1. Ecosystems
Chapter 20
Part A

2. The Nature of Ecosystems
Ecosystems are an association of communities and their physical environment interconnected by an ongoing flow of energy and a cycling of nutrients

3. One-way flow of energy
Cycling of nutrients

4. The Nature of Ecosystems
Ecosystems are open systems because they require ongoing inputs of energy
There is a one-way flow of energy through ecosystems
Sun  producers  consumers  decomposers
Some energy escapes as heat
Energy for living organisms is continually resupplied from the sun

5. The Nature of Ecosystems
Primary producers (autotrophs)
Photoautotrophs capture and convert the sun’s energy to chemical bond energy
Build glucose and other compounds
Plants, algae, and photosynthetic bacteria
Chemoautotrophs capture energy from get energy and carbon from deep-sea vents

6. The Nature of Ecosystems
Primary production
The rate that energy is captured and stored
Anything affecting producer growth will impact primary production
Terrestrial production: temperature and moisture
Aquatic production: nutrient availability
Factors can vary
seasonally causing productivity to vary
from ecosystem to ecosystem

7. The Nature of Ecosystems
Consumers
Feed on producers or other consumers
Described by their diet
Herbivore = plants
Carnivore = flesh of animals
Omnivores = plant and animals
Parasites = live in or on and eat their host
Detritovores = bits of decaying organic matter (detritis)
Decomposers = wastes and remains

8. Food Chains and Webs
Pathways showing the transfer of energy and nutrients from organism to organism within an ecosystem
Shows the trophic structure of an ecosystem
Troph means nourishment
Each trophic level represents the number of energy transfers away from the original energy input into that system

10. Food Chains and Webs Trophic Structure First trophic level
Primary producers (autotrophs)
Photosynthesis or chemosynthesis
Second trophic level
Primary consumers (heterotrophs)
Herbivores, omnivores
Third trophic level
Secondary consumers (heterotrophs)
Carnivores (primary level), omnivores
Fourth trophic level
Third level consumers (heterotrophs)
Carnivores (second level)

11. Fig

12. Figure 42.5 Computer model for a land food web in East River Valley, Colorado. Balls signify species. Their colors identify trophic levels, with producers (coded red) at the bottom and top predators ( yellow) at top. The connecting lines thicken, as they go from an eaten species to the eater.
Fig. 42.5, p. 713

13. Food Chains and Webs Trophic Structure
The number of trophic levels is limited based on the efficiency of energy transfers
Only 5-30% of the energy in one level ends up in the next level
Some energy is used to reproduce
Some energy escapes as metabolic heat
Some energy is bound up in body parts that can’t be digested (bone, lignin, hair, etc)

15. Ecological Pyramids
Depict the distribution of materials and energy between trophic levels

16. top carnivores (gar and bass) 1.511
carnivores (smaller
fishes, invertebrates) 37
herbivores
(plant-eating fishes,
invertebrates, turtles)
detritivores
(crayfish) and
decomposers
(bacteria) 5
Biomass pyramid (grams per square meter)
809
producers (algae
and aquatic plants)
Figure 42.6 Ecological pyramids for Silver Springs, an aquatic ecosystem in Florida.
Stepped Art
Fig. 42.6a, p. 713

17. detritivores + decomposers = 5,060 carnivores 38321
top carnivores
detritivores + decomposers = 5,060
carnivores
383
3,368
herbivores
20,810
producers
Energy flow pyramid (kilocalories per square meter per year)
Figure 42.6 Ecological pyramids for Silver Springs, an aquatic ecosystem in Florida.
Stepped Art
Fig. 42.6b, p. 713

18. Answer the questions based on the figure
What trophic level is the sparrow?
What consumer level is the coyote?
Approximately what percentage of energy does the grasshopper get from the grass?
Which organism is an herbivore?
If the coyote also eats the grasshopper would that make it an omnivore?
If insecticide was sprayed reducing the number of grasshoppers what would that do to the number of coyotes? To the amount of grass?

19. Biogeochemical Cycles
Elements essential for life move between a community and the environment
Cycle from environmental reservoirs, through organisms, and then back to the reservoirs

20. Biogeochemical Cycles
Water
Needed for all cellular fluids
Required for photosynthesis

21. Biogeochemical Cycles
Water
Found as vapor in the atmosphere (atmospheric cycle)
Condenses into droplets causing rain
Rain water
seeps into the ground (and is tapped by plant roots)
Drains into aquifers
Runs off into rivers, lakes, and the ocean
Soil water which is tapped by roots
Evaporation due to solar energy returns the water to atmospheric vapor

22. Precipitation into ocean
Atmosphere
Precipitation
onto the land
Windborne water vapor
Evaporation from ocean
Evaporation
from land plants
(transporation)
Precipitation into ocean
Surface and
groundwater
flow
Figure The water cycle. Water moves from the ocean to the atmosphere, land, and back. The arrows identify processes that move water.
Land
Ocean
Stepped Art
Fig. 42.8, p. 715

