Ecology and Human Concerns

1
Ecology and Human Concerns

• Chapter 25

2
Ecology
Study of interactions of organisms with one
another and with the physical environment
3
Ecological Terms

• Habitat
• Community
• Niche
• Specialist species
• Generalist species
• Ecosystem

• Succession
• Primary succession
• Secondary succession

4
Simple Ecosystem Model
energy input from sun
PHOTOAUTOTROPHS (plants, other producers)
nutrient cycling
HETEROTROPHS (consumers, decomposers)
energy output (mainly heat)
5
Nature of Ecosystems
Autotrophs Producers Heterotrophs
Consumers Detritivores Decomposers
Omnivores
Tropic Levels 1 - Producers 2 - Herbivores 3 -
Primary carnivores 4 - Secondary carnivores
6
Food Chain
MARSH HAWK

• A straight-line sequence of who eats whom
• Simple food chains are rare in nature

UPLAND SANDPIPER
GARTER SNAKE
CUTWORM
7
FoodWeb
8
Primary Productivity

• Gross primary productivity is ecosystems total
  rate of photosynthesis
• Net primary productivity is rate at which
  producers store energy in tissues in excess of
  their aerobic respiration

9
Ecological Pyramids

• Producers form base
• Biomass pyramid
• Energy pyramid

Energy pyramid for Silver Springs
decomposers/detritivores
top carnivores
21
carnivores
5,060
383
herbivores
3,368
producers
20,810
10
Biogeochemical Cycle

• The flow of a nutrient from the environment to
  living organisms and back to the environment
• Main reservoir for the nutrient is in the
  environment

11
Three Categories

• Hydrologic cycle
• Water
• Atmospheric cycles
• Nitrogen and carbon
• Sedimentary cycles
• Phosphorus and sulfur

12
Hydrologic Cycle
Atmosphere
precipitation onto land 111,000
wind-driven water vapor 40,000
evaporation from land plants (evapotranspiration)
71,000
evaporation from ocean 425,000
precipitation into ocean 385,000
surface and groundwater flow 40,000
Oceans
Land
13
Phosphorus Cycle

• Phosphorus is part of phospholipids and all
  nucleotides
• It is the most prevalent limiting factor in
  ecosystems
• Main reservoir is Earths crust no gaseous phase

14
Phosphorus Cycle
mining
FERTILIZER
excretion
GUANO
agriculture
weathering
uptake by autotrophs
uptake by autotrophs
weathering
LAND FOOD WEBS
DISSOLVED IN OCEAN WATER
MARINE FOOD WEBS
DISSOLVED IN SOIL WATER, LAKES, RIVERS
death, decomposition
death, decomposition
leaching, runoff
sedimentation
settling out
uplifting over geologic time
ROCKS
MARINE SEDIMENTS
15
Human Effects

• In tropical countries, clearing lands for
  agriculture may deplete phosphorus-poor soils
• In developed countries, phosphorus runoff is
  causing eutrophication of waterways

16
Carbon Cycle

• Carbon moves through the atmosphere and food webs
  on its way to and from the ocean, sediments, and
  rocks
• Sediments and rocks are the main reservoir

17
Carbon Cycle
diffusion
Atmosphere
Bicarbonate, carbonate
Terrestrial rocks
Land food webs
Marine food webs
Soil water
Peat, fossil fuels
Marine sediments
18
Carbon in Atmosphere

• Atmospheric carbon is mainly carbon dioxide
• Carbon dioxide is added to atmosphere
• Aerobic respiration, volcanic action, burning
  fossil fuels
• Removed by photosynthesis

19
Greenhouse Effect

• Greenhouse gases impede the escape of heat from
  Earths surface

20
Carbon Dioxide Increase

• Carbon dioxide levels fluctuate seasonally
• The average level is steadily increasing
• Burning of fossil fuels and deforestation are
  contributing to the increase

21
Other Greenhouse Gases

• CFCs - synthetic gases used in plastics and
  refrigeration
• Methane - produced by termites and bacteria
• Nitrous oxide - released by bacteria,
  fertilizers, and animal wastes

22
Nitrogen Cycle

• Nitrogen is used in amino acids and nucleic acids
• Main reservoir is nitrogen gas in the atmosphere

23
Nitrogen Cycle
GASEOUS NITROGEN (N2) IN ATMOSPHERE
NITROGEN FIXATION by industry for agriculture
FOOD WEBS ON LAND
uptake by autotrophs
excretion, death, decomposition
uptake by autotrophs
FERTILIZERS
NO3- IN SOIL
NITROGEN FIXATION
NITROGENOUS WASTES, REMAINS IN SOIL
NH3-, NH4 IN SOIL
2. NITRIFICATION
AMMONIFICATION
NO2- IN SOIL
loss by leaching
loss by leaching
1. NITRIFICATION
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Biological Magnification

