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