1. Chapter 23
Global Ecology and Human Interferences

2. Points to Ponder
What is an ecosystem and what are its biotic components?
What are the energy flow and chemical cycling in an ecosystem?
What are the two major ecosystems on earth?
Describe the 3 types of terrestrial ecosystems and the 2 types of aquatic ecosystems.
Compare and contrast food webs and food pyramids.
What is a biogeochemical cycle?
What is a reservoir and an exchange pool.
Explain the water, carbon, nitrogen and phosphorus cycles.
What human activities interfere with these cycles?
What problems are we creating by altering these pathways?
What is ozone depletion and why is this important?
What are the pros and cons to drilling in the Arctic National Wildlife refuge?

3. The nature of ecosystems
Biosphere – the regions of the Earth’s waters, crust and atmosphere inhabited by living organisms
Ecosystem – a place where organisms interact between each other and their environment
Terrestrial: several distinct types based on temperature and waterfall
Aquatic: freshwater and marine

4. Terrestrial ecosystems
23.1 The nature of ecosystems
Terrestrial ecosystems
Forests – dominated by trees
Tropical rain forest
Coniferous forests (taiga)
Temperate deciduous forests
Grasslands – dominated by grass
Tropical grasslands
Temperate grasslands (prairie)
Deserts – characterized by lack of available moisture
Tundra
Deserts

5. Terrestrial ecosystems
23.1 The nature of ecosystems
Terrestrial ecosystems

6. Aquatic ecosystems Marine Freshwater Seashores Oceans Coral reefs
23.1 The nature of ecosystems
Aquatic ecosystems
Marine
Seashores
Oceans
Coral reefs
Estuaries
Freshwater
Lakes
Ponds
Rivers
Streams

7. 23.1 The nature of ecosystems
Aquatic ecosystems

8. Components of an ecosystem
23.1 The nature of ecosystems
Components of an ecosystem
Abiotic components – nonliving environment
Biotic components - living components
Autotrophs – producers
Heterotrophs – consumers
Herbivores – feed on plant and algae
Carnivores – feed on other animals
Omnivores – eat both plants and animals
Detritus feeders – feed on decomposing organic matter
Niche – the role an organism plays in an ecosystem such as how it gets its food, what it eats and how it interacts with other organisms

9. Biotic components of an ecosystem
23.1 The nature of ecosystems
Biotic components of an ecosystem

10. Energy flow and chemical cycling
23.1 The nature of ecosystems
Energy flow and chemical cycling
Energy flow:
Begins and continues when producers absorb solar energy
Occurs as nutrients pass from one population to another
This energy is converted to heat that dissipates into the environment
Only a portion of energy is passed to organisms as they consume one another
Chemical cycling:
Inorganic nutrients are returned to producers from the atmosphere or soil
Chemicals recycle within and between ecosystems

11. Energy flow and chemical cycling
23.1 The nature of ecosystems
Energy flow and chemical cycling

12. Energy flow Food web – describes who eats whom
Grazing food web
Detrital food web
Trophic levels – composed of all organisms that feed at a particular link in the food chain
Producers, primary consumers and secondary consumers
Ecological pyramid – reflects the loss of energy from one trophic level to another
Only about 10% of the energy of one trophic level is available to the next trophic level

13. 23.2 Energy flow
Food webs

14. An example of a food pyramid
23.2 Energy flow
An example of a food pyramid

15. Biogeochemical cycles
23.3 Global Biogeochemical cycles
Biogeochemical cycles
Biogeochemical cycles are pathways by which chemicals circulate through an ecosystem including both living and nonliving components
Water cycle
Carbon cycle
Nitrogen cycle
Phosphorus cycle
Reservoir – fossil fuels, minerals in rocks and sediment in oceans that contain inorganic nutrients that are limited in availability
Exchange pools – atmosphere, soil and water that are ready sources of inorganic nutrients