• A nondegradable or slowly degradable substance
  becomes more and more concentrated in the tissues
  of organisms at higher trophic levels of a food
  web

25
Human Population Growth

• Population now exceeds 6 billion
• Rates of increase vary among countries
• Average annual increase is 1.26 percent
• Population continues to increase exponentially

26
Side-Stepping Controls

• Expanded into new habitats
• Agriculture increased carrying capacity use of
  fossil fuels aided increase
• Hygiene and medicine lessened effects of
  density-dependent controls

27
Limiting Factors

• Any essential resource that is in short supply
• All limiting factors acting on a population
  dictate sustainable population size

28
Logistic Growth

• As size of the population increases, rate of
  reproduction decreases
• When the population reaches carrying capacity,
  population growth ceases

carrying capacity
Time
29
Density-Dependent Controls

• Logistic-growth equation deals with
  density-dependent controls
• Limiting factors become more intense as
  population size increases
• Disease, competition, parasites, toxic
  effects of waste products

30
Air Pollutants

• Carbon oxides
• Sulfur oxides
• Nitrogen oxides
• Volatile organic compounds
• Photochemical oxidants
• Suspended particles

31
Industrial Smog

• Gray-air smog
• Forms over cities that burn large amounts of coal
  and heavy fuel oils mainly in developing
  countries
• Main components are sulfur oxides and suspended
  particles

32
Photochemical Smog

• Brown-air smog
• Forms when sunlight interacts with components
  from automobile exhaust
• Nitrogen oxides are the main culprits
• Hot days contribute to formation

33
Ozone Thinning

• In early spring and summer, ozone layer over
  Antarctica thins
• Seasonal loss of ozone is at highest level ever
  recorded

34
Effect of Ozone Thinning

• Increased amount of UV radiation reaches Earths
  surface
• UV damages DNA and negatively affects human
  health
• UV also affects plants, lowers primary
  productivity

35
Water Use and Scarcity

• Most of Earths water is too salty for human
  consumption
• Desalinization is expensive and requires large
  energy inputs
• Irrigation of crops is the main use of freshwater

36
Negative Effects of Irrigation

• Salinization, mineral buildup in soil
• Elevation of the water table and waterlogging
• Depletion of aquifers

37
Generating Garbage

• Developed countries generate huge amounts of
  waste
• Paper products account for half the total volume
• Recycling can reduce pollutants, save energy,
  ease pressure on landfills

38
Desertification

• Conversion of large tracts of grassland to
  desertlike conditions
• Conversions of cropland that result in more than
  10 percent decline in productivity

39
Effects of Deforestation

• Increased leaching and soil erosion
• Increased flooding and sedimentation of
  downstream rivers
• Regional precipitation declines
• Possible amplification of the greenhouse effect

40
Regions of Deforestation

• Rates of forest loss are greatest in Brazil,
  Indonesia, Mexico, and Columbia
• Highly mechanized logging is proceeding in
  temperate forests of the United States and Canada

41
Reversing Deforestation

• Coalition of groups dedicated to saving Brazils
  remaining forests
• Smokeless wood stoves have saved firewood in
  India
• Kenyan women have planted millions of trees

42
Fossil Fuels

• Coal, oil, natural gas
• Main energy source of developed countries
• Burning of fossil fuels contributes to global
  warming

43
Nuclear Energy

• Used extensively in some energy-poor developed
  countries
• Little support in the United States
• Emits fewer air pollutants than burning coal, but
  creates radioactive wastes
• Potential for meltdown

44
Chernobyl Accident - 1986

• Core meltdown at a nuclear power plant in the
  Ukraine
• 31 immediate deaths, radiation sickness and death
  for others
• Cloud of radiation spread by winds across Europe
• Long-term health impacts downwind

45
Wind Energy

• An indirect use of solar energy
• Wind farms are arrays of turbines
• Can supplement needs of some regions but is not
  dependable enough on its own

46
Solar-Hydrogen Energy

• Photovoltaic cells use sunlight energy to split
  water
• Hydrogen gas produced in this way can be used as
  fuel or to generate electricity
• Clean, renewable technology

47
Deforestation

• Removal of all trees from large tracts of land
• 38 million acres logged each year
• Wood is used for fuel, lumber
• Land is cleared for grazing or crops