1.ecosystems (1)

copyright 2005-2006 keep it simple sciencePreliminary Biology Topic 1

Liverpool Boys High School SL#702296

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Preliminary Biology Topic 1

A LOCAL ECOSYSTEMWhat is this topic about?To keep it as simple as possible, (K.I.S.S.) this topic involves the study of:1. DISTRIBUTION & ABUNDANCE OF ORGANISMS

2. BIOTIC & ABIOTIC FACTORS 3. ROLES & RELATIONSHIPS

4. THE FLOW OF ENERGY & MATTER5. ADAPTATIONS TO ENVIRONMENT

6. HUMAN IMPACTS

but first, some definitions...Ecologyis the study of living things and their environment, and allthe inter-relationships between the life-forms and thefactors of the environment itself.

EcosystemAn ecosystem comprises all the living things and the non-living environment of a particular, defined area. The size ofan ecosystem can vary enormously... you might study theecology under one rock, or in a lake. You might consideran entire mountain range as one ecosystem, or an entireocean. Ultimately, the entire Earth can be considered as asingle ecosystem.

Photo by Diana

Communityrefers to all the living things within an ecosystem... all thedifferent types and individual organisms.

Populationrefers to all the individuals of a particular species livingwithin the ecosystem. The community within a complexecosystem such as a coral reef, or a tropical rainforest,contains thousands of populations of different species.

AN AUSTRALIAN ECOSYSTEMsun

THE SUN PROVIDESALL THE ENERGY FOR

THE ECOSYSTEM

The temperature, amount of light, theair, water and the soil are vital non-

living factors of every ecosystem

The plants and animals interactwith each other, and with the

non-lliving environment



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Quadrats&

Capture-Recapture

TransectStudies

AbioticFactors

BioticFactors

Parasite&

HostPredator

&Prey

Commensalism

Competition

Mutualism

Allelopathy

Cycling of matter.

Flow of Energy

FoodChains

FoodWebs

BiomassPyramids

StructuralPhysiologicalBehavioural

Loss of HabitatPollutionEutrophicationAlien Species

AA LLOOCCAALLEECCOOSSYYSSTTEEMM

Distribution&

Abundance

Factors ofan Ecosystem

Roles&

Relationships

Flow ofEnergy & MatterAdaptations

toEnvironment

HumanImpacts

CONCEPT DIAGRAM (Mind Map) OF TOPICSome students find that memorizing the OUTLINE of a topic helps them learn and remember the concepts andimportant facts. As you proceed through the topic, come back to this page regularly to see how each bit fits thewhole. At the end of the notes you will find a blank version of this Mind Map to practise on.

The first questions you might ask when beginning to studyany ecosystem are:

which organisms live here? where do they live, exactly? how many of them are there?

DISTRIBUTION in ecology refers to wherewithin an ecosysytem the individuals of a species arelocated.

Some species might be more or less evenly distributedthroughout the area being studied, but often the populationof a species is clumped together, or found only in certainparts of the environment.

How a species is distributed gives clues about how it isinteracting with the environment. For example:

So, one of the first things to do when studying anecosystem is to study the distribution of the organismspresent. One good way to do this is by carrying out a...

Transect StudyA Transect is like a cross-section through a study area.

The idea is to define a line which cuts right across the areabeing studied. This could be a string line or a series ofmarker sticks hammered into the soil.

The study is done by moving along the line and noting andrecording which species are located at each point.

Often plants are the main subjects of a Transect Study,because many animals move around so far and so quicklythat they cant be studied this way.

An animal that isusually found in treetops may be there tofind its food, or may

be escaping itsenemies.



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1. DISTRIBUTION & ABUNDANCE OF ORGANISMS

A plant found mainlyalong the banks ofcreeks or rivers mayhave a greater need forwater to grow, or mightonly be able toreproduce by spreadingits seeds in water.

A Study of Distribution at a Rocky SeashoreIn sea-shore studies it is quickly discovered that thedifferent organisms tend to be found in quite distinctzones which are related to the vertical heights above andbelow the tide levels.

Exactly where each species is found is an indication of theinteractions in the ecosystem between each species andfactors such as:

FOOD SUPPLIES they need to be near. PREDATORS they need to avoid. WAVE ACTION.

Most of the organisms along the sea-shore are welladapted to withstand the pounding of waves.

EXPOSURE TO AIR.Sea-shore animals are all sea creatures which can with-stand being exposed for a while at low tide. How well theycope with this often determines their exact distribution.

You may have done a Transect Study as part ofyour practical work, or on a field trip excursion.

For schools near the coast, a common field tripis to study the rocky seashore environment.

TTRRAANNSSEECCTT DDIIAAGGRRAAMM OOFF AA RROOCCKKYY SSEEAASSHHOORREE

High Tide level

Blue periwinkles

Neptunes necklace seaweed

Low Tide level

30 metres

3 m

etre

s

Note: Vertical scale exaggerated

CrabsBlack & striped periwinklescommon here

Brown bubble weed

Sea Urchins & Starfishcommon here

Kelp seaweed only foundat lower levels

SeaUrchin

Barnacles



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ABUNDANCE refers to how many individuals arein the population of a species in the ecosystem.

In some cases, especially large organisms in relatively smallareas of study, it can be easy enough to count thepopulation directly. For example, to find the abundance offig trees in a small forest, simply walk back-and-forth in agrid pattern and count as you go.

