1. DP Environmental systems
and societies
Topic 2
The ecosystem

2. 2.5 FUNCTION

4. Ecosystem function
• Producers, consumers, and
decomposers all have their part to
play in cycling materials and energy
in the ecosystem

5. Energy cycles

7. Material cycles
• Refer to Topic 1 ppt
Also
• Photosynthesis
• Photosynthesis and respiration
• Carbon cycle

8. Nitrogen in
the air
animal protein
dead plants & animals
urine & faeces
ammonia
nitrites
nitrates
plant made
protein
dead rabbit
decomposition by bacteria & fungi
bacteria
(nitrifying bacteria)
nitrates absorbed
denitrifying
bacteriaroot nodules
(containing nitrogen
fixing bacteria)
nitrogen fixing
plant
eg pea, clover
bacteria
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9. Terminology
Primary productivity – the gain by
producers (autotrophs) in energy or
biomass per unit area per unit time
Secondary productivity – the biomass
gained by heterotrophic organisms
through feeding or absorption

10. Terminology
Gross productivity (GP) – the total gain
in energy or biomass per unit area
per unit time
Gross primary productivity (GPP) - GP
of primary producers
Gross secondary productivity (GSP) –
GP absorbed in consumers

11. Terminology
Net productivity (NP) – the gain in
energy or biomass per unit area
per unit time after allowing for
respiratory losses (R).
Net primary productivity (NPP) – NP
for producers NPP = GPP – R.
Net secondary productivity (NSP) –
NP for consumers NSP = GSP – R.

12. • Would you consider
open ocean or
tropical rainforest to
be the most
productive? Why?
• (consider area)

13. Is this primary or
secondary
productivity?
Gross or net
productivity?
Biomass or
energy?

14. 2.6 CHANGES

16. Limiting factors
• Temperature

17. Limiting factors
• Food source

18. Limiting factors
Density dependent
(negative feedback)
• Competition for
resources
• Space
• Disease
• Parasitism
• Predation
• Population size
Density independent
• Extremes of weather
• Long-term climate
change
• Volcanoes and
tsunamis

19. S and J curves - animation

20. r strategists
K strategists

21. r strategists K strategists
Initial colonizers Dominant species
Large numbers of a few
species
Diverse range of
species
Highly adaptable Generalists
Rapid growth and
development
Slow development
Early reproduction Delayed reproduction
Short life Longer living
Small size Larger size
Very productive Less productive

22. 2.6.5 Succession

23. Succession 繼承法
Predictable changes in a community
Knowing what animals and plants will
dominate next

24. Primary succession
A series of changes that occurs where no organisms
exist

25. Pioneer species
The first species in primary succession
Pioneer species

26. Secondary succession
A series of changes that occurs when there are
organisms to begin with

27. Secondary succession
A series of changes that occurs when there are
organisms to begin with

28. Figure 53.18 Patchiness and recovery following a large-scale disturbance

29. Figure 53.18x1 Large-scale disturbance: Mount St. Helens

30. Figure 53.18x2 Forest fire

31. Figure 53.19 A glacial retreat in southeastern Alaska

32. Table 53.2 The Pattern of Succession on Moraines in Glacier Bay

33. Figure 53.20 Change in soil nitrogen concentration during succession after glacial retreat in Glacier Bay, Alaska

34. Figure 53.20 Alders and cottonwoods covering the hillsides

35. Figure 53.20 Spruce coming into the alder and cottonwood forest

36. Figure 53.20 Spruce and hemlock forest

37. Terminology
Zonation – different to succession –
difference due to environmental
gradient (eg. altitude)
Succession occurs over several seral
stages where each sere is a set of
communities.
Plagiosere – humans prevent a
climax community – growing crops

38. Hydrosere (water)

39. Lithosere (rock) – one type of xerosere (land)

40. Psammosere (sand) – one type of xerosere
(land)

41. Climax community
• Greater biomass
• Higher levels of diversity
• Better soil conditions
• Better soil structure
• Lower pH
• Taller and longer living plants
• More K less r strategists
• More complexity and stability
• More habitat diversity
• Steady state equilibrium
• Production:respiration ratio P/R reaches 1
(not ideal for agriculture)

42. 2.7 MEASURING
CHANGES IN THE
SYSTEM

44. Evaluating transects
• Same time of day (abiotic and
biotic variables)
• Samples taken througout the year
(seasonal variations)
• Repeat transects for reliable data
(minimum 3 times)
• Random number generator for
where to take transects to
eliminate bias

45. Measuring changes – human
activity
• Satellite images
eg. deforestation
• Monitoring stations
eg. Taiwan EPA
• Erosion rates

46. Environmental Impact
Assessments (EIAs)
• To decide if the project will be too
damaging or not, and to mitigate any
damage.
1. Baseline study
2. Monitoring during and after
development

47. Variables in EIA
• Habitat type and abundance
• Species list and diversity including
endangered species
• Land use – access and coverage
• Water flow
• Human population
• Soil quality and fertility
• Example EIA for a dam project