Download - Ecosystems
Chapter 47
Table 1Period 4
Ecosystems
Ecosystem
An association of
organisms and their
physical environment,
interconnected by
ongoing flow of energy
and a cycling of
materials (open system)
Simple Ecosystem ModelEcosystems include deserts,
hardwood forests, tundra, prairies, reefs, oceans, streams, lakes, ect.
These ecosystems run on energy that autotrophs produce by photosynthesis. Ex. Plants and
PhytoplanktonThey are called primary
producers.Every other organism is called
a consumer or heterotrophs.
Consumers
Herbivores - have a strict diet of only plants…(Red fox)Carnivores - have a strict diet of only flesh…(Crocodiles)Parasites - live in or on their host and feed on its tissue…
(Fleas)Scavengers - feeds on dead and decaying animals…
(vultures) Detritivores such as earthworms and crabs feed on detritus
(decomposing organic matter).Decomposers break down organic remains and wastes of
other living organisms.Omnivores - feed on plants, animals and microbes .
Omnivores consume two or more types of organisms.
Trophic Levels
Trophic level - the level on the food chain on which an organism is.
Food chain - Linear sequence of steps by which energy stored in autotroph tissues enters higher trophic levels.
Food Websa community of organisms
where there are several interconnected food chains.
Chapter 47
Two Types of Food Webs
Producers (photosynthesizers)
Energy Input: Energy Input:
herbivores
carnivores
decomposers
decomposers
detritivores
Energy Output
Energy Output
energy lossesas metabolic heat & as net export from ecosystem
Producers (photosynthesizers)
decomposers
detritivores
Transfers: Transfers:
energy in organic wastes, remains
Grazing Food Web
Detrital Food Web
Producers (Photosynthesizers) Producers (Photosynthesizers)
Herbivores
Carnivores
Decomposers
Decomposers
Detritivores
Pesticides
Many plants have natural toxins that repel herbivores, but do not harm them. We do not get sick or die from the toxins because toxicity is a function of concentration.
In 1945, scientists started to make synthetic toxins & to identify mechanisms by which toxins attack pests. herbicides- kill weeds by disrupting
metabolism & growth. insecticides- clogs airways of target
insects, disrupts its nerves & muscles, or prevent its reproduction.
fungicides- works against harmful fungi.
DDT
It takes two to fifteen years for this nerve cell poison to break down.
Insoluble to water.Can easily disperse in vapor form. Highly soluble in fats, so can accumulate in tissues of
consumer's organs.Can show biological magnification – the ever increasing
concentration of a slowly degradable or nondegradable substance in body tissues as it is passed along in food chains
DDT
Disrupts metabolic activities & are toxic to many aquatic and terrestrial animals.
No one predicted the effects of DDT, it was incriminally killing the natural predators that keep pests in check.
Effects started to show up in habitats far removed from DDT and much later in time.
Most Vulnerable Victims
•Brown pelicans
•Bald eagles
•Peregrine falcons
•Other top carnivores
DDT
DDT breakdown interferes with some physiological processes.
Some birds still lay thin-shelled eggs since the ban in the 1970s.
DDT from industrial waste discharges that had stopped twenty years earlier still contaminate ecosystems today.
Energy Flow Through Ecosystems
primary productivity- the rate at which producers capture & store energy in their tissues during a given interval.
How much energy stored depends on: amount of producers. balance between photosynthesis & aerobic energy (balance
between energy trapped & energy used). gross primary production- energy initially trapped by
producers. net primary production- fraction of trapped energy that
producers funnel into growth & reproduction.net ecosystem production- the gross primary production minus
the energy used by producers & soil decomposersFactors that impact net production:
seasonal patterns distribution through habit
Biomass Pyramid
• Depicts the dry weight of all of an ecosystem's organisms at each tier.
Energy Pyramid Model
Illustrates how the amount of usable energy diminishes as it is transferred through an ecosystem.
Energy transfers are never 100 percent efficient. Some energy is lost as heat. Some biomass is not digested.
Some energy is lost at each step.Limits the number of trophic levels in an ecosystem .