Hovever, small organisms, large areas and animals that hideor move around a lot make direct counting impossible. Inmany cases, abundance of a species must be done bysampling... studying small samples of the environment,then scaling the data up to the whole area.

Two commonly used sampling techniques are:

Quadrat SamplingA quadrat is a simple wire/wooden/plastic frame whichis dropped onto the ground at random throughout thestudy area.

At each quadrat drop the number of the species ofinterest is counted. After a number of drops (the more,the better) the average number of organisms per quadrat iscalculated. Finally, the estimated population is found byscaling-up from the area of the quadrat to the total areabeing studied.

The quadrat has been dropped 8 times. The numbers oftarget plants in each quadrat drop were 2,1,0,3,1,1,1,1.This gives an average of (10/8) = 1.25 plants per drop.

Estimated = Average count x Study area Population per quadrat Quadrat area

For this example: Estimated = 1.25 x 64 Population 1

= 80 plants in this area.

Remember this is an estimate only, and can be improved byincreasing the number of quadrat drops.

EEXXAAMMPPLLEE OOFF QQUUAADDRRAATT SSTTUUDDYY

KEY:

Plant studied

Quadratdrops

8 metres

8 m

etre

s

StudyArea= 8x8= 64 m2

Capture-Recapture Sampling.The obvious problem with the Quadrat method is that itdoes not work with animals that will run/fly/swim awayfrom you.

For mobile animals, or secretive, hard-to-find types, thecapture-recapture technique can be useful.

For the example shown, 10% of the 2nd capture aremarked. So statistically, the 1st capture sample of 100 mustrepresent 10% of the total population of the study area.Therefore population estimate = 1,000 individuals.

Mathematically,Estimated = 1st capture x 2nd capture

Population no.marked in 2nd capture(no. re-captured)

= 100 x 200 20

= 1,000 individuals

LimitationsThis technique relies on the marked/tagged individualsmixing randomly back into the population and being re-caught again at random. Sometimes this doesnt happen.

For example, intelligent mammals learn to avoid the trapsor nets, or may even enjoy being caught (for the food in atrap) and learn to seek out the traps. Either way, this canmake the population estimate inaccurate.

1. Capture a numberof the species beingstudied.

Example: 1st Capture = 100individuals

2. Mark or tagthe animals

3. Release animals backwhere they werecaptured.

4. Carry out a secondcapture program.

Example: 2nd Capture = 200individuals

5. Count how many of the2nd capture are markedfrom the 1st capture.

Example: Out of 200 in the 2nd capture,20 are marked = 10% marked.

1 m2

wait...



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Worksheet 1Fill in the blank spaces.Check your answers in the Answer Section.

Distribution in ecology refers to a)..................a species is located in an area. This gives cluesto how a species is b)............................................with the environment. For example, an animalfound predominantly in treetops might bethere to find c)........................, or it may bed)....................................... from its enemies. Agood technique for studying distribution iscarry out a f)..........................................study.This is where you work along ag)..................................... across the study area,noting h).............................................................at each point.

i)...................................... refers to how manyindividuals of a species are in an environment.One way to estimate this is by droppingj).................................... at random throughoutthe area. At each drop you count how manyorganisms are in the quadrat. At the end youcalculate the k)............................... per quadrat.Knowing the area of each quadrat, and thearea of l)................................................., the totalpopulation can be estimated. The accuracy willbe improved by m).......................................................................................

For animals that move around a lot, theabundance is best estimated by then)........................................................ method.This involves capturing a sample of thepopulation, then o).......................................them in some way, and thenp)..................................... them again. Later, youcarry out a second q)..............................., andcount how many of the sample arer)................................... This allows calculationof an estimate of the s).....................................One limitation of this technique is that it relieson the captured specimenst)...............................................................................,but this doesnt always happen.

WHEN COMPLETED, WORKSHEETS BECOME SECTION SUMMARIES

Quadrat Study Problems1.Abundance of starfish on a rock platform wasstudied by the quadrat method. The quadrat wasa plastic frame with an area of 0.25 m2.The rock platform was a rectangle approximately20m x 30m.

The numbers of starfish in 10 quadrat dropswere: 8, 0, 14, 11, 3, 1, 0, 0, 7, 2.

Estimate the starfish population on the rockplatform.

2.A farmer wished to estimate the populationabundance of a noxious weed species in apaddock measuring 300 x 400 metres. He used arectangular wire quadrat frame 1.0 x 0.5 metre.The number of target weeds in 20 quadratdrops were: 2, 8, 0, 15, 11, 0, 2, 1, 0, 9, 16, 3, 7,13, 0, 1, 7, 0, 8, 2.

What is the approximate population of weeds inthe paddock?

Capture-Recapture Problems1.A capture-recapture study was carried out on thelizard population on an island. In the first captureexercise, 230 lizards were captured, tagged andreleased.

A week later, 156 lizards were captured. Of these,18 had tags from the 1st capture.

Calculate an estimate of the lizard population onthe island, to the nearest thousand.

2.To estimate the possum population in area, 65possums were captured unharmed, tagged andreleased. A week later 48 possums were captured.Of these, 12 had tags.

Estimate the possum population.

It was later found that the possums ratherenjoyed being trapped because of the tasty foodused as bait. Does this mean your populationestimate may be too high or too low? Explain your answer.



