Living things are all around us. They are in air, on land and in ...

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4. Environment and Feeding Relationships eLearn.Punjab

• Explaintheecosystem.• Definethetermhabitat.• Comparethedifferentkindsofhabitats.• Investigatethevariousfeaturesthatallowanimalsandplantstoliveinaparticularhabitat.• Identifythefactorsthatcausedailyandyearlychangesinahabitat.• Explainhowlivingthingsadapttodailyandyearlychangesintheirhabitat.• Explainthewaysinwhichlivingthingsrespondtochangesindaily• Environmentalconditionssuchaslightintensity,temperatureandrainfall.• Explainwhyfoodchainsalwaysbeginwithaproducer.• Illustratetherelationshipbetweenproducersandconsumers.• Describetwofoodchainsintheenvironmentaroundthem.• Explainafoodweb.

Living things are all around us. They are in air, on land and in water.

AfterCompletingthischapter,theStudentswillbeableto:

Students’ Learning Outcomes

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Environmentofanorganismconsistsofallthelivingandnon-livingthingsaroundthatorganism.Theselivingandnon-livingthingsaffectthelifeoforganisminonewayortheother.WehavelearntinclassVIthatorganismslivewheretheycanhavetheirneedsmet.Alltheorganismsdependoneachotherandonnon-livingthingsinanenvironment,weshalldiscussitinthischapter.

4.1: Ecosystems

Asystemformedbytheinteractionoflivingorganismsandnon-livingthingsinanenvironmentiscalledanecosystem.Anecosystemmaybelarge,likeadesert,orsmall,likeadecayinglog.Deserts,seashores,rivers,mountains,oceans,grasslandsandrainforestsarealsosomeoftheecosystems.4.1.1: Parts of an Ecosystem

Allecosystemsaremadeoftwoparts:1. Thelivingorbioticpart2. Thenon-livingorabioticpartAlltheplants,animals,fungiandmicroorganismsmakethelivingorbioticpartoftheirecosystem.Organismsofthesamekindlivingandreproducinginaparticularareaiscalledpopulation.Allthepopulationsofdifferentkindsoforganismslivingtogetherinanareamakeacommunity (Fig.4.1).Air,water,soil,sunlightandtemperaturemakethenon-livingorabioticpartofanecosystem.

Fig: 4.1.Thenumberofwolvesinthisforestistheirpopulation.Thewolvesandallotheranimals,plants,microorganismsareincludedinthecommunityoftheforestecosystem.

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4.2: Habitat

Theplacewhereananimalorplantlivesandreproducesiscalleditshabitat.Ahabitatprovidesthethingsanorganismneeds,i.e.food,water,shelter,etc.Manypopulationsoforganismsliveineachhabitat.

Animation 4.2 : Habitat Source and Credit: trrobbin

4.3: Kinds of Habitats

Organismsliveindifferentkindsofhabitats.Anorganismhasspecialfeaturestoliveinitshabitat.

1. The Grassland Habitat

Grassland is agrassy,windy,partly-dryarea. Theseareasreceive amediumamount of rain. The soil foundhere isvery fertile. Grasses are the producers in a grasslandhabitat.Mostlygrazinganimalslikethesheep,goats,cows,antelopes,buffaloes,anddeerareafewexamplesthatarefoundinagrassland.Afewflesh-eaterslikecheetahs,foxes,wolvesandafewbirdslikeowls,eagles,hawks,etc.arealsofoundinthishabitat(Fig.4.2).Manykindsofinsectsarealsofoundingrasslands.

Fig: 4.2.Agrasslandhabitat

2. The Pond Habitat

Apondisanaquatichabitatwhichisrichinlife.Plantslikealgae,duckweed,water lily,etc. are found inwater. Theanimals like fishes, pond skaters, wolf spiders, snails,frogsandmicroscopicorganismsarealsofoundinthepondhabitat(Fig.4.3).

Fig: 4.3. Apondhabitat

http://myweb.usf.edu/~trrobbin/travisresearchpage.html

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3. The Desert HabitatDesertsarethedriestlandareas.Theyreceiveverylittlerainfall.Rainwaterquicklydrainsawayduetothesandysoil. Some plants and animals have adapted to thelimitedsupplyofwater.Cacti,euphorbia,lizards,snakes,kangaroorats,camels,etc.arefoundinadeserthabitat(Fig.4.4).

Fig: 4.4. Adeserthabitat

4. The Rainforest HabitatRainforests are alwayswet. They receive rain thewholeyear.A largenumberofplanttypes (herbs, shrubsandtrees)isfoundhere.Severalvarietiesofbutterflies,snakes,lizards,frogs,parrots,cockatoos,hummingbirds,catsandjaguarsarealsofoundinthishabitat(Fig:4.5).

