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Chapter 3

Chapter 3. Ecosystems: What Are They and How Do They Work?. Have You Thanked the Insects Today?. Many plant species depend on insects for pollination. Insects can control other pest insects by eating them. Figure 3-1. Have You Thanked the Insects Today?.

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Chapter 3

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  1. Chapter 3 Ecosystems: What Are They and How Do They Work?

  2. Have You Thanked the Insects Today? • Many plant species depend on insects for pollination. • Insects can control other pest insects by eating them Figure 3-1

  3. Have You Thanked the Insects Today? • …if all insects disappeared, humanity probably could not last more than a few months [E.O. Wilson, Biodiversity expert]. • Insect’s role in nature is part of the larger biological community in which they live.

  4. THE NATURE OF ECOLOGY • Ecology is a study of connections in nature. • How organisms interact with one another and with their nonliving environment. Figure 3-2

  5. Organisms and Species • Organisms, the different forms of life on earth, can be classified into different species based on certain characteristics. Figure 3-3

  6. Which Species Run the World? • Multitudes of tiny microbes such as bacteria, protozoa, fungi, and yeast help keep us alive. • Harmful microbes are the minority. • Soil bacteria convert nitrogen gas to a usable form for plants. • They help produce foods (bread, cheese, yogurt, beer, wine). • 90% of all living mass. • Helps purify water, provide oxygen, breakdown waste. • Lives beneficially in your body (intestines, nose).

  7. Populations, Communities, and Ecosystems • Members of a species interact in groups called populations. • Populations of different species living and interacting in an area form a community. • A community interacting with its physical environment of matter and energy is an ecosystem.

  8. Populations • A population is a group of interacting individuals of the same species occupying a specific area. • The space an individual or population normally occupies is its habitat. Figure 3-4

  9. Populations • Genetic diversity • In most natural populations individuals vary slightly in their genetic makeup. Figure 3-5

  10. THE EARTH’S LIFE SUPPORT SYSTEMS • The biosphere consists of several physical layers that contain: • Air • Water • Soil • Minerals • Life Figure 3-6

  11. Biosphere • Atmosphere • Membrane of air around the planet. • Stratosphere • Lower portion contains ozone to filter out most of the sun’s harmful UV radiation. • Hydrosphere • All the earth’s water: liquid, ice, water vapor • Lithosphere • The earth’s crust and upper mantle.

  12. What Sustains Life on Earth? • Solar energy, the cycling of matter, and gravity sustain the earth’s life. Figure 3-7

  13. What Happens to Solar Energy Reaching the Earth? • Solar energy flowing through the biosphere warms the atmosphere, evaporates and recycles water, generates winds and supports plant growth. Figure 3-8

  14. ECOSYSTEM COMPONENTS • Life exists on land systems called biomes and in freshwater and ocean aquatic life zones. Figure 3-9

  15. Average annual precipitation 100–125 cm (40–50 in.) 75–100 cm (30–40 in.) 50–75 cm (20–30 in.) 4,600 m (15,000 ft.) 25–50 cm (10–20 in.) 3,000 m (10,000 ft.) below 25 cm (0–10 in.) 1,500 m (5,000 ft.) Coastal mountain ranges Sierra Nevada Mountains Great American Desert Rocky Mountains Great Plains Mississippi River Valley Appalachian Mountains Coastal chaparral and scrub Coniferous forest Prairie grassland Coniferous forest Desert Deciduous forest Fig. 3-9, p. 56

  16. Nonliving and Living Components of Ecosystems • Ecosystems consist of nonliving (abiotic) and living (biotic) components. Figure 3-10

  17. Factors That Limit Population Growth • Availability of matter and energy resources can limit the number of organisms in a population. Figure 3-11

  18. Factors That Limit Population Growth • The physical conditions of the environment can limit the distribution of a species. Figure 3-12

  19. Producers: Basic Source of All Food • Most producers capture sunlight to produce carbohydrates by photosynthesis:

  20. Producers: Basic Source of All Food • Chemosynthesis: • Some organisms such as deep ocean bacteria draw energy from hydrothermal vents and produce carbohydrates from hydrogen sulfide (H2S) gas .

  21. Photosynthesis: A Closer Look • Chlorophyll molecules in the chloroplasts of plant cells absorb solar energy. • This initiates a complex series of chemical reactions in which carbon dioxide and water are converted to sugars and oxygen. Figure 3-A

  22. Consumers: Eating and Recycling to Survive • Consumers (heterotrophs) get their food by eating or breaking down all or parts of other organisms or their remains. • Herbivores • Primary consumers that eat producers • Carnivores • Primary consumers eat primary consumers • Third and higher level consumers: carnivores that eat carnivores. • Omnivores • Feed on both plant and animals.