21
383
3,368
20,810 kilocalories/square meter/year
top carnivores
carnivores
herbivores
producers
decomposers + detritivores = 5,080
Biogeochemical Cycles
An essential element moves from the environment, through ecosystems, then back to the environment.
No other element can directly or indirectly fulfill the metabolic role of such elements, or nutrients, which is why we call them essential. Ex. oxygen, hydrogen, carbon, nitrogen, and phosphorus.
Nutrients move into and out of ecosystems by way of natural geologic processes.
Decomposers help cycle the nutrients in ecosystems.
Biogeochemical Cycles
There are three types of biogeochemical cycles. Portions of the environment are reservoirs for specific elements. Hydrologic cycle – oxygen and hydrogen move on a grand
scale, in molecules of water. Atmospheric cycles – some gaseous form of the nutrient is
the one available to ecosystems. Include the Carbon Cycle and the Nitrogen Cycle.
Sedimentary cycles – Phosphorus and other solid nutrients accumulate on the seafloor and eventually return to land through geological uplifting, which usually takes millions of years.
biogeochemical cycleMain nutrient reservoirs in the
environment
fraction of nutrient
available to ecosystem
primary producers
herbivores, carnivores, parasites
detritivores, decomposers
Environmental ReservoirsPortions of the
environment are reservoirs for specific elements.
The Water Cycle
The hydrologic cycle.Water slowly moves on a global scale from the
world ocean – the main reservoir – through the atmosphere, onto land, then back to the ocean.
Water moves nutrients into and out of ecosystems.A watershed is any region where precipitation flows
into a single stream or river.Ecologists measure nutrient
inputs and outputs in forests
through watersheds.
Main Reservoirs
Volume (103 cubic kilometers)
1,370,00029,000
4,000230
6714
OceansPolar ice, glaciersGroundwaterLakes, riversSoil moistureAtmosphere (water vapor)
Overview of Hydrologic Cycle
Atmosphere
Ocean Land
evaporation from ocean
425,000
precipitation into ocean
385,000
evaporation from land plants (evapotranspiration)
71,000
precipitation onto land 111,000
wind-driven water vapor40,000
surface and groundwater flow 40,000
Figure 47-15Page 853
EVAPORATION PRECIPITATION TRANSPIRATION
dripping, tricklingdown along stems
falling throughto ground
interception by plants
surface pooling, etc.
infiltration of soil
moisture in soil
seepage, percolation
groundwater storage
DEEP OUTFLOW
overland flow
lateral flow
base flow
STREAM OUTFLOW
Fig. 47-16, p.853
Groundwater
Soil and aquifers hold groundwater.Chemicals from landfills, hazardous waste dumps
and underground tanks are contaminating it.Polluted groundwater is difficult and expensive to
clean up.
Groundwater Overdraft and Pollution
Salinization and Desalinization
Two-thirds of fresh water that humans use goes to irrigating fields.
Piped-in water commonly has high concentrations of mineral salts.
Evaporation results in salinization, or a buildup of salt in soil. stunts crop plants decreases yields.
Desalinization is removing the salt from seawater through distillation or pushing water through membranes. Requires fossil fuels. Very costly.
The Carbon Cycle
Carbon moves through the lower atmosphere and all food webs on its way to and from its large reservoirs.
Carbon reservoirs: Earth’s crust holds the vast majority of carbon. The Ocean is the next largest reservoir. Most of the annual cycling of carbon occurs between the
ocean and the atmosphere.
Carbon moves into and out of ecosystems mainly when combined with oxygen. Ex. Carbon dioxide, bicarbonate, and carbonate.
Carbon Cycle - Marine diffusion between atmosphere and ocean
bicarbonate and carbonate in ocean water
marine food webs
marine sediments
combustion of fossil fuels
death, sedimentation uplifting
sedimentation
photosynthesis aerobic respiration
incorporation into sediments
Carbon Cycle - Land
photosynthesis aerobic respirationterrestrial
rocks
soil water
land food webs
atmosphere
peat, fossil fuels
combustion of wood
sedimentation
volcanic action
death, burial, compaction over geologic time
leaching, runoff
weathering
combustion of fossil fuels
Carbon in the Ocean
The ocean holds 38,000-40,000 gigatons of dissolved carbon.Ocean currents carry carbon primarily in the form of bicarbonate
and carbonate ions.