Fig: 4.5. A rainforest habitat

Extend Your ThinkingExplain,whyalimitedplantandanimallifeisfoundindeserts?

Activity 4.1 Observing a Pond Habitat

Producers Consumers Abioticfactors

• Visitanearbypondunderthesupervisionofyourscienceteacher.

• Observethepondhabitatandfillthetablegivenbelow.

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4.3.1: The Factors Causing Changes in a Habitat

Weknowthatlight,temperature,air,soilandwaterareabioticfactorsoftheenvironment.Changesinthesefactorsbringchangesinthepopulationsofahabitat.Someothernaturalfactorsandhumansalsocausechangesinhabitats.SunlightisthebasicsourceofenergyontheEarth.Plantsuselightenergytomaketheirownfood.AllformsoflifeontheEarthdependdirectlyorindirectlyongreenplantsforfood.Theyalsoneedlightfortheirsurvival(Fig.4.6).Lightintensityaffectsthenumberofplantsinahabitat.Decreaseinnumberofplantsmayresultinthedecreaseofanimals’numberinthehabitat.

Fig: 4.6: Mostplantsandanimalsneedlighttosurvive.

Temperaturecanalsobringchangeinthepopulationofahabitat.Anyextraordinaryriseorfallintemperaturemaydisturbthehabitat.Forexample,warmwatercontainslessoxygen.Whathappenstotheaquaticanimalsinthewaterasitgetshotter?

Waterisessentialforlife.Wherethereismorewater,moreorganismsarefoundthere.Availabilityofwaterinahabitatcangreatlyinfluenceitsorganisms.

Migrationisanotherfactorthatchangesthesizeofpopulationsofahabitat.Whenafewindividualscometoanarea,itincreasesthesizeofthepopulationinthatarea.Organismsmigrateinsearchofbetterlivingplaces.

Extend Your ThinkingHowistheSunimportanttothefoodsupplyofanecosystem?

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Animation 4.3: Indicator of a warming world Source and Credit: myweb

Naturaldisasterssuchasdroughts,floods,earthquakes,etc.canbringchangesinhabitats.Adroughtisaperiodwhenthereisnorainforalongtimeinanarea.Thepondsorstreamsmaydryupduringadrought(Fig.4.7).Mostpondplantsandanimalsdieormovetootherponds.Somecropsdonotgrowintheareaaffectedbyadrought.

Fig: 4.7:Droughtsandfloodsbringrapidchangesinhabitats.

Whenanareagetsalotofrainforalongtime,theremaybea floodinthatarea(Fig.4.7).Manyplantsandanimalsdieormovetootherdrierplacesduringaflood.Sometimeslightningstrikesatreeinaforest,causingforestfires.Plantsandtreesareburnedanddestroyed(Fig.4.8).Someanimalsdie,othersmaymovetosaferplaces.Ittakesmanyyearsforaforesttogrowback.Earthquakes aresuddenshocksof theEarth’s surface.Earthquakescanchangeahabitatveryquickly.OnOctober8,2005,amassiveearthquakedamagedawidespreadareaacrossPakistan.Over70,000peoplelosttheirlives.Alargenumberofanimalsandplantswerealsodestroyed.

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Fig. 4.8: Sometimeslightningdestroysthewholehabitat.

Animation 4.4: DeforestationSource & Credit: Coventryschools Animation 4.5: Deforestation

Source & Credit: Coventryschools

Extend Your ThinkingTwokindsofbirdsliveinthesametree.KindAeatsantsthatliveinthetree.KindBeatsantsandcaterpillars.Whichspeciesismorelikelytosurviveiftheantpopulation

decreases?Why?

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How People Change Habitats

Humanactivitiesalsochangehabitats.Whenhabitatschange,someorganismsdieorleavethehabitat.Farming isvery important tohumansurvival.Peopleclear forests toget land for farming.Peoplealsocutdowntreestogetwoodorpaper.Inthiswaytheydestroythenaturalhabitatsofseveralplantsandanimals.Pollution isanotheragentthatbringschanges inhabitats.Pollutionharmsthe land,waterorair.Pollution isharmful topeople,animalsandplants. Itdestroysmanyhabitats. Landpollutionaffectstheland,destroyinglife,theenvironmentanditshabitats(Fig.4.10).Airpollutionaffectstheairwebreathein.Factoriesandmotorvehiclesaddairpollutionintheenvironment(Fig.4.11).Airpollutiondamagesourhealthandourenvironment.

Fig. 4.9:Waterpollutiondestroyswaterhabitats.

Fig. 4.10:Litterkillsplantsandcausesanimalstogetsickordie.

Fig. 4.11:Airpollutioncausesacidrainthatcandestroypondorlakehabitats.

Fig. 4.12:Forestscleantheair.Weneedforeststohelpkeeptheairclean.

