Chapter 3

1. Chapter 3 Ecosystems: What are they and how do they work?

2. Ecology • “Study of how organisms interact with one another and with their nonliving environment” • “Connections in nature” • Ecology focuses on: organisms, populations, communities, ecosystems, and biosphere

3. Perspective

4. Small scale • Organism: any form of life • Multi-celled and single-celled • Species: “groups of organisms that resemble one another in appearance, behavior, chemistry, and genetic makeup” • 1.4 million named/identified species • Probably 4-100 million total species

5. Large scale • Population: “a group of interacting individuals of the same species occupying a specific area” • Genetic diversity – variations in genetic makeup • Habitat – where the population lives • Distribution / range: area the species covers • Community: all populations of different species in the same area • Ecosystem: where populations interact with their living and non-living environment • Natural or artificial • Biosphere: all of earth’s ecosystems(all life on earth)

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

7. Earth’s spheres • Atmosphere: air around earth • Troposphere: inner layer of atmosphere – most air is here (78% nitrogen, 21% oxygen) • Stratosphere: upper layer of atmosphere – contains ozone • Hydrosphere: all of earth’s water • Liquid water • Ice • Water vapor • Lithosphere: earth’s crust and upper mantle • Biosphere: all life on earth

8. Life sustaining processes • Flow of energy • Sun and other organisms (feeding) go in as high-quality energy • Continue flow as low-quality energy • Back to space as heat • Cycling of matter: C, N, P cycles • Gravity

9. The sun! • Sun  earth (through electromagnetic waves) • Plants/bacteria take in energy to make food  other organisms eat photosynthetic organisms • Energy from the sun drives other systems on earth, like weather and water • 1/1x109 of the sun’s energy makes it to earth • Most of the E is reflected back • 80% warms troposphere andcycles water • 1% generates wind • <0.1% is used for photosynthesis

10. 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

11. Greenhouse gasses • H2O, CO2, CH4, N2O, O3 • Larger-wavelength light waves are absorbed and re-emitted by these molecules, heating them up • Natural greenhouse effect keeps us warm (moon is 107 C in the day, -153 C at night) • Ozone keeps some harmful UV rays away • Human-produced greenhouse gasses add to the effect

12. Biomes and aquatic life zones • Biomes: “large regions… with distinct climates and specific species (especially vegetation) adapted to them” • Forests, deserts, grasslands, tundra, etc • Aquatic life zones: watery parts of the biosphere • Freshwater life zones • Ocean/marine life zones

13. Components of ecosystems • Abiotic: nonliving components – air, water, nutrients, solar E • Biotic: consists of living components • Producers: photosynthetic plants and bacteria • Consumers: eat producers/other consumers • Decomposers: break down dead organisms • Range of tolerance: extremities of theconditions that a population can live • Members within a population will have variation in range of tolerance

14. Limits to population growth • Limiting factor: what is holding something back • 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 optimum range of tolerance” • Precipitation • Nutrients • Temperature

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

16. Producers! • Producers = autotrophs • Photoautotroph • Chemoautotroph • Make their own food • Land = plants (mostly) • Water = phytoplankton (mostly) • Photosynthesis: CO2 + H2O  C6H12O6 + O2 • Chemosynthesis: make food from chemical E (bacteria near hydrothermal vents use H2S)

17. 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

18. Consumers • Heterotrophs: get energy from other organisms • Primary: herbivores; directly eat producers • Secondary: eat primary consumers • Third and further level: eat secondary or higher consumers • Omnivores: eat plants and animals

19. Decomposers • Passively “eat” dead organic matter • Dentritivores: “insects and other scavengers that feed on the wastes or dead bodies of other organisms” • Very important to our ecosystem • Examples: • Bacteria • Fungi • Worms

20. Aerobic and anaerobic respiration • Aerobic respiration: oxygen burns organic nutrients into CO2 and H2O • C6H12O6 + 6O2 6CO2 + 6H2O + E • Anaerobic respiration: breaking down organic compounds without oxygen; fermentation • Instead of CO2 and H2O, end results are methane, ethyl alcohol, acetic acid, and hydrogen sulfide

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

22. Biodiversity • Biodiversity: “renewable resource” • Four components: • Functional diversity – bio and chem processes • Ecological diversity – variety of ecosystems • Genetic diversity – variety of genetic material in a species/population • Species diversity – variety of species in different habitats

