Ecosystems

1
Ecosystems

• Chapter 54

2

• Ecosystem involves all abiotic and biotic factors
  in area.
• Trophic levels - groups in which organisms are
  placed according to eating patterns.
• Ecosystems - involve nutrient cycles.

3
http//www.oahunaturetours.com/pelagic/images/sbbf
oodchain1.GIF
4

• Autotrophs - self-feeders (usually
  photosynthesize) -primary producers
• They use light to make sugars, other chemicals
  necessary for life.

5
http//static.howstuffworks.com/gif/irrigation-pho
tosynthesis.gif
6

• Heterotrophs - rely on organisms for food.
• Herbivores eat primary producers (primary
  consumers)
• Carnivores - eat primary consumers (secondary
  consumers)
• Tertiary consumers - eat secondary consumers.

7
(No Transcript)
8

• Detritivores - decomposers - break down detritus
  (dead organic matter left after organism dies)
• Organic matter must be recycled in ecosystem.
• Biggest decomposers - fungi and prokaryotes
  (secrete enzymes to break down dead material)

9
(No Transcript)
10

• Primary production - amount of light that can be
  converted to energy in a given time.
• All contributes to energy budget in an area
  (determines how much energy available to
  ecosystem)

11
http//adaptation.nrcan.gc.ca/posters/images/pr_02
_01_e.gif
12

• Gross primary productivity - amount of light
  energy converted to chemical energy.
• Net primary productivity - gross productivity
  minus amount of energy used by primary producers
  for respiration (amount of energy left over)

13
http//eostc.umt.edu/forestry/Products/Production/
Forest20Production/first_modis_gpp.gif
14

• Primary production - expressed in terms of
  biomass (amount of vegetation added to ecosystem
  per unit area per unit time)
• Each ecosystem different amount of biomass.

15
(No Transcript)
16

• Oceans - amount of light to hit ocean floor
  contributes biomass.
• Light can only go to certain level primary
  productivity of area may be lower in deeper
  oceans.

17
(No Transcript)
18
Primary Productivity Map
19

• Nutrients also contribute to biomass in aquatic
  areas.
• Nitrogen - plant growth (can be limited in water)
• Water pollution adds nutrients to water
  (eutrophication)
• Shifts organisms living in water and is a
  negative impact of humans.

20
Eutrophication of lake
21

• Land areas - temperature and water availability
  also determines primary productivity.
• Minerals in soil can affect production as well.

22
http//www.usf.uni-osnabrueck.de/hlieth/npp/npp.g
if
23

• Efficiency between trophic levels is about 20.
• Transfer from one level to next is only 20 of
  energy from level before.

24
(No Transcript)
25

• Biomass pyramids show transformations between
  trophic levels.
• Differ dramatically between ecosystems.

26
(No Transcript)
27
(No Transcript)
28

• Nutrient cycling involves abiotic and biotic
  factors (biogeochemical cycling)
• Water cycling physical cycle and not chemical
  not considered biogeochemical cycle, but still
  essential to ecosystem.

29
(No Transcript)
30
Carbon cycle is a biogeochemical cycle.
31

• Nitrogen enters an ecosystem in 2 ways.
• Added to soil in usable form.
• Can also enter through nitrogen fixation -
  prokaryotes convert nitrogen into usable organic
  compounds like amino acids.

32
(No Transcript)
33

• Product of nitrogen fixation is ammonia.
• Ammonia picks up H in soil to become ammonium
  (ammonification)
• Plants can use this nitrogen.
• Aerobic bacteria can turn ammonium into a nitrate
  (nitrification)

34
http//www.thisland.uiuc.edu/50ways/images/5b.jpg
35

• Nitrates - used by plants.
• In final step, other bacteria use oxygen from
  nitrates and release N2 back into atmosphere
  (denitrification)

36
http//generalhorticulture.tamu.edu/lectsupl/Nutri
ent/p79f1.gif
37

• Phosphorus occurs only in phosphate - plants
  absorb and use to make organic nutrients.
• Does not come from atmosphere.
• Recycling of phosphorus is usually confined to
  specific areas.

38
(No Transcript)
39

• Rate of decomposition determines rate of chemical
  cycling.
• Tundra - decomposition can take years rain
  forest - decomposition takes much less time.

40
http//farm1.static.flickr.com/221/507417180_dfd8f
5e8ac.jpg?v0
41

• Humans affect rate of chemical cycling due to
  habits.
• Farmers - disturb crop areas by removing
  nutrients in soil.
• Humans - add fertilizers to soil which disrupt
  chemical balances.
• Chemicals can enter water, disrupting animals
  that live there.

42
(No Transcript)
43

• Burning of fossil fuels - major contributors to
  nutrients in atmosphere.
• Sulfur and nitrogen placed into atmosphere
  change into acid precipitation.

44
Acid precipitation
45

• Acid precipitation can alter pH of soil and alter
  the vegetation that lives there.

46
(No Transcript)
47

• Poisonous materials also added to our soils and
  water.
• Further up food chain, more organism is affected
  by chemicals.
• DDT (a pesticide) damaged birds and fish when it
  met with water.

48
(No Transcript)
49

• Amount of carbon dioxide in atmosphere has been
  rising for decades.
• Carbon dioxide helps to keep in heat that would
  normally escape atmosphere (greenhouse effect)

50
(No Transcript)
51

• Ozone layer is thinning as a result of fossil
  fuels.
• Ozone protects humans from UV rays.

52
(No Transcript)