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Effect of Salts on the Growth of Plants

• 3plasticcups

cupA cupB cupCDay1Day2

Things to think

1. Howdidsaltinthehabitatchangethegrowthofplants?2. WhydidmoreplantsgrowinthecupA?

Number of seeds germinating to plants

Activity 4.2

How to Protect Habitats

Everyonecanhelpprotecthabitatsbysavingtheresources.Reducing,reusing,andrecyclingarethreewaystosaveresourcesandprotectecosystem.• Reducemeanstocutdownontheuseofresources.

• Reusemeansnottothrowawaythingsthatcanbeusedagain.

• Recycle meanstomakenewthingsfromtheusedmaterial.

Procedure1. Makeholesinthebottomofplasticcupswithanail.2. LabelthecupsA,BandC.3. Fillthecupstwo-thirdwithgardensoil.4. Sow8watermelonseedsineachcup.5. AddsomenormalwatertocupA,saltwatertocupBandverysaltywatertocupC.6. Everydayaddsomemorewatertoeachcup.7. Observethecupseverydayfortendaysandcollectthedata.

You will need• gardensoil • 24watermelonseeds

• normalwater • saltywater • verysaltywater

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4.3.2: Adaptations of Organisms to Live in a Habitat

Plantsandanimalsliveindifferenthabitats.Theydevelopspecialfeaturesthathelpthemtoliveintheirhabitats.Thesespecialfeaturesarecalledadaptations.Anadaptationisachangeintheorganism’sbodyorbehaviourthathelps it tosurvive in itshabitat.Organismsthatarenotwelladaptedtotheirhabitatsmaynotsurvive.Aquatic Habitats

Animalsandplantslivinginaquatichabitatshavesuchbodypartsthathelpthemtoliveinwater.1. Streamlinedbodyshapeisanimportantadaptationforanimalstomoveeasilythroughwater.2. Webbedfeetofducks,seagullsandfrogsworklikeoarstohelpmoveinwater(Fig.4.13).3. Floatingplantslikewaterhyacinth,duckweedandwaterlilyhavefloatingleavesandsubmerged

roots.Theirbodiescontainairspaces.Theirleaveshavewaxycoveringtopreventwaterfromcollectingonthem.

Land HabitatsAnimalsandplantslivinginlandhabitatsalsohaveadaptationstoadjustwellintheirsurroundings.1. Thearcticfoxandpolarbearhavethickfurontheirbodies.Thisthickfurkeepsthebodyof

theseanimalswarminfreezingcold.Snowyowlhasathickcoatoffeathers.2. Plantsandanimalsofdesertsareadaptedtoliveinscorchingheat.Somedesertplants

havetough,thicksurfacesandthin,spinyleavestoreducewaterloss.Mostanimals,suchasgecko(lizard)andjackrabbitconservewaterbylivingundergroundduringthedayandcomingoutatnight.Camel’sfeetandlargestomacharetheadaptationstoliveindeserts(Fig.4.14).

3. Birdsong,theroarsoflions,howlingofwolves,etc.aretheadaptationsofbehaviour.Animalssendandreceivemessagesusingsound(Fig.4.14).

4. Plants,too,havemanyadaptationstohelpthemsurvive.Treesinrainforestsgrowverytalltogetthesunlight(Fig.4.14).

Fig:4.13:Webbedfeetofafroghelptomoveinwater.

Extend Your ThinkingAlltheplantsandanimalsofanaquatichabitatwillfinddifficultiesinlivinginotherhabitats.

Why?

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4.4: Biotic Components and Their Relation with Food Chains and Food Webs

Everylivingthingneedsenergy.Energyinanecosystempassesfromoneorganismtoanother.ThebasicsourceofenergyonEarthissunlight.Plantsusesunlightandmakefood.Thus,plantsarethe producers.Animalscannotmaketheirownfood.Theyeatplantsorotheranimalsthateatplants.Thus,animalsaretheconsumers.Aconsumermaybeaprimaryconsumer(herbivore),asecondaryconsumeroratertiaryconsumer.Organismseatorganismsandareinturnbeingeatenbyothers.Thisfeedingrelationshipamongorganismsiscalledafood chain.Mostfoodchainsstartwithproducerslike:

grassgzebraglionleavesgcaterpillargbirdghawkGreenplantsareproducersso,theyarethefirstinmostfoodchains.Animalsthatfeedonplantsare the second in a food chain. Theyare calledprimary consumers.Animals that eatprimaryconsumers are called secondary consumers. Secondary consumersmay be eaten by tertiaryconsumers.

Tidbit

Thechameleoncanchangeitscolourandhasalongsticky-tippedtongue.Theseadaptationshelpittocatchinsects.

Fig. 4.14:Someadaptationsinanimalsandplants

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(b)Writedowntheproducers,primaryconsumers,secondaryconsumersandtertiaryconsumersinfoodchainsconstructedinpart(a).

