Modules 36 Komunitas

7/28/2019 Modules 36 Komunitas

1/45

Copyright 2003 Pearson Education, Inc. publishing as Benjamin Cummings

All the organisms in a particular area make upa community

A number of factors characterize everycommunity

Biodiversity

The prevalent form ofvegetation

Response to disturbances

Trophic structure(feeding relationships)

36.1 A community is all the organisms inhabiting aparticular area

Figure 36.1


2/45


Biodiversity is the variety of different kinds oforganisms that make up a community

Biodiversity has two components

Species richness, or the total number of

different species in the community

The relative abundance of different species


3/45


Interspecific competition occursbetween twopopulations if they both require the same

limited resource

A population's niche is its role in thecommunity

The sum total of its use of the biotic and abioticresources of its habitat

36.2 Competition may occur when a sharedresource is limited

STRUCTURAL FEATURES OF COMMUNITIES


4/45


Predation is an interaction where one specieseats another

The consumer is called the predator and the

food species is known as the prey

Parasitism can be considered a form ofpredation

36.3 Predation leads to diverse adaptations in bothpredator and prey


5/45


As predators adapt to prey, sometimes naturalselection also shapes the prey's defenses

This process ofreciprocaladaptation is

known ascoevolution

Example:

Heliconius andthe passionflowervine

Figure 36.3A

Eggs

Sugardeposits


6/45


Prey gain protection against predators througha variety of defense mechanisms

Mechanical defenses, such as the quills of aporcupine


7/45Copyright 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Chemical defenses are widespread and veryeffective

Animals with effective chemical defenses areoften brightly colored to warn predators

Example: the poison-arrow frog

Figure 36.3B



Camouflage is a very common defense in theanimal kingdom

Example: the gray tree frog

Figure 36.3C



A keystone species exerts strong control oncommunity structure because of its ecologicalrole

A keystone predator may maintain communitydiversity by reducingthe numbers of thestrongest competitors

in a communityThis sea star is a

keystone predator

36.4 Predation can maintain diversity in acommunity

Figure 36.4A



Predation by killer whaleson sea otters, allowing sea

urchins to overgraze on kelp

Sea otters represent thekeystone species

Figure 36.4B



A symbiotic relationship is an interactionbetween two or more species that live togetherin direct contact

There are three main types of symbioticrelationships within communities

Parasitism

Commensalism

Mutualism

36.5 Symbiotic relationships help structurecommunities



Parasitism is a kind of predator-preyrelationship

The parasite benefits and the host is harmed inthis symbiotic relationship

A parasite obtains food at the expense of its host

Parasites are typically smaller than their hosts



In the 1940s, Australia was overrun byhundreds of millions of European rabbits

The rabbits destroyed huge expanses of Australia

They threatened the sheep and cattle industries

In 1950, a parasitethat infects rabbits(myxoma virus)

was deliberatelyintroduced tocontrol the rabbitpopulation

Figure 36.5A


14/45


Commensalism is a symbiotic relationshipwhere one partner benefits and the other is

unaffected

Examples of commensalism

Algae that grow on the shells of sea turtles

Barnacles that attach to whales

Birds that feed on insects flushed out of thegrass by grazing cattle


15/45


A community interacts with abiotic factors,forming an ecosystem

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

Chemicals are recycled between air, water,soil, and organisms

36.8 Energy flow and chemical cycling are the twofundamental processes in ecosystems

ECOSYSTEM STRUCTURE AND DYNAMICS


16/45


A terrarium ecosystem

Figure 36.8

Chemical cycling(C, N, etc.)

Lightenergy

Chemicalenergy

Heatenergy


17/45


A food chain is the stepwise flow of energy andnutrients

from plants (producers)

to herbivores (primary consumers)

to carnivores (secondary and higher-levelconsumers)

36.9 Trophic structure is a key factor in ecosystemdynamics


18/45


Figure 36.9A

TROPHIC LEVEL

Quaternaryconsumers

Tertiaryconsumers

CarnivoreCarnivore

Carnivore Carnivore

Carnivore Carnivore

Herbivore Zooplankton

Plant Phytoplankton

Secondary

consumers

Primaryconsumers

Producers

A TERRESTRIAL FOOD CHAIN AN AQUATIC FOOD CHAIN


19/45


Decomposition is the breakdown of organiccompounds into inorganic compounds

Decomposition is essential for the continuationof life on Earth

Detritivoresdecompose wastematter and recyclenutrients

Examples: animalscavengers, fungi,and prokaryotes

Figure 36.9B


20/45


A food web is a network of interconnectingfood chains

It is a more realistic view of the trophicstructure of an ecosystem than a food chain