  23. Decomposers and Detrivores • Decomposers: Recycle nutrients in ecosystems. • Detrivores: Insects or other scavengers that feed on wastes or dead bodies. Figure 3-13

  24. Aerobic and Anaerobic Respiration: Getting Energy for Survival • Organisms break down carbohydrates and other organic compounds in their cells to obtain the energy they need. • This is usually done through aerobic respiration. • The opposite of photosynthesis

  25. Aerobic and Anaerobic Respiration: Getting Energy for Survival • Anaerobic respiration or fermentation: • Some decomposers get energy by breaking down glucose (or other organic compounds) in the absence of oxygen. • The end products vary based on the chemical reaction: • Methane gas • Ethyl alcohol • Acetic acid • Hydrogen sulfide

  26. Two Secrets of Survival: Energy Flow and Matter Recycle • An ecosystem survives by a combination of energy flow and matter recycling. Figure 3-14

  27. BIODIVERSITY Figure 3-15

  28. Biodiversity Loss and Species Extinction: Remember HIPPO • H for habitat destruction and degradation • I for invasive species • P for pollution • P for human population growth • O for overexploitation

  29. Why Should We Care About Biodiversity? • Biodiversity provides us with: • Natural Resources (food water, wood, energy, and medicines) • Natural Services (air and water purification, soil fertility, waste disposal, pest control) • Aesthetic pleasure

  30. Solutions • Goals, strategies and tactics for protecting biodiversity. Figure 3-16

  31. ENERGY FLOW IN ECOSYSTEMS • Food chains and webs show how eaters, the eaten, and the decomposed are connected to one another in an ecosystem. Figure 3-17

  32. Food Webs • Trophic levels are interconnected within a more complicated food web. Figure 3-18

  33. Energy Flow in an Ecosystem: Losing Energy in Food Chains and Webs • In accordance with the 2nd law of thermodynamics, there is a decrease in the amount of energy available to each succeeding organism in a food chain or web.

  34. Energy Flow in an Ecosystem: Losing Energy in Food Chains and Webs • Ecological efficiency: percentage of useable energy transferred as biomass from one trophic level to the next. Figure 3-19

  35. Productivity of Producers: The Rate Is Crucial • Gross primary production (GPP) • Rate at which an ecosystem’s producers convert solar energy into chemical energy as biomass. Figure 3-20

  36. Net Primary Production (NPP) • NPP = GPP – R • Rate at which producers use photosynthesis to store energy minus the rate at which they use some of this energy through respiration (R). Figure 3-21

  37. Trophic Levels • 1st Level: Autotrophs/producers “self-feeders” • 2nd Level: Herbivores/heterotrophs/primary consumers “other feeders” • Eat autotrophs • Often a prey species

  38. Trophic Levels • 3rd Level: Heterotrophs/secondary consumers • Omnivores: eat plants and animals • Carnivores: eat animals (predators) • Insectivores, etc.

  39. Trophic Levels • 4th Level: Decomposers • Bacteria, fungi, other microorganisms

  40. Create a Food Web • http://teacher.scholastic.com/activities/explorer/ecosystems/be_an_explorer/map/foodweb_play.htm

  41. Biomass Pyramid • Biomass pyramid represents the amount of biomass (living material) at each trophic level in an ecosystem. • may not always be shaped as a ‘pyramid’

  42. What are nature’s three most productive and three least productive systems? Figure 3-22

  43. SOIL: A RENEWABLE RESOURCE • Soil is a slowly renewed resource that provides most of the nutrients needed for plant growth and also helps purify water. • Soil formation begins when bedrock is broken down by physical, chemical and biological processes called weathering. • Mature soils, or soils that have developed over a long time are arranged in a series of horizontal layers called soil horizons.


  45. Layers in Mature Soils • Infiltration: the downward movement of water through soil. • Leaching: dissolving of minerals and organic matter in upper layers carrying them to lower layers. • The soil type determines the degree of infiltration and leaching.

  46. Soil Profiles of the Principal Terrestrial Soil Types Figure 3-24

  47. Mosaic of closely packed pebbles, boulders Weak humus-mineral mixture Alkaline, dark, and rich in humus Dry, brown to reddish-brown with variable accumulations of clay, calcium and carbonate, and soluble salts Clay, calcium compounds Desert Soil (hot, dry climate) Grassland Soil semiarid climate) Fig. 3-24a, p. 69

  48. Acidic light-colored humus Iron and aluminum compounds mixed with clay Tropical Rain Forest Soil (humid, tropical climate) Fig. 3-24b, p. 69

  49. Forest litter leaf mold Humus-mineral mixture Light, grayish-brown, silt loam Dark brown firm clay Deciduous Forest Soil (humid, mild climate) Fig. 3-24b, p. 69

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