Aplantorananimalinafoodchainiscalledalink.(a)Constructtwofoodchainswith(i)threelinks (ii)fourlinks

Activity 4.3 Food Chains

Food Web

Anorganismcanbeapartofmanyfoodchains.Severalfoodchainsinanecosystemoverlaptoformanetworkcalledfood web.

Example 1: Aliondoesnotfeedentirelyondeerbutitalsohuntscowsandgoats.Similarlyowlandhawkmayalsotakedifferentorganismsastheirfood.So,mostanimalsfeedononeormorethanonekindofanimals.Thereforemanyfoodchainsformakindofnetworkorafoodweb.Example 2: Asnakedoesnotfeedonfrogalone.Italsoeatsbirds,ratsandevenrabbits.Birdseatgrains.Theyalsoeatinsects,spidersandworms.Ifwearrangefoodchainsinanecosystem,ittakestheformofaweb(Fig.4.15).

Extend Your ThinkingEventhoughsecondaryconsumersdonoteatplants,howareplantsimportanttotheirfood

supply?

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Fig. 4.15: Severalfoodchainsarepresentinafoodweb.

Extend Your ThinkingWhatwillhappentoallanimalsofafoodweb,ifgreenplantsareremoved?

Science, Technologyand Society

Bacteriaandfungiaredecomposers.Theybreakdownthedeadbodiesofplantsandanimals into simplersubstances.Thesesubstancesmixwithsoilandagainareavailabletogreenplantstomaketheirfood.Withoutdecomposersrecyclingofnutrientsisimpossible.Howcanweusedecomposerstoreducetheuseofexpensivechemicalfertilizersinourcountry.

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• Ecosystemisthesystemformedbytheinteractionoflivingorganismsandnon-livingthingsinanenvironment.

• Ahabitatisthenaturalhomeofanorganismwhereitlivesandreproduces.• Grasslandisagrassy,windy,partly-dryarea.Apondhabitatisrichinlife.Desertarethedriest

landareaswithafewnumberofplantsandanimals.Alargenumberofplantsandanimalsisfoundinarainforest.

• Plantsandanimalsadapttoliveinaparticularhabitat.• Lightintensity,temperature,water,droughts,floods,earthquakes,etc.arethefactorsthat

canbringchangesinahabitat.• Peoplecanalsobringchangesinhabitatsbyaddingpollution.• Animalsandplantsadapttotheirenvironmentfortheirsurvival.• Greenplantsmakefood,sotheyareproducers.Animalseatplantssotheyareconsumers.• Afoodchainandafoodwebarefeedingrelationshipsamongorganisms.• Thefeedingrelationshipamongorganismsiscalledafoodchain.• Severalfoodchainsinanecosystemoverlaptoformanetworkcalledfoodweb.

1. Complete each of the following sentences by writing the correct term.i.Thebasicsourceofenergyforeveryecosystem__________ii.Anylivingthingintheenvironment__________iii.Allthepopulationslivinginanareamakea__________iv.Severalfoodchainsoverlapina__________v.Breakdownthebodiesofdeadanimalsandplants__________3. Give short answers.i.Whatkindsoforganismsarethereatthestartofmostfoodchains?ii.Namebioticfactorsofanecosystem.iii.Howareproducers,consumersanddecomposersrelatedtoeachother?iv.Defineanecosystem.v.Whatdoyoumeanbycommunityinanecosystem?vi.Namethewaysbywhichwecansaveournaturalresources.

Questions

Key Points

4. What is a habitat? Describe its few kinds.5. Describe factors that can bring daily and yearly changes in the habitat.6. Describe adaptations of some aquatic animals to live in their habitat.7. Explain a food chain and a food web with examples.

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i.Nametheproducerinthefoodweb.___________________________________________________________________ii.Fromwheredoestheproducergetsenergy?___________________________________________________________________iii.Namethreeconsumersinthefoodweb.___________________________________________________________________iv.Writedowntwofoodchainsinthisfoodweb.___________________________________________________________________

Q8. Look at the following food web and answer the questions given below.

CHAPTER

5 Water

Animation 5.1 :Water MoleculeSource and credit: eLearn.punjab

http://elearn.punjab.gov.pk/

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5. Water eLearn.Punjab

Students’ Learning Outcomes After completing this chapter, the students will be able to:• Describe the ways in which clean water is vital for meeting the needs of humans and other

living things.• Identify the sources of water.• Recognize the substances present in water that make the water impure.• Suggestdifferentwaystocleantheimpurewater.• Describe various uses of water in our country.• Investigate the consumption of water in our daily life and suggest ways to reduce wastage of

water.

All is born of water. (Al-Quran)

Living things are all around us. They are in air, on land and in ...

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