23. Biodiversity loss • HIPPO!!! • Habitat destruction and degradation • Invasive species • Pollution • Population growth (human) • Overexploitation (overhunting, overconsumption) • Why care? • Two approaches: • Ecosystem approach – protect populations of species in their natural habitats • Species approach – protect species from premature exticntion

24. The Ecosystem Approach The Species Approach Goal Goal Protect populations of species in their natural habitats Protect species from premature extinction Strategy Strategies Preserve sufficient areas of habitats in different biomes and aquatic systems • Identify endangered • species • Protect their critical • habitats Tactics Tactics • Protect habitat areas • through private purchase or government action • Legally protect • endangered species • Manage habitat • Eliminate or reduce • populations of nonnative species • from protected areas • Propagate endangered • species in captivity • Manage protected areas to sustain native species • Reintroduce species into • suitable habitats • Restore degraded • ecosystems Fig. 3-16, p. 63

25. Energy flow in ecosystems • Little matter is wasted in ecosystems •     • Food chain – energy and nutrients move through an ecosystem • Trophic level: where a species falls on a food web • Food web – shows more connections than chain, relations between species

26. First Trophic Level Second Trophic Level Third Trophic Level Fourth Trophic Level Tertiary consumers (top carnivores) Secondary consumers (carnivores) Producers (plants) Primary consumers (herbivores) Heat Heat Heat Solar energy Heat Heat Heat Heat Detritivores (decomposers and detritus feeders) Heat Fig. 3-17, p. 64

27. Humans Blue whale Sperm whale Crabeater seal Elephant seal Killer whale Leopard seal Adelie penguins Emperor penguin Squid Petrel Fish Carnivorous plankton Krill Herbivorous plankton Phytoplankton Fig. 3-18, p. 65

28. Energy flow • Biomass – dry weight of all organic matter in organisms of a food chain/web • Each time E is transferred, heat energy is lost • Ecologic efficiency – usually about 10%, can be between 2% and 40%

29. Heat Heat Tertiary consumers (human) Decomposers Heat 10 Secondary consumers (perch) Heat 100 Primary consumers (zooplankton) 1,000 Heat Producers (phytoplankton) 10,000 Usable energy Available at Each tropic level (in kilocalories) Fig. 3-19, p. 66

30. Productivity • Gross primary productivity (GPP) – “the rate at which an ecosystem’s producers convert solar energy into chemical energy” • Net primary productivity (NPP) – “the rate at which producers use photosynthesis to store energy minus the rate at which they use some of this stored energy” • NPP = GPP – R (energy used in respiration) • NPP limits number of consumers • Humans use/waste/destroy 27% of earth’s potential NPP • Humans, pets, and livestock make up 98% of earth’s vertebrate biomass

31. Gross primary productivity (grams of carbon per square meter) Fig. 3-20, p. 66

32. Sun Photosynthesis Energy lost and unavailable to consumers Respiration Gross primary production Net primary production (energy available to consumers) Growth and reproduction Fig. 3-21, p. 66

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

34. Soil • Soil – eroded rock, mineral nutrients, decaying organic matter, water, air, and organisms • Weathering – rock breaking down into fragments and particles by physical, chemical, and biological processes • Support for plants and other life, filters water, and helps remove CO2 • Humans have accelerated natural soil erosion • 1/3 to 1/2 of world’s croplands are losing topsoil faster than it’s being renewed naturally

35. Soil layers • “Soil horizons” • Soil profile  • O horizon – organic material • A horizon – “humus” = partially decomposed plants and animals • B and C horizon – inorganic material • Pores contain air and water • Infiltration – water moving down through the soil • Leaching – water dissolves minerals and organic matter and seeps down in the soil

36. Wood sorrel Oak tree Organic debris builds up Lords and ladies Dog violet Rock fragments Grasses and small shrubs Earthworm Millipede Moss and lichen Fern Honey fungus O horizon Mole Leaf litter A horizon Topsoil B horizon Bedrock Subsoil Immature soil Regolith Young soil C horizon Pseudoscorpion Mite Parent material Nematode Root system Actinomycetes Red Earth Mite Fungus Mature soil Bacteria Springtail Fig. 3-23, p. 68

37. Some Soil Properties • Soils vary in the size of the particles they contain, the amount of space between these particles, and how rapidly water flows through them. Figure 3-25

