1 Lipids Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings.
Communities and Ecosystems. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin...
-
Upload
alberto-wickware -
Category
Documents
-
view
213 -
download
0
Transcript of Communities and Ecosystems. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin...
Communities and EcosystemsCommunities and Ecosystems
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Trophic structure is a key factor in community dynamics
•Every community has a trophic structure
–A pattern of feeding relationships consisting of several different levels
–The sequence of food transfer from producer to consumer is called a food chain.
•Producers are autotrophs (“self feed”)
•Consumers are heterotrophs (“different feed”)
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Food chains interconnect, forming food webs
• A food web
–A network of interconnecting food chains
–Arrows indicate direction of nutrient transfer
–Several 1° Consumers depend on same producer
–Some eat at multiple levels
Figure 37.10
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Ecosystem ecology emphasizes the processes
energy flow and chemical cycling
Chemicalcycling
Energyflow
Lightenergy
Chemicalenergy
Chemical elements
Heatenergy
Figure 37.11
An ecosystemIncludes a community and the abiotic factors with which it interacts.
Transfer substances through trophic levels. But one flows out the other cycles within.
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Each day Earth receives energy from the sun equivalent to 100 million atomic bombs…
Most is absorbed, scattered, and reflected by our atmosphere or by the Earths surface.
Only 1% of all the light energy the Earth receives is converted into chemical energy by primary producers through photosynthesis (the process of changing light into sugar and other foods/chemical energy).
However, on a global scale this is enough to produce170 billion tons of organic material per year.
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
The amount of living organic material in an ecosystem is its Biomass.
The amount of solar energy converted to chemical energy (organic material) by producers in a given area at a given time is called primary production.
Primary production
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Primary production sets the energy budget for ecosystems
• Is the rate at which producers convert sunlight to chemical energy in organic matter (biomass)
Open ocean
Estuary
Algal beds and coral reefs
Tundra
Temperate grassland
Cultivated land
Boreal forest (taiga)
Savanna
Temperate deciduous forest
Tropical rain forest
0 500 1,000 1,500 2,000 2,500
Average net primary productivity (g/m2/yr)Figure 37.12
Desert and semidesert scrubContributes most to Earth’s total net production due to its size
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Energy supply limits the length of food chains
• A pyramid of production
– Shows the flow of energy from producers to primary consumers and to higher trophic levels
Tertiaryconsumers
Secondaryconsumers
Primaryconsumers
Producers
10 kcal
100 kcal
1,000 kcal
10,000 kcal
1,000,000 kcal of sunlight
Figure 37.13
Can’t eat all
Can’t digest all
2/3 digested used by cells
Rest to mass (growth)
Only this can be eaten by next
level.
1/1000 of the sun’s energy makes it this far
(1% of sun’s energy)
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Only about 10% of the energy stored at each trophic level is available to the next level
• Only a tiny amount of the energy converted by primary producers flows through he food chain to the top consumer
• This is why top level consumers require so much territory…
– It takes a lot of vegetation to support trophic levels so many steps removed from photosynthetic production.
• Also why food chains are limited in size
– Limited by availability of energy
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
A production pyramid explains why meat is a luxury for humans
• A field of corn
– Can support many more human vegetarians than meat-eaters (less energy is wasted)
CONNECTION
Trophic level
Secondaryconsumers
Primaryconsumers
Producers
Humanvegetarians
Corn
Humanmeat-eaters
Cattle
Corn
Figure 37.14
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Consumers
Producers
Nutrientsavailable
to producers
Abioticreservoir
Detritivores
3
2
1
4
Chemicals are recycled between organic matter (organisms) and abiotic reservoirs
Biogeochemical cycle
Figure 37.15
Soil
Decomposers
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Water moves through the biosphere in a global cycle
Figure 37.16
Transportover land
Solar energy
Net movement ofwater vapor by wind
Runoff andgroundwater
Percolationthroughsoil
Precipitationover landEvaporation and
transpiration fromland
Precipitationover ocean Evaporation
from ocean
Solar heatdrives the global water cycle through
precipitation, evaporation, and transpiration
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Human activity affects the global water cycle
1)Important source of atmospheric water is transpiration, so destruction of the rain forests will change amount of water in the atmosphere and can alter local and global weather patterns.
2) Pumping large amounts of ground water to the surface for irrigation can increase evaporation and deplete ground water supplies.
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
The carbon cycle relies on photosynthesis, respiration, and decomposition
Carbon compounds (organic) are consumed.
Respiration returns CO2 to the atmosphere.
Photosynthesis = Respiration
Burning fossil fuels is increasing CO2 levels and is causing global warming.
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
The nitrogen cycle relies heavily on bacteria
Figure 37.18
Nitrogen is a constituent of DNA and proteins…is essential for life.
Various bacteria in soil convert gaseous N2 to compounds that plants use:
ammonium (NH4+) and nitrate (NO3–)
Detritivores decompose organic matter and recycle nitrogen to plants.
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Humans are altering the nitrogen cycle
1)Sewage treatment facilities often empty large amounts of nitrogen into rivers and streams
2) Fertilizer is routinely applied
• These nitrogen sources continue to fertilize when they enter lakes and streams causing algae blooms
• Nitrates enter ground water used as drinking water and can be toxic
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
The phosphorus cycle depends on rock weathering
Figure 37.19
Phosphorus is needed for nucleic acids (DNA), phospholipids (cell membranes), bones and ATP (energy)
It and other soil minerals are recycled locally.
Weathering is a slow process so phosphorus is limited.
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
In aquatic systems that have not been altered by humans the limited amount of phosphorus keeps algae to a minimum.
In areas affected by humans (sewage, fertilizers, pesticides) phosphate pollution leads to heavy algal growth.
Major algae blooms can kill aquatic organisms and be toxic to humans.