1

Energy and nutrients

Ecosystem

Energy flows from the sun, through plants, animals, and decomposers, and is lost as heat

Chemicals (nutrients) are recycledbetween air, water, soil, and organisms

A terrarium ecosystem

Figure 36.8

Chemical cycling(C, N, etc.)

Lightenergy

Chemicalenergy

Heatenergy

Presentation adapted from: Campbell, N., Reece, J., Mitchell,L., Taylor,M., 2003. Biology: Concepts and Connections. Powerpoint lectures: Pearson Education, Inc. publishing as Benjamin Cummings

A food chain is the stepwise flow of energy and nutrients

w from plants w to herbivoresw to carnivores

Trophic (food) structure

Figure 36.9A

TROPHIC LEVEL

Quaternaryconsumers

Tertiaryconsumers

Carnivore Carnivore

Carnivore Carnivore

Carnivore Carnivore

Herbivore Zooplankton

Plant Phytoplankton

Secondaryconsumers

Primaryconsumers

Producers

A TERRESTRIAL FOOD CHAIN AN AQUATIC FOOD CHAIN

2

Detritivores decompose waste matter and recycle nutrients

w Examples: animal scavengers, fungi, and bacteria

Figure 36.9B

Decomposition

Food chains interconnect, forming food webs

Figure 36.10

Tertiaryandsecondaryconsumers

Secondaryandprimaryconsumers

Primaryconsumers

Producers

(Plants, algae,phytoplankton)

Detritivores

(Prokaryotes, fungi,certain animals)

Wastes anddead organisms Production pyramid: flow of energy from

producers to higher trophic levels

Figure 36.11

Tertiaryconsumers

Secondaryconsumers

Primaryconsumers

Producers

10 kcal

100 kcal

1,000kcal

10,000 kcal

1,000,000 kcal of sunlight

Only about 10% of the energy in food is stored at each trophic level and available to the next level

The rest is lost as: feces, growth, cellular respiration, & heat loss

Because the production pyramid tapers so sharply, a field of corn or other plant crops can support many more vegetarians than meat-eaters

Figure 36.12

Secondaryconsumers

Primaryconsumers

Producers

Humanvegetarians

Corn

Humanmeat-eaters

Cattle

Corn

TROPHIC LEVEL

3

Ecosystems require daily infusions of energyw The sun supplies the Earth with energyw But there are no extraterrestrial sources of

water or other chemical nutrients

Nutrients must be recycled between organisms and abiotic reservoirsw Abiotic reservoirs are parts of the ecosystem

where a chemical accumulates

Chemicals are recycled between organic matter and abiotic reservoirs There are four main abiotic reservoirs

w Water cyclew Carbon cyclew Nitrogen cyclew Phosphorus cycle

Figure 36.14

Solarheat

Precipitationover the sea(283)

Net movementof water vaporby wind (36)

Flow of waterfrom land to sea(36)

Water vaporover the sea

Oceans

Evaporationfrom the sea(319)

Evaporationandtranspiration(59)

Water vaporover the land

Precipitationover the land(95)

Surface waterand groundwater

Figure 36.15

CO2 in atmosphere

Cellular respiration

Higher-levelconsumers

Primaryconsumers

Plants,algae,

cyanobacteria

Photosynthesis

Wood andfossil fuels

Detritivores(soil microbes

and others) Detritus

Decomposition

Burning

Figure 36.16

Nitrogen (N2) in atmosphere

Amino acidsand proteins in

plants and animalsAssimilationby plants

Denitrifyingbacteria

Nitrates(NO3–)

Nitrifyingbacteria

Detritus

Detritivores

Decomposition

Ammonium (NH4+)

Nitrogenfixation

Nitrogen-fixingbacteria in soil

Nitrogen-fixingbacteria in root

nodules of legumes

Nitrogenfixation

Figure 36.17

Upliftingof rock

Phosphatesin solution

Weatheringof rock

Phosphatesin rock

Phosphatesin organic

compounds

Detritus

Detritivoresin soil

Phosphatesin soil

(inorganic)

Rock Precipitated(solid) phosphates

Plants

Animals

Decomposition

Runoff

4

Nutrient cycling experiment

Dams were built across streams at the bottom of each watershed to monitor water and nutrient losses

Figure 36.18A

In 1966, one of the valleys was completely loggedw It was then

sprayed with herbicides for 3 years to prevent plant regrowth

w All the original plant material was left in place to decompose

Figure 36.18B

Researchers found that the total removal of vegetation can increase the runoff of water and loss of soil nutrients

Figure 36.18C

Environmental changes caused by humans can unbalance nutrient cycling over the long term

w Examplesa) eutrophicationb) acid rain

5

Algal bloom can cause a pond or lake to lose much of its species diversityw Human-caused eutrophication wiped out

fisheries in Lake Erie in the 1950s and 1960s

Figure 36.19B

Dr. David Schindler is an ecologist who worked at the Experimental Lakes Project in northern Ontario

w His experiments on eutrophication led to the ban on phosphates in detergents

Figure 36.19A

According to Dr. Schindler, there are three serious threats to freshwater ecosystems

w Acid precipitationw Climate warmingw Changes in land use

The human alteration of ecosystems threatens the existence of thousands of species

w Zoned reservesa) Undisturbed wildlands surrounded by

buffer zones

Zoned reserves are an attempt to reverse ecosystem disruption

w Costa Rica has established eight zone reserves

Figure 36.20

Guanacaste

Arenal

BajoTempisque

CordilleraVolcanica Central

Pacifico Central

Peninsula de Osa

NICARAGUA

COSTARICA

Caribbean Sea

Llanuras deTortuguero

LaAmistad

PANA

MA

Pacific Ocean

Green: reserves

Yellow: buffers

6

Phyoplankton: March

Phyoplankton: September