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2. BIOTIC & ABIOTIC FACTORS OF AN ECOSYSTEM

The distribution and abundance of any species within anecosystem depends on a whole host of factors...

examples...Food organisms Availability of waterPredators Availability of oxygenDiseases Light intensityCompetitors Temperature range

Soil characteristicsSalinityAcidity (pH)Exposure to wind

Comparison of Abiotic Characteristics:Terrestrial Environment / Aquatic Environment

(on land) (in water)

Viscosity is a measure of the stickiness of a substance,and how easy or difficult it is to move through it. On land,plants and animals are surrounded by air, which has verylow viscosity and is easy to move through.

Water has a much higher viscosity and is more difficult tomove through. As a result, many aquatic animals arestreamlined, and equipped with powerful tails for propulsion.

Buoyancy is a measure of flotation ability. Water is verybuoyant and supports plant and animal bodies against thepull of gravity. Aquatic organisms do not need strongstems or legs to hold themselves up.

Terrestrial plants need strong stems or trunks of wood togrow upwards against gravity. Animals need strongskeletons.

Temperature VariationOn land the temperature can easily vary 20oC from day tonight, and even more from summer to winter. Living thingsmust be able to cope with that while maintaining relativelystable internal body temperatures. Terrestrial animals needfur or feathers for insulation, or have physiologicalresponses such as sweating or shivering, or alter theirbehaviour (sunbaking or seeking shade) in response to heator cold.

Water-living organisms generally do not need such specialadaptations. Aquatic environments have very stabletemperatures and change very little, even between summerand winter.

Availability of Gases (oxygen & carbon dioxide)Since the air is about 20% oxygen, it is readily available interrestrial environments. Carbon dioxide (needed by plantsfor photosynthesis) is only 0.035% of air, so land plants areoften limited by this.

These gases do NOT dissolve well in water, so theconcentration of gases in aquatic environments is very low,and gets lower as the water gets warmer. For this reason,fishs gills have to be highly efficient to extract the necessaryoxygen, and are far better than our lungs for gas exchange.

Availability of WaterTerrestrial environments are subject to evaporation, andplants and animals must have ways to conserve water, byhaving water-proof skin, or avoiding losses duringexcretion. This problem becomes extreme in someenvironments such as deserts.

In aquatic habitats the organisms are surrounded by water,but there can still be problems due to osmosis. This will bestudied in the next topic, but in summary:

In salt-water environments animals can lose water byosmosis and must constantly replace it.In fresh water, osmosis causes water to flow into theorganisms body and must constantly be pumped outagain.

Biotic Factors(biotic = living)

Abiotic Factors(non-living)

SSTTRREEAAMMLLIINNIINNGG

Most of body is muscleto power the tail

Strongtrunk tohold leavesup to catchlight

Bony skeletonsupports bodyagainst gravity

SSAALLTTWWAATTEERR FFRREESSHH WWAATTEERRFFIISSHH FFIISSHH

Mustdrinkconstantlyto replacewater loss

Osmosis suckswater from body.

Mustexcretewaterconstantly

Absorbs water



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Availability of LightLight is essential for plants to carry out photosynthesis.This process makes all the food, so the availability of lightis a critical factor in any ecosystem.

Light penetrates through air very easily, so most terrestrialenvironments get plenty of light for the plants. The floorof a rainforest is an exception... here the dense canopy oftrees means very little light penetrates to reach the smallerspecies or seedlings.

Rainforest plants have adapted to this in many ways:

Epiphytes (e.g. staghorn ferns) germinate and grow highup in other plants and so avoid the darkness below.

Plants living on the floor have large, broad leaves, packedwith extra chorophyll, to absorb what little light is available.

In contrast to air, water does NOT allow light through soeasily. Light can penetrate the surface layers easily enough,but even just 10 metres deep, much of the light has beenabsorbed, and by 100 m down it is totally dark.

Also, water does not absorb all the different colours(wavelengths) equally. Red and orange are absorbed rapidly,while green and blue penetrate deeper into the water.

Most seaweeds are not the familiar green of land plants.Many are brown or red because they contain specialpigments to absorb the dominant blue wavelength of lightthey receive.

In deep ocean waters there is no light and consequently noplants. Deep ecosystems rely on dead organic remainsdrifting down from above for their food supply. On thedeep ocean floor, some ecosystems are based on foodmade by chemosynthesis around volcanic vents. This willbe explained in a later topic.

Blue light penetrates to greater depth

Red light isabsorbed near

the surface

Many seaweedshave specialpigments to

efficiently absorbthe available

light.

Different colours(wavelengths)

of light penetrate water todifferent depths.

Birdnest fern epiphytein a rainforest tree

Brown Kelp Seaweed

Photo courtesy ofKatia Grimmer-Laversanne

Photo by Diana



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Worksheet 2

Divide these ecosystem factors into 2 lists... theBiotic and Abiotic factors.

Light, prey, diseases, oxygen, water, predators,soil, temperature, food plants, exposure,competitors, acidity.

Fill in the blanks.Check your answers in the Answer Section

In comparing the a)...............................................(on land) environment with theb)...................................... (in water) environment,a number of Abiotic factors are very important;

c).................................. refers to how easy/difficultit is to move through the medium. Air has a veryd).............. ........................... while water is muche).......................................... Because of this,aquatic animals often have a f)..............................shape.

