Ecosystems: What Are They and How Do They Work?

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

2. Core Case Study: Tropical Rain Forests Are Disappearing • Cover about 2% of the earth’s land surface • Contain about 50% of the world’s known plant and animal species • Disruption will have three major harmful effects • Reduce biodiversity • Accelerate global warming • Change regional weather patterns

3. Natural Capital Degradation: Satellite Image of the Loss of Tropical Rain Forest Santa Cruz, Boliva: June 1975 May 2003

4. 3-1 What Is Ecology? • Concept 3-1 Ecology is the study of how organisms interact with one another and with their physical environment of matter and energy.

5. Cells Are the Basic Units of Life • Cell Theory – theory that all living things are composed of cells • Eukaryotic cell – membrane, nucleus, organelles • Prokaryotic cell – membrane • bacteria

6. (a) Eukaryotic Cell (b) Prokaryotic Cell Energy conversion DNA (no nucleus) Nucleus (DNA) Protein construction Cell membrane Cell membrane Protein construction and energy conversion occur without specialized internal structures Stepped Art Fig. 3-2, p. 52

7. Species Make Up the Encyclopedia of Life • Species • 1.75 Million species identified • Insects make up most of the known species • Perhaps 10–14 million species not yet identified • www.eol.org project started in 2007 to list and describe all identified species.

8. Ecologists Study Connections in Nature • Ecology – study of how organisms interact with biotic and abiotic factors in their environment • Levels of organization • Population – same species in same place at same time: ex. Field mice living in a cornfield • Genetic diversity – variations in population • Community – all populations of different species living in same place • Ecosystem – community of different species interacting w/ one another & w/ nonliving environment • Biosphere – parts of Earth’s air, water, & soil where life if found

9. Parts of the earth's air, water, and soil where life is found Biosphere A community of different species interacting with one another and with their nonliving environment of matter and energy Ecosystem Populations of different species living in a particular place, and potentially interacting with each other Community Population A group of individuals of the same species living in a particular place An individual living being Organism The fundamental structural and functional unit of life Cell Chemical combination of two or more atoms of the same or different elements Molecule Smallest unit of a chemical element that exhibits its chemical properties Atom Stepped Art Fig. 3-3, p. 52

10. Population of Glassfish in the Red Sea

11. Genetic Diversity in a Caribbean Snail Population

12. Science Focus: Have You Thanked the Insects Today? • Insects play a vital role in sustaining life on Earth • Pollinators • Eat other insects • Loosen and renew soil • Scientists estimate the value of ecological services provided by insects in U.S. at $57 billion per year • Reproduce rapidly • Very resistant to extinction • Insects don’t need humans, but we most certainly need them

13. Importance of Insects Pollinator Pest Controller

14. 3-2 What Keeps Us and Other Organisms Alive? • Concept 3-2 Life is sustained by the flow of energy from the sun through the biosphere, the cycling of nutrients within the biosphere, and gravity.

15. The Earth’s Life-Support System Has Four Major Components • Atmosphere • Troposphere • Stratosphere • Hydrosphere – liquid, gas, solid (permafrost too) • Geosphere – core, mantle, crust • Biosphere – thin layer of Earth ~ 9km thick

16. Vegetation and animals Atmosphere Biosphere Soil Rock Crust Lithosphere Mantle Biosphere (living organisms) Atmosphere (air) Core Crust (soil and rock) Mantle Hydrosphere (water) Geosphere (crust, mantle, core) Fig. 3-6, p. 55

17. Life Exists on Land and in Water • Biomes – large regions w/ distinct climate & species (especially plants) adapted to live there • Aquatic life zones • Freshwater life zones • Lakes and streams • Marine life zones • Coral reefs • Estuaries • Deep ocean

18. Major Biomes along the 39th Parallel in the U.S.

19. Three Factors Sustain Life on Earth • One-way flow of high-quality energy beginning with the sun – through living things via feeding – into environment as low quality energy (heat dispersed to air or water) – eventually back into space as heat • No round trips – high quality energy cannot be recycled • Cycling of matter or nutrients throughout biosphere • Earth a closed system (essentially fixed supply of nutrients) • Nutrients are recycled • Gravity • Allows planet to hold onto atmosphere • Enables movement & cycling of materials

20. What Happens to Solar Energy Reaching the Earth? • UV, visible, and IR energy • Radiation • Absorbed by ozone • Absorbed by the earth • Reflected by the earth • Radiated by the atmosphere as heat • Natural greenhouse effect

21. Flow of Energy to and from the Earth

22. Active Figure: Energy flow

23. Animation: Energy flow in Silver Springs

24. Active Figure: Energy flow from the Sun to Earth

25. 3-3 What Are the Major Components of an Ecosystem? • Concept 3-3A Ecosystems contain living (biotic) and nonliving (abiotic) components. • Concept 3-3B Some organisms produce the nutrients they need, others get their nutrients by consuming other organisms, and some recycle nutrients back to producers by decomposing the wastes and remains of organisms.

