How ecosystems work.

1. Chapter 5
How Ecosystems Work

2. Lake Victoria
 Freshwater lake in Africa
 Formerly home to ≈ 400 species of cichlids
 1960: Nile perch
introduced
 1990: water hyacinth
invaded
 Today, ecological
imbalance; why?

3. What Is Ecology?
 Literally study of one’s “house”
 Interactions
 Two components
 Biotic
 Abiotic
 Broadest biological field of study

4. Ecological Organization
 Organism
 Population
 Community
 Ecosystem
 Landscape
 Biosphere

5. Goals Of Ecologists
 Understand how ecosystems function
 Make connections: landscape ecology
 Connections among ecosystems
 Great blue heron

6. Energy
 Capacity or ability to do work
 Flows through ecosystems
 Why do organisms need energy?
 Different kinds
Potential energy Kinetic energy

7. First Law of Thermodynamics
 Energy cannot be
created or
destroyed
 Energy can be
changed from one
form to another

8. Second Law of
Thermodynamics
 When energy is changed from one form
to another, some is degraded into heat
 Heat is a less usable form of energy
 Increases entropy in the universe

9. Ecosystem Composition
 Producers
 Consumers
 Decomposers

10. Producers
 Make their own food
 Photosynthesis
 Examples?
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11. Consumers
 Feed on other things
 Herbivores
 Carnivores
 Omnivores
 Detrivores

12. Decomposers
 Break down dead organisms and waste
products
 Examples?

13. Energy Flow
 Energy passes from one organism to the
next
 Trophic level: each step in this flow of
energy
 Food chain: straight path
 Food web
 Interconnected food chains
 More realistic than food chain; why?

14. Food Chain

15. Food
Web

16. Biogeochemical Cycles
 Matter cycles through ecosystems
 Five cycles
 Carbon
 Hydrologic (water)
 Nitrogen
 Sulfur
 Phosphorus

17. Carbon Cycle
 Essential component for life
 Gas (CO2) in atmosphere
 Several forms in ocean
 Can take a long time—think fossil fuels
Photosynthesis Cellular respiration
CO2 Sugar CO2

18. Carbon Cycle

19. Hydrologic Cycle
Ocean Atmosphere Land Ocean

20. Nitrogen Cycle
 Proteins, DNA
 Atmosphere is 78% N2
 Five steps
 Nitrogen fixation
 Nitrification
 Assimilation
 Ammonification
 Denitrification

21. Nitrogen Fixation
 Specialized bacteria
 Split atmospheric nitrogen and combine it
with hydrogen

22. Nitrogen Cycle

23. Sulfur Cycle
 Underground sedimentary rocks and
minerals
 Erosion releases compounds to ocean
 Volcanoes
 Essential component of proteins

24. Sulfur Cycle

25. Phosphorus Cycle
 No atmospheric component
 Phosphates used in DNA and ATP
(chemical energy)
 Phosphates move through the food chain
Land Organism Organism Land

26. Phosphorus Cycle

27. Ecological Niche
 Everything about an organism
 Adaptations
 Use of resources
 Lifestyle
 Habitat

28. Ecological Niche
 Two species cannot occupy the same
niche: why?
 Resource partitioning
 Reduces niche overlap
 Reduces competition

29. Resource Partitioning At Work!

30. Species Interactions
 No species lives in complete isolation
 Symbiosis
 Intimate relationship between members
of at least 2 species
 Mutualism, commensalism, parasitism
 Result of coevolution
 Other interactions
 Predation, competition

31. Mutualism
 Both species benefit

32. Commensalism
 One species benefits, other not affected

33. Parasitism
 Parasite benefits, host is “harmed”
 Ectoparasites & endoparasites

34. Species Interactions
 Predation: consumption of one species by
another
 Coevolution: “arms race”

35. Avoiding Predators
 Mechanical defenses
 Social groups
 Camouflage
 Protective chemicals

36. Species Interactions
 Competition: two or more organisms
attempting to use the same resource
 Intraspecific vs. interspecific

37. Keystone Species
 Crucial to maintenance of an ecosystem
 Loss affects many other
species
 Examples?
 This idea is being
challenged; why?

38. Case Study:
Global Climate Change
 Atmospheric CO2 increased dramatically.
Why?
 10 warmest years have occurred since 1990
 2005 warmest
 1998 second warmest
 2002 third warmest
 Earth’s temperatures may rise 1.8o – 4.0o C
(3.2o – 7.2o F) by end of 21st century
 What could occur?

39. Case Study:
Global Climate Change
 Kyoto Protocol – International climate change conference
– Kyoto, Japan 1997
 Highly developed countries to cut
CO2 emissions ~ 5.2% by 2012
 US Department of Energy
 Automotive vehicles
designed for better gas
mileage
 High efficiency wind
turbines