1. Ecosystems
Chapters 55 & 56

2. Ecosystems
All abiotic factors & species

3. ▼ A desert spring ecosystem
ecosystems
◀ An island ecosystem
▼ A desert spring ecosystem
Figure 55.2 Ecosystems at different scales

4. Ecosystems Processes in the ecosystems 1. Energy
Comes from sun
Photosynthesis(chemical energy)
2. Biogeochemical cycles(nutrients)
Chemicals that move through ecosystems
Mostly found in nonliving reservoirs

5. Microorganisms and other detritivores
Sun
Key
Chemical cycling Energy flow
Loss of heat
Primary producers
Primary consumers
Detritus
Figure 55.4 An overview of energy and nutrient dynamics in an ecosystem
Microorganisms and other detritivores
Secondary and
tertiary consumers

6. Ecosystems Photosynthesis
Decomposition & respiration return elements to abiotic forms
Elements are recycled
Energy is released as heat
Sun continuously supplies energy
Evaporation & precipitation circulate elements

7. Trophic levels Energy flow through the ecosystem
Autotrophs: primary producers
Heterotrophs: consumers
Primary consumers: herbivores
Secondary consumers: carnivores
Decomposers: break down organic matter
Detritivore: live on refuse of ecosystem

8. Trophic levels “trophos” means feeder All levels feed on another
Food chain
Represents these levels
Food web:
More complex relationships between levels

9. Figure 55.1 How can a fox transform a grassland into tundra?

10. Figure 55. 1a How can a fox transform a grassland into tundra
Figure 55.1a How can a fox transform a grassland into tundra? (part 1: fox with seabird)

11. ▼ Fungi decomposing a dead tree
Decomposers
▼ Fungi decomposing a dead tree
Figure 55.3 Detritivores
▲ Rod-shaped and spherical bacteria in compost (colorized SEM)

12. Food chain

13. Food chain

14. Food web

15. Energy flow Primary productivity:
Amount of energy produced by photosynthesis (organic matter) in a community
Biomass:
Total mass of organisms in an ecosystem
Rainforests or wet lands have a high productivity

16. Energy flow Secondary productivity Rate of biomass of heterotrophs
Less than primary due to
1. Not all plants are consumed by herbivores
2. Some energy of herbivores is passed as waste
3. Some energy is lost as heat

17. Energy flow

18. Energy flow Gross primary production (GPP)
Amount light energy converted to chemical energy over time
Net primary production (NPP)
GPP less the amount of energy for plant cellular respiration (R)
NPP= GPP-R

19. 1 2 3 Net primary production (kg carbon/m2·yr) · Energy flow
Figure 55.6 Global net primary production in 2002
Net primary production (kg carbon/m2·yr) 1 2 3

20. Energy flow in food chains
Ecological pyramids
Relationship of energy, biomass or numbers in an ecosystem
The limit is based on amount of sunlight and nutrients available

21. Ecological pyramids

22. Ecological pyramids

23. Ecological pyramids

24. Ecological pyramids

25. Water cycle Oceans cover ¾ of earth’s surface
Sun powers evaporation of water from oceans
90% of water in atmosphere over land comes from plant transpiration
Most falls over the ocean as rain
2% is frozen in ice
Water supplies the hydrogen in ATP formation

26. Water cycle

27. Carbon cycle Photosynthesis uses up about 10% of atmospheric CO2
Respiration replaces CO2 in the air
Most CO2 is in fossil fuels, coals, gas
Use of these is increasing CO2 in the atmosphere

29. Carbon cycle

30. Nitrogen cycle Prokayotes “fix” nitrogen to usable form
Nitrogen is being added to the system by fertilizers

31. Nitrogen cycle

32. Phosphorus cycle Exist in mineral form (not atmosphere)
Need for ATP, phospholipids, DNA, RNA
Fertilizers adding a lot

33. Phosphorus cycle

34. Ecosystem stabilization
More diverse species (species richness)
1. Ecosystem productivity
2. Spatial heterogencity
More habitat variation (soils, topography) allows more areas for animals to live
3. Climate
More stable the weather the greater the species

35. Biodiversity hotspots

36. Biodiversity

37. Biodiversity 1. Genetic diversity 2. Species diversity
3. Ecosystem diversity

38. Threats to Biodiversity
Habitat loss
Introduced species
Overexploitation

39. Problems Pollution Rhine river (Mercury, pesticides 1986)
DDT (chlorinated hydrocarbons)
Absorbed in animal fats
Biological magnification:
Become more concentrated in food chain

40. DDT

41. Acid rain Sulfur dioxide Forms sulfuric acid when comes with rain
Lowers pH
Kills wildlife

42. Acid rain

43. Farming

44. Ozone layer Protects against UV Thinning 1975
Chloroflurocarbons (CFC’s)
Increased melanoma

45. Ozone

46. Ozone

47. Greenhouse effect Increased carbon dioxide & other gases
Reflects heat from earth
Keeping it in the atmosphere
Global warming

48. Greenhouse effect

49. Effect of warming Plants/animals further north Migratory changes
Species have problems adapting
Increasing sea level
Retreating glaciers
More severe weather changes

50. Logging

51. Conservation Conservation Biology: Attempts to conserve biodiversity
Restoration Ecology:
Return ecosystems to natural state