38. Soil properties • Soil texture • Clay particles = small • Silt particles = medium • Sand particles = large • Loam = mix of all three, best for growing plants

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

40. Matter cycling • Nutrients – “elements and compounds that organisms need to live, grow, and reproduce” • Biogeochemical cycles aka nutrient cycles • Driven by solar E and gravity

41. Water cycle • AKA hydrologic cycle • Powered by gravity and E from sun • About 84% water vapor from oceans • Where does the water go? • Glaciers • Aquifers • Surface runoff – streams  lakes  oceans • Runoff causes natural erosion • Carries nutrients in/between ecosystems • Water is naturally purified in the water cycle • Cycle of natural renewal of water quality

42. Water’ Unique Properties • There are strong forces of attraction between molecules of water. • Water exists as a liquid over a wide temperature range. • Liquid water changes temperature slowly. • It takes a large amount of energy for water to evaporate. • Liquid water can dissolve a variety of compounds. • Water expands when it freezes.

43. Effects of humans on the water cycle • Withdraw large amounts of freshwater from rivers, lakes, and underground, sometimes faster than it is replaced • Clearing land / destroying wetland • Increases runoff – more chemicals and erosion • Reduces ability to refill groundwater supplies • Increases potential to flood • Adding nutrients and pollutants • Warmer climate (global warming) is causing the water cycle to speed up • Change weather patterns • Intensify global warming

44. Carbon cycle • Based on CO2 • CO2 helps regulate temperature on earth • Producers remove CO2, consumers put it back into the cycle • Long-term carbon sinks • Oil deposits • Marine shells • Human effects • Clear more vegetation than can grow back, which reduces the CO2 taken out of the atmosphere • Burn oil/wood which puts more CO2 into the atmosphere

45. Effects of Human Activities on Carbon Cycle • We alter the carbon cycle by adding excess CO2 to the atmosphere through: • Burning fossil fuels. • Clearing vegetation faster than it is replaced. Figure 3-28

46. Nitrogen cycle • N is an important element to some organic molecules (nucleic acids and amino acids) • Nitrogen is “fixed” by bacteria (or lightning), turning N2 into NH3 (plants can take up NH4+) • NH3 can be turned into NO2- (harmful to plants) into NO3- (helpful to plants) by other bacteria • Decomposers convert N in organic compounds back into NH3 • Yet more bacteria can turn NH3 back into N2 or N2O

47. Effects of humans on the nitrogen cycle • Add large amounts of NO into atmosphere when we burn fuels at high temps, which can turn into NO2, which can turn into HNO3 (acidic) • Livestock and fertilizer adds N2O to the atmosphere (bacteria breaking down waste) which can deplete ozone or warm atmosphere • NO3- from fertilizers can contaminate ground water • Destroying plants releases more N into the atmosphere • Agricultural and sewage runoff changes nitrate levels in aquatic ecosystems • Harvesting or irrigating N-rich crops remove N from soil

48. Phosphorus cycle • Phosphorus needed in DNA and ATP • Slow cycle, little P circulates in atmosphere, flows mostly from land into oceans • P is typically found in salts (with PO43-) in rocks • PO43- from rocks wash into oceans, get deposited as sediment, and will show up millions of years later as rocks shift back to surface • Plants get PO43- from soil (usually a limiting growth factor) and we get P from plants, and waste P leaves us in urine • PO43--salts are not very soluble in water, so aquatic plant life is limited by P levels

49. Effect of humans on phosphorus cycle • Mining for PO43- for fertilizers removes large quantities in a short period • Destruction of tropical forests decreases amount of PO43- available in tropical soil • PO43- runoff from fertilizers, livestock, and sewage disrupts aquatic systems

50. Sulfur cycle • A lot of sulfur is in rocks underground or in (SO42-) salts under ocean sediments • H2S (toxic) released form volcanoes (as is SO2) and some organic matter broken down by decomposers • SO42- can enter the atmosphere from sea spray, dust storms, and forest fires • Plants absorb SO42- from the soil to use for some proteins • Some marine algae produce CH3SCH3 which can form the starting points for cloud condensation • SO2 and SO3 in the air can make H2SO4 (acidic) • In anaerobic environments, SO42- can be converted to S2- where it can react with metals to be deposited as rock