Buoyancy is a measure ofg).................................. ability. Water is muchh)....................... (more/less) buoyant than air.Terrestrial animals and plants need strongi)............................... structures to withstandgravity, while aquatic organisms are supported bythe water.

Comparing temperature variations, the terrestrialenvironment shows j).....................................variation than water. Thats why many landanimals have special features such ask)................................ for insulation, or the abilityto l)................................... when too hot.

Important gases like m).......................... areabundant in the air Gases do notn).............................. very well in water, so aquaticanimals need very efficient o).................................or other breathing organs.

On land, plants and animals must have ways top)............................................... water and avoiddehydration. This could involve havingq)....................................... skin, or avoidingexcessive water loss during r)....................................In aquatic environments there can be waterproblems too, due to the process ofs)......................................................For example, salt-water fish constantlyt)....................................... water, while fresh-waterfish need to constantly u).............................. water.

On land, availability of light is generally not aproblem, except in environments suchv).......................................... To cope with this,epiphyte plants such as w)................................,grow up in the tops of trees. Plants on the floormay have leaves which arex)..................................................................................to absorb any light available.

In water, light penetration is poor, and thedifferent y)............................................... of lightpenetrate differently. z)........................ wavelengthsare absorbed rapidly, while aa)..................................penetrates further. Seaweed plants often havespecial ab)................................ (often red/brown incolour) to better absorb the available light. In thevery deep ocean there is no light, and noac)...................................... can survive there.Ecosystems must rely on ad).................................drifting down from above, for food, or onae).......................................... around volcanicvents.




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3. ROLES & RELATIONSHIPS BETWEEN ORGANISMS

Ecology is very much about relationships. This sectionlooks at some of the ways that different species within anecosystem relate to each other.

Predator - PreyAlthough animals eat living plants, this is not predation...the term is reserved for situations where one animal eatsanother.

examples... Predator PreyDingo eats WallabyLion eats ZebraSpider eats InsectDolphin eats Fish

Both predator and prey have major impacts on each othersdistribution and abundance, and each can cause the otherspopulation to rise and fall in a fairly regular pattern.

Notice that Predator abundance is always lower than prey.

(Reasons for this are explained in the next section) The peaks and troughs of the predators population

always occur after those of the prey species.

What happens:1. The numbers of the prey species increase because of its

breeding cycle, or seasonal increase in available food.2. This provides more food for predators, who survive in

greater numbers and reproduce more sucessfully.3. As predator numbers increase, more prey get eaten and

so the prey population decreases.4. As prey numbers decline, less predators can survive, and

breeding is less sucessful... predator numbers decline.

EACH ORGANISMS ABUNDANCE AFFECTS THEOTHERS ABUNDANCE.

CommensalismCommensalism is a relationship in which one organismbenefits while the other is neither harmed nor helped.

A good example is the remora, or sucker fish whichattaches itself to a shark with a suction cup structure andhitches a ride. It does the shark no harm at all. When theshark feeds, the remora feeds on the debris and scrapsfrom the sharks meal.

A simple example of commensalism is a bird nesting in atree. The bird family gain the important benefit of arelatively safe and secure nest site, while the tree neithergains nor loses.

Another example, seen commonly in rural areas is thecattle egret (bird) which follows the cattle through thepastures, feeding on the insects which are disturbed by thecows. The cow neither gains nor loses from therelationship.

TIME (years)

Popu

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PREY SPECIES

PREDATOR SPECIES

Populationpeaks

Shark with remora hitching a ride.

Photo by Pam RothCreatingOnline.com



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MutualismIn a mutualistic relationship, both species benefit.Mutualism is much more widespread in nature than isgenerally realized.

The classic example is the honey bee and many floweringplants. The bees total food supply is nectar and pollen fromthe flowers. As the bee gathers its food the plants gain theessential service of pollination of their flowers. Both benefitso profoundly that neither can survive without the other.

Many grazing animals (e.g. kangaroos) eat a diet rich inplant cellulose which is nutritious but difficult to digest.These animals have a population of mutualistic microbesliving in their gut. The microbes are able to break thecellulose down and make its nutrition available to theanimal, while the microbes gain a secure, stable place to liveand a permanent food supply... both benefit.

A mother koala will regurgitate pap from her gut to feedher baby. The pap contains the mutualistic bacteria that thebaby must have to digest the tough gum leaves.

Another example is coral. The coral animal is a polyp... asoft, hollow animal related to jellyfish. Inside the polypsflesh lives another organism, an alga (microscopic plant).

The polyp provides a secure home for the alga, which pays itsway by sharing the food it makes by photosynthesis. Bothorganisms gain tremendous benefits from the relationship.

Parasite - HostParasitism is a relationship in which one organism feeds on another withoutkilling it, or even necessarily harming it significantly.

Some parasites, such as tapeworms, live inside their host andabsorb digested food without doing much harm. This way the

host stays healthy and the parasite has a secure home andguaranteed food supply.

Other parasites, such as leeches and ticks, are casual parasiteswho attach to a host, take a feed of blood, and then drop off and

live independently until it is time to feed again.

More serious are the many micro-organisms which can causeinfectious diseases. These parasites include bacteria, viruses and a

few protozoans and fungi. They invade the hosts body, feedingand reproducing so that the host becomes sick and may even die.

Allelopathyis a relationship found particularly among plants and

fungi, in which one organism directly inhibits thegrowth and development of others by releasingtoxins. The famous antibiotic penicillin was

discovered in the fungus Penicillium because of itsinhibiting effect on the growth of bacteria.