23. Biogeochemical Cycles
Water
Conservation Concerns
Limited amounts of fresh water
Using aquifer water faster than it accumulates
Contaminated water sources

24. Biogeochemical Cycles
Carbon
Essential part of all organic molecules

25. Biogeochemical Cycles
Carbon
Found in the atmosphere (atmospheric cycle)
Carbon enters terrestrial food webs when plants take up CO2 from the air for use in photosynthesis to make glucose (C6H12O6)
Carbon enters aquatic food webs by dissolving in seawater and being used by aquatic producers
Carbon returns to the air/water as CO2 when organisms carry out aerobic respiration
Burning of fossil fuels also puts carbon in the air

26. death, burial, compaction over millions of years Fossil fuels
burning fossil fuels 6
Land food webs
Atmospheric CO2
photosynthesis 1
aerobic respiration 2
Dissolved carbon
in ocean
diffusion between atmosphere and ocean 3
Marine organisms 4
sedimentation
Earth’s crust 5
Figure The carbon cycle. Most carbon is in Earth’s crust, where it is largely unavailable to living organisms.
Stepped Art
Fig , p. 716

27. Biogeochemical Cycles
Carbon
Conservation Concerns
More CO2 is being released into the atmosphere than is being taken up
Adds to the greenhouse gasses
Group of gasses (CO2, CFC, CH4, and N2O) that act like a pane of glass in a greenhouse
Visible light can pass through
Infrared wavelengths (heat) can’t escape
Help shape global temperatures

28. Greenhouse Effect Sun’s rays Some heat escapes
Increased gasses, less escapes

29. Biogeochemical Cycles
Nitrogen
Essential for amino acids (protein), chlorophyll and hemoglobin

30. Biogeochemical Cycles
Nitrogen
N2 is found in the atmosphere (atmospheric cycle)
Not a useable form for most organisms
Plants and animals can not break the bonds between the two nitrogen atoms

31. Biogeochemical Cycles
Nitrogen
Nitrogen fixation
Certain bacteria can break the bonds of N2 and form ammonia (NH4+)
Nitrogen fixing bacteria live in aquatic habitats, soils, and as mutualistic partners with fungi (lichens) and legumes (form root nodules)

32. Biogeochemical Cycles
Nitrogen
Plants take up NH4 and use it in metabolic reactions
Consumers get nitrogen by eating plants or one another
Nitrogen returns to the soil
Wastes and remains

33. Biogeochemical Cycles
Nitrogen
Denitrification
Some bacteria use nitrogen in energy producing pathways that release N2 into the atmosphere

34. Land food webs denitrification by bacteria Waste and remains6
Waste and remains
decomposition by
bacteria and fungi 3
nitrogen fixation
by bacteria 1
uptake
by producers 2
uptake
by producers 5
Figure Nitrogen cycle in a land ecosystem.
nitrification
by bacteria
Soil nitrates
(NO3–) 4
Soil ammonium
(NH4+)
Stepped Art
Fig , p. 718

35. Biogeochemical Cycles
Nitrogen
Conservation concerns
Not enough nitrogen in the soil and aquatic habitats lowers productivity
Too much nitrogen can run off soils and enter aquatic ecosystems
Causes algal blooms and eutrophication
N2O (nitrous oxide) is a greenhouse gas

36. Biogeochemical Cycles
Phosphorus
Essential for energy (ATP), genetics (DNA, RNA), and structure of living things

37. Biogeochemical Cycles
Phosphorous
Found in rocks and sediments (sedimentary cycle)
Weathering releases phosphorous to soils, lakes, rivers, and ultimately the oceans
Producers take up phosphorous
Consumers obtain phosphorous by eating producers and other consumers
Returns to the soil in wastes and remains

38. uplifting over geologic time Rocks on land
excretion, death,
decomposition
uptake
by producers
Land food webs 5 6
uplifting over geologic time
Rocks
on land 4 1
weathering,
erosion
Phosphates
in seawater
leaching,
runoff 2
Marine
food web 7 8
Phosphates in soil, lakes, rivers
Figure The phosphorus cycle.
Marine sediments 3
Stepped Art
Fig , p. 719

39. Biogeochemical Cycles
Phosphorous
Conservation concerns
Can be a limiting factor for plant growth
Found in fertilizers
Too much phosphorous can run off into aquatic ecosystems
Sources include fertilizer, sewage, detergents
Causes algal blooms and eutrophication

40. Questions Reservoir in rocks and soil
Bacteria are required to “fix” it Water
Impacts global temperatures Carbon
Essential for DNA and RNA Nitrogen
Released by excretion and decomposition Phosphorous
Accumulates in ocean sediments

41. Summary Nature of Ecosystems Food Webs Biogeochemical Cycles
Producers and consumers
Food Webs
Trophic levels
Biogeochemical Cycles
H2O, C, N, P

42. 10% X 10% = 1%
1% X 10% X 10% X 10% = 0.001%
10%
10%
10% 1%
SUN