Evolved in one place and is found nowhere else

39. Living or Extinct? • Ivory-billed woodpecker

40. Threatened Species • Habitat destruction threatens the eastern prairie fringed orchid – aquifer depletion and pollution endanger Texas blind salamanders

41. Some Threatened Species

42. The Global Impact of Human Activities • Human activities threaten entire ecosystems • Desertification • Deforestation • Air pollution and acid rain • Water pollution • Trash in aquatic ecosystems • Air pollution and the ozone hole • Greenhouse gases and global warming

43. Desertification • Poor agricultural practices turn grasslands or woodlands into deserts • US Great Plains (the Great Dustbowl) • Sahara Desert • Desertification • Conversion of grassland or woodlands to desertlike conditions

44. Desertification • Dust from the Sahara over the Atlantic Ocean

45. Deforestation • Human activities strip woodlands of trees • Flooding • Landslides • Increases atmospheric CO2 • Decreases atmospheric oxygen • Deforestation • Removal of all trees from a large tract of land

46. Deforestation • Clearing tropical forests in Brazil

47. Pollution • Human activities generate pollutants that kill animals and damage ecosystems • Pollutant • Natural or man-made substance released into the environment in greater than natural amounts, and that damages the health of organisms

48. Acid Rain • Acid rain • Rainfall contaminated by acidic pollutants • Burns trees, kills fish, leaches nutrients from soil • Caused by pollutants that combine with water vapor in the atmosphere to form acids • Sulfuric acid from sulfur dioxides from coal-burning power plants and factories • Nitric acid from nitrogen oxides from vehicles and power plants that burn gas and oil

49. Acid Rain

50. Other Sources of Water Pollution • Pollution from point sources may be identified; dealing with pollution from nonpoint sources is more difficult • Industrial chemicals and heavy metals • Oil from vehicles • Runoff of fertilizers, pesticides, herbicides, and animal wastes • Sewage and excreted prescription drugs • Sediments