Some trees and shrubs (including the pest weedlantana) release inhibiting chemicals from theirroots. These inhibitors slow down or preventthe germination and growth of the seeds and

seedlings of other plants.

Photo by Norbert Machmek

Photo by Diana



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Competitionoccurs whenever two different species need to use exactlythe same resource, in the same way. The resource inquestion may be a food source, or nesting sites or simplyliving space, such as when plants like lantana or bitou bushcover areas at the expense of other plants.

Competition usually results in a winner and a loser. Onespecies will be slightly more successful than the other, andits population will grow, while the less sucessful competitorwill decline in numbers and may eventually become extinctin the ecosystem.

Sometimes what seems like competition turns out not to be.For example, the lion and the leopard are both large Africanpredators, often living in the same areas and both feedingon the herds of grazing animals.

However, careful study reveals that their hunting techniquesare so different that they tend to prey on different speciesand different categories (e.g. young rather than adults) sothey are in fact NOT competing and can both survive in thesame habitat.

It is known from fossils that the Thylacine (Tasmaniantiger) was once widespread as one of the main predatorson mainland Australia. However, its numbers rapidlydeclined after the introduction of the dingo from Asiaabout 10,000 years ago.

It seems the dingo was a more sucessful predator and out-competed the Thylacine on the mainland. The dingo wasnever introduced to Tasmania, so there the tigers surviveduntil driven into total extinction by the impacts ofEuropean settlement.

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Worksheet 3Fill in the blanks. Check your answers in the Answer Section

An animal which kills and eats another animal is called aa)......................................... The animal it eats is itsb)............................ Each ones population abundance affectsthe other. For example, if the predator populationincreases, the prey population will c)......................................because d)........................................................................ On agraph, the peaks & troughs will match each other, but thepredators graph will always be e).........................................and f)................................................. than the preys graph.

A parasite is an organism which g).......................................on its host without h).................................... A good exampleis the i)............................................. which lives in the gut ofits host, eating the digested food. Other parasites such asj)...................................... and ................................................feed on the hosts blood.

A relationship in which one organism gains an advantage,while the other neither gains nor loses, is calledk).............................................................An example is theshark and the l)..........................................................

Mutualism is when 2 organismsm)..................................................................................................A good example is the n)..................................... and................................................... Many grazing animals gethelp to digest the tough fibres of plant food frommutualistic relationship with o)....................................... livingin their gut.

Some plants and fungi produce chemical toxins whichp)............................................ the growth of other organisms.This relationship is called q)......................................................

Competition is when 2 organisms both need to user)................................................................... in an environment.Usually, the result of competition iss).....................................................................................................


Dingo

Photo by Pau Talan

Photo by Alex Maher

Photo by Mark Karstad



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4. THE FLOW OF ENERGY & MATTER IN AN ECOSYSTEM

Cycling of MatterWithin any ecosystem the important chemicals of life tendto be re-cycled.

The water cycle of nature is well known, and you shouldbe familiar with the Oxygen-Carbon cycle.

Other chemicals that are recycled within ecosystemsinclude Nitrogen, Calcium and Phosphorus... in fact ALLthe chemicals get used over and over again.

Energy Inputs & OutputsUnlike the chemicals, energy cannot be recycled. As it isused it must be replaced from outside the ecosystem.

The ultimate source of ALL the energy in an ecosystem isthe SUN. The Sun provides the heat to keep eachecosystem at a livable temperature, but more importantly itis the LIGHT of the Sun which powers all life.

How Organisms Use EnergyEverything that an organism does requires energy.

Organisms:-MoveGrow and Repair body tissueReproduceSeek, Eat and Assimilate their foodRespond to things happening around themKeep their bodies warm

Cellular Respirationis the process which releases the energy stored in food. Ittakes place in every living cell on the planet and afterphotosynthesis (next topic) has got to be the next mostimportant biological process on Earth.

Although the process can be witten as a simple chemicalreaction, this is very deceptive. Cellular respiration actuallytakes place as a sequence of about 50 chemical steps... theequation above is merely a summary of the overall process.

Dont forget that the essential product of respiration is theenergy-carrier ATP. The CO2 and H2O are merely wasteproducts to be recycled in the ecosystem like all chemicals.

A common misconception is that plants doPHOTOSYNTHESIS and make food, while animalsdo RESPIRATION to use the food.

Its true that plants do photosynthesis and make all thefood on Earth, but respiration is carried out by all livingthings... animals AND plants.

Luckily for us animals, the plants carry out enoughphotosynthesis to feed themselves, AND produce a surplusto feed us as well.

SSUUNN

Light PLANTScapture light energy

duringPhotosynthesis

Energy is stored in the FOODproduced by plants

All organisms use the energyin food to power their life

functions.The process of Respirationreleases the energy in food.

INPUT

OUTPUT

wasteheatenergy

Glucose + Oxygen Carbon + Water (sugar) Dioxide

Waste products

Major energycompound infoods

in air

ATP

Energy-carryingchemical used inall cells to powerlife processes.

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C6H12O6 + 6O2 6CO2 + 6H2O

energy transfer ATP

Respiration

ANIMALSPLANTS

CO22

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Photosynthesis



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Food ChainsPlants are food PRODUCERS.