16. Biogeochemical cycles
23.3 Global Biogeochemical cycles
Biogeochemical cycles

17. 23.3 Global Biogeochemical cycles
Water cycle
Water evaporates from the bodies of water, land and plants and returns when water falls on land to enter the ground, surface waters or aquifers
Human activities that interfere:
Withdraw water from aquifers
Clear vegetation from the land and build structures that prevent percolation and increase runoff
Add pollutants to water such as sewage and chemicals

18. 23.3 Global Biogeochemical cycles
Water cycle

19. 23.3 Global Biogeochemical cycles
Carbon cycle
CO2 is exchanged between the atmosphere and living organisms
Plants incorporate atmospheric CO2 into nutrients through photosynthesis that can be used by living organisms
CO2 is returned to the atmosphere through respiration

20. 23.3 Global Biogeochemical cycles
Carbon cycle

21. Carbon cycle Human activities that interfere:
23.3 Global Biogeochemical cycles
Carbon cycle
Human activities that interfere:
Burning of fossil fuels and the destruction of forests are depositing CO2 to the atmosphere faster than it is being removed
CO2 and other gases (N2O and CH4) are being emitted due to human activities
These gases are called greenhouse gases because they trap heat that contributes to global warming

22. Greenhouse gases and global warming
23.3 Global Biogeochemical cycles
Greenhouse gases and global warming

23. 23.3 Global Biogeochemical cycles
Nitrogen cycle
78% of the atmosphere is nitrogen gas but it is not in a usable form by plants
Nitrogen-fixing bacteria convert nitrogen gas to ammonium that can be used by plants
Nitrifying bacteria convert ammonium to nitrate
Bacteria convert nitrate back to nitrogen gas through a process called dentrification

24. 23.3 Global Biogeochemical cycles
Nitrogen cycle

25. Nitrogen cycle Human activities interfere:
23.3 Global Biogeochemical cycles
Nitrogen cycle
Human activities interfere:
We add nitrogen fertilizers that run off into lakes and streams that causes major fish kills by eutrophication
Burning of fossil fuels
puts nitrogen oxides and sulfur dioxide into the atmosphere where they combine with water vapor to form acids that return to earth as acid deposition
Result in nitrogen oxides and hydrocarbons that react with one another to produce smog

26. 23.3 Global Biogeochemical cycles
Nitrogen cycle

27. 23.3 Global Biogeochemical cycles
Phosphorus cycle
Phosphate ions become available to living organisms by the slow weathering of rocks
Phosphate is a limiting nutrient in ecosystems

28. Phosphorus cycle Human activities interfere:
23.3 Global Biogeochemical cycles
Phosphorus cycle
Human activities interfere:
Runoff of phosphate due to fertilizer and discharge from sewage treatment plants results in eutrophication
Sources of pollution:
Point source – specific sources
Nonpoint sources – runoff from land

29. 23.3 Global Biogeochemical cycles
Sources of pollution

30. Science focus: ozone depletion
23.3 Global Biogeochemical cycles
Science focus: ozone depletion
Ozone shield – a layer of ozone in the stratosphere that absorbs UV rays preventing them from reaching the earth
Causes of depletion:
Chlorine atoms primarily from chlorofluorocarbons(CFCs)
Freon used as a coolant
Cleaning agents
Agents used to make Styrofoam
Concerns about loss of ozone:
Increases mutations leading to skin cancer
Adversely affects the immune system
Impairs crop and tree growth
Can kill off algae and krill that sustain oceanic life

31. Bioethical focus: Oil drilling in the Arctic
23.3 Global Biogeochemical cycles
Bioethical focus: Oil drilling in the Arctic
Should we drill for oil in the Arctic National Wildlife refuge to alleviate the dependence of the US on foreign oil?
Those for drilling:
Yield of a million barrels of oil per day over 20 yrs.
Would affect only a small portion of the Arctic National Wildlife Refuge
New techniques would limit the damage
Increase in Alaskan job and economy
Those against drilling:
We should focus on reducing our need for oil
A modest increase in vehicle fuel efficiency could save more oil than would be gained by drilling
Drilling would not alleviate our needs for oil based on our use
Drilling sites are scattered so roads and such would disrupt even more land
There has been an oil spill from a nearby pipeline so we still have to consider pollution even with newer drilling methods