Carbon in the Atmosphere
Atmospheric CycleAtmospheric carbon is mainly carbon dioxide
Added by aerobic respiration, volcanic action, burning fossil fuels Removed by photosynthesis
Carbon is a greenhouse gas.Greenhouse gases impede the escape of heat from Earth’s surface and make life on earth possible.
The greenhouse effect - As heat builds up in the lower atmosphere, the Earth’s temperature rises.
Global Warming
1. Wavelengths in rays from the sun penetrate the lower atmosphere and warm the earth’s surface.
Global Warming
2. - The surface radiates heat (infrared wavelengths) to the atmosphere where some of it escapes to space.
- Greenhouse gasses and water vapor trap infrared energy and radiate a portion of it back toward the Earth.
Global Warming
3. - Increased concentrations of greenhouse gasses trap more heat near the earth’s surface and more water vapor evaporates into the atmosphere.
- Results in global warming - a long term increase in temperature near Earth’s surface.
Global Warming
Long term increase in Earth’s lower atmosphere over time.
Nitrogen Cycle
Atmospheric cycleNitrogen moves from its largest reservoir (the
atmosphere), through the ocean, ocean sediments, soils, and food webs, then back into the atmosphere.
Nitrogen is used in amino acids and nucleic acids.
Nitrogen fixation
Starts the Nitrogen Cycle.Plants cannot use nitrogen gas.Bacteria attached to the roots
of plants convent gaseous nitrogen (N2) to ammonia (NH3).
The ammonia is then converted to ammonium (NH4
+) and nitrate (NO3
-).
Most plants easily take up these two forms of nitrogen.
Other processes affecting the Nitrogen Cycle
Ammonification – soil fungi and bacteria decompose nitrogen-containing compounds ammonia and ammonium.
Nitrification – bacteria convert ammonia and ammonium to nitrite and nitrate, which plants can absorb.
Denitification - conversion of nitrate and nitrite to gaseous nitrogen (N2) or nitrogen oxide (NO2) certain soil bacteria.
gaseous nitrogen (N2) in atmosphere
NO3-
in soil
nitrogen fixationby industry
fertilizers
NH3-,NH4
+
in soil
1. Nitrification leaching
uptake by autotrophs
excretion, death, decomposition
uptake by autotrophs
nitrogen fixation
leaching
ammonification 2. Nitrification
dentrification nitrogenous
wastes, remains
NO2-
in soil
food webs on land
Overview of Nitrogen Cycle
Phosphorus Cycle
A sedimentary cycle.Phosphorus (mainly phosphate) moves from land, through
food webs, to ocean sediments, then back to land.Earth’s crust is the largest reservoir of phosphorus.Occurs over millions of years.
Weathering and erosion deliver phosphate ions to streams and rivers.
Rivers take them to the sea. The ions accumulate and for insoluble deposits on submerged
continental shelves. After millions of years, crustal movements may uplift parts of the
seafloor and expose the phosphate on land surfaces.
Flow of Phosphates through Food Chains
Phosphates are required to form ATP.
1. Plants take up dissolved phosphates from soil water.
2. Herbivores obtain phosphate from eating plants.
3. Carnivores obtain phosphate from eating herbivores.
4. Animals lose phosphate in urine and waste.
5. Decomposers release phosphate from organic wastes and remains.
6. Plants take the phosphates up again.
Overview of Phosphorus Cycle
guano
fertilizer
terrestrial rocks
land food webs
dissolved in seawater
marine food webs
marine sediments
excretion
weathering
mining
agricultureuptake by producers
death, decomposition
sedimentation settling out
leaching, runoff
weatheringuplifting over geologic time
dissolved in soil water,
lakes, rivers
uptake by autotrophs
death, decomposition