They capture light energy by the process of photosynthesis, and store it as the chemical energy in food.

All other organisms are CONSUMERS of food. They rely on eating the plants or other animals.

So, in any ecosystem there is a chain of feeding, based on the plants... a food chain.

GRASS KANGAROO DINGO

Plant Herbivore Carnivore

Producer 1st order 2nd orderConsumer Consumer

1st Trophic 2nd Trophic 3rd Trophiclevel level level

(trophic refers to feeding)

NOTES:1. The arrows in a food chain show the direction that the energy flows. The arrows must never be reversed.

2. Note the different ways to describe each organisms role in the chain. Be careful not to confuse the different methods...e.g. a 1st Order Consumer is at the 2nd Trophic Level... etc.

The Role of the DecomposersAll along the food chain organic wastes are produced. Deadleaves from plants, body wastes and shed skin and fur from theanimals are just a few examples.

This left-over waste material is food for a very important groupof organisms... the decomposers. The main decomposerorganisms are the microscopic bacteria and the soil fungi. Theseorganisms feed on the scraps and wastes and in doing so, causewastes to decay and be broken down into very simple chemicalssuch as CO2 and nitrate and phosphate ions.

THIS IS ESSENTIAL TO THE RECYCLING OF THECHEMICALS IN AN ECOSYSTEM.

Not only do the decomposers get rid of all the yucky stuff and clean up the environment, but they ensure that the vitalchemicals are recycled into the air or soil for re-use by theplants... ...and so the food chains continue....

Mushrooms and toadstools are thereproductive structures of soil-lliving fungi

PPhhoottoo bbyy DDiiaannaa

Photo by Alex MaherPhoto by Diana



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Food WebsAlthough we can best understand the flow of energy by a food chain,

in fact simple food chains never exist by themselves in nature.

Kangaroos dont just eat grass, and dingoes dont just eat wallabies.

The real feeding relationships in an ecosystem can only be described by a food web...many inter-connected food chains.

A food web diagram allows us to analyse the flow of energy(stored in food) through the ecosystem and to make certainpredictions...

Example Questions and Answers:Question:Which organism is at the highest Trophic Level above?Answer:The large fish, which is at the 5th trophic level.

large fish(5th)

octopus (4th)

mussels (3rd)

zooplankton (2nd)

phytoplankton (1st Trophic Level)

Question:List all organisms which are 1st order consumers.Answer:Limpets, periwinkles, chitons, mussels & zooplankton.

Example: FOOD WEB IN A ROCK POOL large fish

starfish octopus small fish

mussels

limpets periwinkles chitons zooplankton(microscopic animals)

green algae phytoplankton(microscopic plants)

Hints on Constructing a Food WebTo keep it simple and read-able (K.I.S.S.) when constructing a food web:

always start with the producers (plants) at the bottom and work upwards

try to keep the members of the same trophic level in-line in the diagram.(not always possible, because some organisms may be feeding at more than one trophic level...look at the mussels in the diagram above.)

Question:What might be the effect on the mussel population if therewas a large increase in the octopus population?Answer:If there were more octopus they will eat moremussels, so the mussel population would decrease.

Question:If a disease wiped out all the mussels in a particular area,what effect might this have on the chiton population?Answer:(Chitons are not directly connected to mussels, so youmight think thered be no effect, but there might be...)If there are no mussels to eat, the octopus might eatmore chitons. Therefore the chiton population coulddecrease.ORWithout mussels to eat, the octopus might eat morestarfish. This could mean less chitons being eaten bystarfish so the chiton population could increase.

THIS DEMONSTARTES THE DIFFICULTY OF MAKINGPREDICTIONS ABOUT NATURAL FOOD WEBS... CONSEQUENCES

OF CHANGES CAN BE QUITE UNPREDICTABLE!



15

You are what you eat goes the old saying, and it is literallytrue that every molecule of your body is built from thechemicals that you have eaten as food over your lifetime.Your body weight is your Biomass... the mass (weight) ofliving flesh in you.

An average person eats at least 250 kg of food per year anddrinks at least 500 litres of liquids. So why arent we all asbig as an elephant? Simply because we all produce roughlythe same mass of wastes and excrete them so that ourbiomass stays more or less the same. (Unless still growing,of course).

In ecology, we deal with the total biomass of an entirepopulation, or of the whole community. For example, ifthere are 200 starfish living in a particular rockpool, andeach has a mass (on average) of 50 grams, then the biomassof starfish in the rockpool is 200 x 50 = 10,000 g = 10 kg.

It is always found that the biomass of plants is more thanthe biomass of herbivores, which is more than the biomassof carnivores, and so on. Why?

Everything you do requires energy, which you get fromcellular respiration...

C6H12O6 + 6O2 6CO2 + 6H2O + ATP

...and as you breathe out you excrete the waste CO2 (plussome water vapour) and so lose a little of the mass of thefood you previously ate.

...and as you use the energy of the ATP molecules, theenergy is converted to low-grade heat and dissipates intoyour surroundings. This energy is lost, and cannot be re-used by living things.

In any ecosystem it turns out that about 90% of thefood/energy taken in at any trophic level, is lost as wastesand low-grade heat. (Thank goodness for theDecomposers to get rid of all that waste!)

This means that in a food chain, only about 10% of thebiomass and energy at any trophic level is available to beeaten by the next trophic level organisms. The result is aBIOMASS PYRAMID.