26. Ecosystems Have Living and Nonliving Components • Abiotic • Water • Air • Nutrients • Rocks • Heat • Solar energy • Biotic • Living and once living, also waste products

27. Major Biotic and Abiotic Components of an Ecosystem

28. Range of Tolerance for a Population of Organisms INSERT FIGURE 3-10 HERE Range of tolerance for a population of organisms, such as fish, to an abiotic environmental factor—in this case, temperature. These restrictions keep particular species from taking over an ecosystem by keeping their population size in check

29. Several Abiotic Factors Can Limit Population Growth • Limiting factor principle • Too much or too little of any abiotic factor can limit or prevent growth of a population, even if all other factors are at or near the optimal range of tolerance • Water or lack thereof will limit plant growth in a desert • Soil nutrients can limit types of plants • DO in aquatic ecosystems • Salinity in aquatic ecosystems

30. Producers and Consumers Are the Living Components of Ecosystems (1) • Trophic (feeding) levels • Producers, autotrophs • Photosynthesis • 6CO2 + 6H2O + solar energy C6H12O6 + 6O2 • Chemosynthesis • Plants, phytoplankton, algae • Consumers, heterotrophs • Primary - herbivores • Secondary - carnivores • Third and higher level • Decomposers – recycle nutrients • Certain types of bacteria & fungi

31. Producers and Consumers Are the Living Components of Ecosystems (2) • Detritivores • Feed on wastes or dead bodies of other organisms • Mites, earthworms, catfish, vultures • Aerobic respiration C6H12O6 + 6O2 6CO2 + 6H2O + ENERGY • Anaerobic respiration, fermentation End products could be methane gas, ethyl alcohol, acetic acid, or hydrogen sulfide

32. Detritivores and Decomposers on a Log Various detritivores and decomposers (mostly fungi and bacteria) can “feed on” or digest parts of a log and eventually convert its complex organic chemicals into simpler inorganic nutrients that can be taken up by producers.

33. Energy Flow and Nutrient Cycling Sustain Ecosystems and the Biosphere • One-way energy flow • Nutrient cycling of key materials

34. The Main Structural Components of an Ecosystem Natural capital: the main structural components of an ecosystem (energy, chemicals, and organisms). Nutrient cycling and the flow of energy—first from the sun, then through organisms, and finally into the environment as low-quality heat—link these components.

35. Science Focus: Many of the World’s Most Important Species Are Invisible to Us • Microorganisms • Bacteria • Protozoa • Fungi • phytoplankton • Some are harmful • Most are beneficial • Break down food we digest • Purify water • Produce food like bread, cheese, soy sauce

36. Active Figure: Roles of organisms in an ecosystem

37. 3-4 What Happens to Energy in an Ecosystem? • Concept 3-4A Energy flows through ecosystems in food chains and webs. • Concept 3-4B As energy flows through ecosystems in food chains and webs, the amount of chemical energy available to organisms at each succeeding feeding level decreases.

38. Energy Flows Through Ecosystems in Food Chains and Food Webs • Food chain • Food web

39. A Food Chain A food chain. The arrows show how chemical energy in nutrients flows through various trophic levels in energy transfers; most of the energy is degraded to heat, in accordance with the second law of thermodynamics. See an animation based on this figure at CengageNOW. Question: Think about what you ate for breakfast. At what level or levels on a food chain were you eating?

40. Simplified Food Web in the Antarctic Greatly simplified food web in the Antarctic. Many more participants in the web, including an array of decomposer and detritus feeder organisms, are not depicted here. Question: Can you imagine a food web of which you are a part? Try drawing a simple diagram of it.

41. Usable Energy Decreases with Each Link in a Food Chain or Web • Biomass • Ecological efficiency • Pyramid of energy flow

42. Usable energy available at each trophic level (in kilocalories) Heat Tertiary consumers (human) 10 Heat Secondary consumers (perch) 100 Heat Decomposers Heat Primary consumers (zooplankton) 1,000 Heat 10,000 Producers (phytoplankton) Generalized pyramid of energy flow showing the decrease in usable chemical energy available at each succeeding trophic level in a food chain or web. In nature, ecological efficiency varies from 2% to 40%, with 10% efficiency being common. This model assumes a 10% ecological efficiency (90% loss of usable energy to the environment, in the form of low-quality heat) with each transfer from one trophic level to another. Question: Why is a vegetarian diet more energy efficient than a meat-based diet? Stepped Art Fig. 3-15, p. 63

43. Some Ecosystems Produce Plant Matter Faster Than Others Do • Gross primary productivity (GPP) • rate at which ecosystem’s producers convert solar energy into chemical energy as biomass (their tissues) • measured in energy production per unit area over time kcal/m2/year • Net primary productivity (NPP) = GPP-R • To stay alive, grow, & reproduce, producers must use some of they energy stored in their biomass (R) • Rate at which producers use photosynthesis to produce & store chemical energy minus the rate they use some of their stored energy through respiration • Ecosystems and life zones differ in their NPP • NPP = biomass available as nutrients for consumers

44. Estimated Annual Average NPP in Major Life Zones and Ecosystems Estimated annual average net primary productivity in major life zones and ecosystems, expressed as kilocalories of energy produced per square meter per year (kcal/m2/yr). Question: What are nature’s three most productive and three least productive systems? (Data from R. H. Whittaker, Communities and Ecosystems, 2nd ed., New York: Macmillan, 1975)

45. Animation: Prairie food web

46. Active Figure: Rainforest food web

47. Animation: Diet of a red fox

48. Animation: Prairie trophic levels

49. 3-5 What Happens to Matter in an Ecosystem? • Concept 3-5 Matter, in the form of nutrients, cycles within and among ecosystems and the biosphere, and human activities are altering these chemical cycles.

50. Nutrients Cycle in the Biosphere • Biogeochemical cycles, nutrient cycles • Hydrologic • Carbon • Nitrogen • Phosphorus • Sulfur • Connect past, present , and future forms of life