36.10 Food chains interconnect, forming food webs


21/45


Figure 36.10

Tertiaryandsecondaryconsumers

Secondaryandprimaryconsumers

Primaryconsumers

Producers

(Plants, algae,phytoplankton)

Detritivores

(Prokaryotes, fungi,certain animals)

Wastes anddead organisms


22/45


Biomass is the amount of living organicmaterial in an ecosystem

Primary production is the rate at which

producers convert sunlight to chemical energy

The primary production of the entire biosphereis about 170 billion tons of biomass per year

36.11 Energy supply limits the length of food chains


23/45


A pyramid of production reveals the flow ofenergy from producers to primary consumers

and 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


24/45


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

level

This stepwise energy loss limits most foodchains to 3 - 5 levels

There is simply not enough energy at the verytop of an ecological pyramid to support anothertrophic level

36 12 C i A i i i


25/45


The dynamics of energy flow apply to thehuman population as much as to otherorganisms

When we eat grain or fruit, we are primaryconsumers

When we eat beef or other meat from herbivores,we are secondary consumers

When we eat fish like trout or salmon (which eatinsects and other small animals), we are tertiaryor quaternary consumers

36.12 Connection: A production pyramid explainswhy meat is a luxury for humans


26/45


Because the production pyramid tapers sosharply, 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

36 13 Ch i l l d b t i


27/45


Ecosystems require daily infusions of energy

The sun supplies the Earth with energy

But there are no extraterrestrial sources ofwater or other chemical nutrients

Nutrients must be recycled between organismsand abiotic reservoirs

Abiotic reservoirs are parts of the ecosystemwhere a chemical accumulates

36.13 Chemicals are recycled between organicmatter and abiotic reservoirs


28/45


There are four main abiotic reservoirs

Water cycleCarbon cycle

Nitrogen cycle

Phosphorus cycle

35 14 W t th h th bi h i


29/45


Heat from the sun drives the global water cycle

Precipitation

Evaporation

Transpiration

35.14 Water moves through the biosphere in aglobal cycle


30/45


Figure 36.14

Solarheat

Precipitationover the sea

(283)

Net movement

of 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

36 15 Th b l d d h t th i


31/45


Carbon is taken from the atmosphere byphotosynthesis

It is used to make organic molecules

It is returned to the atmosphere by cellularrespiration

36.15 The carbon cycle depends on photosynthesisand respiration


32/45


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

36 16 Th it l li h il b t i


33/45


Nitrogen is plentiful in the atmosphere as N2

But plants cannot use N2

Various bacteria in soil (and legume rootnodules) convert N2 to nitrogen compoundsthat plants can use

Ammonium (NH4

+) and nitrate (NO3

)

36.16 The nitrogen cycle relies heavily on bacteria


34/45


Some bacteria break down organic matter andrecycle nitrogen as ammonium or nitrate to

plants

Other bacteria return N2 to the atmosphere


35/45


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

36 17 The phosphorus cycle depends on the


36/45


Phosphates (compounds containing PO43-

) andother minerals are added to the soil by thegradual weathering of rock

Consumers obtain phosphorus in organic formfrom plants

Phosphates are returned to the soil through

excretion by animals and the actions ofdecomposers

36.17 The phosphorus cycle depends on theweathering of rock


37/45


Figure 36.17

Upliftingof rock

Phosphatesin solution

Weatheringof rock

Phosphates

in rock

Phosphatesin organic

compounds

Detritus

Detritivoresin soil

Phosphatesin soil(inorganic)

Rock Precipitated(solid) phosphates

Plants

Animals

Decomposition

Runoff


38/45


39/45


Dams were builtacross streams at

the bottom of eachwatershed tomonitor water andnutrient losses

Figure 36.18A


40/45


In 1966, one of the valleys was completelylogged

It was thensprayed withherbicides for3 years to

prevent plantregrowth

All the original

plant materialwas left inplace todecompose Figure 36.18B


41/45

36 19 Talking About Science: David Schindler


42/45


Eutrophication is a process in which nutrientrunoff from agricultural lands or livestockoperations causes photosynthetic organisms in

ponds and lakes to multiply rapidly

The result is algal bloom

36.19 Talking About Science: David Schindlertalks about the effects of nutrients onfreshwater ecosystems


43/45


Algal bloom can cause a pond or lake to losemuch of its species diversity

Human-caused eutrophication wiped outfisheries in Lake Erie in the 1950s and 1960s

Figure 36.19B


44/45


Dr. David Schindler is an ecologist who workedat the Experimental Lakes Project in northern

Ontario

He performedseveral classic

experiments oneutrophicationthat led to the banon phosphates in

detergents

Figure 36.19A


45/45

According to Dr. Schindler, there are threeserious threats to freshwater ecosystems

Acid precipitation

Climate warming

Changes in land use

Documents

Modules 36 Komunitas