Biomass

2ndTrophicLevel

3rdTrophicLevel

4thTrophicLevel

1stTrophicLevel

PYRAMID OF BIOMASS &

ENERGY

So, for the food chain

GRASS KANGAROO DINGO

if there was (say) 100,000 kg of grass in an ecosystem,then this could not support more than about 10,000 kg ofkangaroos, and only about 1,000kg of dingo biomass.

The approximate population numbers would be:5 million grass plants feeding about 400 kangaroos,feeding just 50 dingoes... a pyramid of numbers too.

This is why very few food chains in nature have more than 5 or 6 trophic levels... the available food & energy becomes too little

Pyra

mid

shap

e

Biomass of Producers(Plants)

10%available

Biomassof

Herbivores

10%

10%

90% of Biomassand Energy lost





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Adaptations are special characteristics that help anorganism survive in its environment.

For example, the black bear of North America has a thickcoat of fur. This is a structural adaptation to itsenvironment. The fur helps insulate the body to keep itwarm in the cold climate in which this species lives.

Other structural adaptations that have already beenmentioned in previous sections include:

streamlining of many aquatic animals to deal with the high viscosity of water

large, broad, chlorophyll-packed leaves of plants living onthe rainforest floor, to cope with the low light levels

the bony skeleton of most terrestrial animals needed tosupport the animal against gravity.

Another category of adaptation is physiologicaladaptation. (Physiological refers to the way the bodyworks or functions) Previously mentioned examplesinclude:

animals shivering when cold, and sweating when too hot

freshwater fish excreting water constantly to removeexcess water from their bodies. This is controlled by thefunctioning of their kidneys.

One of the classic physiological adaptations is the kidneyfunction of many desert animals. In an environment wherewater is scarce, these animals conserve body water byproducing only small amounts of very concentrated urine.

In some cases, such as desert mice, their kidneys are soefficient at retaining water that they do not need to drink,but can survive on the metabolic water produced bycellular respiration.

A third category is behavioural adaptation, which iswhere an animals instinctive behaviour helps it survive andthrive in its environment

Dangers of Inferring AdaptationsYou need to be careful when examining any organism forits adaptations because it may require careful study to besure of the real reason for some characteristics.

For example, it is possible that the adaptation you observecould be inherited from ancestors who lived in a differentenvironment, and it is not a help to survival in the currenthabitat.

Also, its not always easy to decide what survival advantagea particular characteristic may give.

For example:is the magpies colour scheme an adaptation which helps itsurvive because it gives:

camouflage?or temperature control?or sexual attraction for mating?or identification, to keep a group together?

ONLY CAREFUL STUDY WILL REVEAL THE TRUTH.

5. ADAPTATIONS OF ORGANISMS TO THEIR ENVIRONMENT

Example: most reptiles....

sunbake whentoo cool

seek shelterwhen too hot

Photo by Diana



17

Worksheet 4Fill in the blanks. Check answers at the back.

In any ecosystem, the chemical resources tendto be a)..............................................., but theenergy is used up and must be constantlyb)............................................. The source of allthe energy is the c).......................... The energyis captured by the d)......................................inthe process of e)...................................................This converts light energy into the energystored in the f)............................................molecules.

Organisms need energy for all the lifeprocesses such as moving around,g).............................................................. and.................................................................................The energy of food is released by the processof h)............................. ......................................This requires the gas i)..................................The products are the chemical wastesj)...........................................................and................................................. and the energychemical known as k)......................................

Energy is passed from one organism toanother as food, and the flow of energythrough an ecosystem is a l)........................................................... In any food chain, the plantsare the m)................................, and animals aren)...........................................................

The Decomposers are vital to get rid ofwastes and dead scraps and too)....................................... vital chemicals. Singlefood chains rarely exist in nature. Instead, anumber of food chains whichp).................................... with each other, form aq)..................................... ...............................

The total body weight of all the individuals ofa species in an ecosystem is known as ther)................................ There is always about 10times more r)............................... of plants thanof s).............................................. because about90% is always lost as wastes. Because thebiomass decreases rapidly up through anyfood chain it is referred to a biomasst)................................

Worksheet 5

Special characteristics which help an organismsurvive in its environment are calleda).........................................................................Some of these are structural: they involvespecial structures, such as the fur of a bearwhich b)..................................................................in a cold climate. Another example is howmany aquatic animals arec)...................................... to allow them to movemore easily through water, which has a highd)................................................................

The second category of adaptations are thosethat are e).............................................., or relatedto the functioning of the body. For example, ananimal might f).................................... when toohot, or g)................................................ if toocold. Many desert animals have highly efficientkidneys so they produce h).............................amounts of highly i).......................................urine, in order to j)...........................................water.

The third category of adaptations isk).................................................. For example,reptiles cannot regulate their body temperaturephysiologically, so they use behaviours instead.They will l)......................................................when too cool, and seek m)...................................when too hot.




18

Human culture is the learned behaviours we haveaccumulated over the millenia since our ancestors inventedtools, controlled fire and began to rise above nature. Ourculture includes language, art, music, customs andTECHNOLOGY.

It is our over-population, and our complex, industrialtechnology that impacts on natural ecosytems...

Loss of HabitatVery simply, humans clear forests, fill wetlands and divertstreams to make room for our towns and cities and for ouragriculture. For example, only about 3% of Australianrainforests remain, from those present 200 hundred years ago.

Clearing of natural environments is disaster for manyspecies. They are specially adapted to their habitat andcannot survive elsewhere.

PollutionMany human activities produce chemicals which can harmthe environment if released.

Acid rain results from gases such as sulfur dioxide (SO2)released from burning of fossil fuels, especially coal. Thegas dissolves in rainwater forming an acid solution that canseriously affect forests, lakes and wetlands by killing someorganisms so that food chains are disrupted.

Pesticides and industrial poisons, even in very smallamounts can build up in living communities by biologicalmagnification...

example: the level of toxic chemical in a shrimp might bequite low, but a fish which eats many shrimp in a year endsup with a concentration of toxins 100 times higher... and soon up through the food chain.

Scientists are currently alarmed by a world-wide decline inpopulations of amphibians (frogs & toads). It is suspectedthat various human-made chemicals are disrupting thereproduction and development of 100s of species whichare vital links in the food webs in many ecosystems.

Eutrophicationoccurs when rivers and streams are over-fertilized byhuman sewerage and agricultural run-off.

Although our sewerage may be thoroughly treated to makeit safe to the environment, the effluent still contains manyminerals which act as a fertilizer. Typically, the treatedeffluent from our sewer systems is discharged intowaterways. Similarly, when farmers use fertilizer on theircrops and fields, some will eventually be washed into creeksand rivers during rainy weather.

The result is that algae living in the waterways arestimulated to grow in over-abundance, often chokingwaterways and blocking light from other water plants.Later, great masses of algae die off and their decay uses upall the oxygen in the water, so that many fish and otherorganisms suffocate.

Introduction of Alien SpeciesThe European settlers to Australia brought many speciesfrom other places and released them into the newenvironment. The list includes plants such as prickly pear,lantana and bitou bush, and animals such as rabbits, foxes,pigs, camels, and cane toads.

All of these species, and many others, have become majorproblems in the ecosystems, because:

the aliens find themselves in an environment in whichthe normal predators and diseases are not present to keeptheir population in check

they are often more ruthlessly efficient in using resources,and so they out-compete the native species.

Many ecosystems around the world are being disrupted byalien species introduced by humans.

6. HUMAN IMPACTS ON ECOSYSTEMS

Toxin concentration = 1 unit

Toxin concentration = 10 units

Toxin concentration = 1000 units

Biological Magnification



19

AA LLOOCCAALLEECCOOSSYYSSTTEEMM

CONCEPT DIAGRAM (Mind Map) OF TOPICSome students find that memorizing the OUTLINE of a topic

helps them learn and remember the concepts and important facts.Practise on this blank version.



20

Practice QuestionsThese are not intended to be "HSC style" questions,but to challenge your basic knowledge andunderstanding of the topic, and remind you of whatyou NEED to know at the K.I.S.S. principle level.

When you have confidently mastered this level, it isstrongly recommended you work on questions frompast exam papers.

Part A Multiple Choice1. When studying an ecosystem, a transect study couldbe useful for recording the:A. abundance of species within the study area.B. distribution of species within the area.C. special adaptations of species to the habitat.D. food chains in the area.

2. Refer to the Transect Diagram of a rocky seashorehabitat on page 3.It would be reasonable to infer from this transect studythat:A. starfish eat kelp plants.B. blue periwinkles can withstand drying effects at lowtide better than starfish can.C. Crabs can survive the effects of wave action betterthan bubble weed.D. Kelp has special adaptations to resist drying out.

3. The best way to improve the accuracy and reliabilityof a quadrat study is to:A. use a bigger quadrat frame.B. deliberately drop quadrats where the targetspecies is found in larger numbers.C. measure the size of the study area more carefully.D. have more quadrat drops.

4. When using the capture-recapture technique,which of the following would be most likely to resultin an INACCURATE estimate of population size.A. The marking technique used reduces survivalchances of the animals.B. Increasing the number captured in the 2nd captureoperation.C. After release from the first cature, the animals mixrandomly back into the population.D. Increasing the number captured in the first captureoperation.

5. Which of the following is a biotic factor in anecosystem?A. Light intensity.B. Soil typeC. DiseasesD. Temperature range.

6. The streamlined shape of a dolphin is an adaptation to:A. the high buoyancy of water.B. low availablity of gases in the sea.C. the large temperature variations of aquatic habitats.D. the high viscosity of water.

7. Many seaweeds have brown or red pigments because:A. these absorb the predominately blue light thatpenetrates underwater.B. it camouflages them among the rocks of the sea floor.C. red and brown light penetrates water more than othercolours.D. this helps them control their temperature by absorbingmore heat.

8. The following graph shows the changes in populationnumbers for a prey species and 4 other species. Whichone (A, B, C or D) is most likely to be the predator?

9. The cleaner wrasse is a small fish of the coral reefwhich feeds on the parasites clinging to other fish. Manylarger fish will queue up to wait for a cleaner wrasse topick off their parasites.The relationship between the cleaner wrasse and thelarger fish is an example of:A. MutualismB. CommensalismC. AllelopathyD. Competition

10. Which of the following statements about ecosystemsis generally true?A. Energy is re-cycled, while chemicals have to beconstantly supplied.B. Both matter and energy are re-cycled.C. Matter is re-cycled, while energy has to be constantlysupplied.D. Both matter and energy have to be constantly supplied

11. The essential product of cellular respiration is:A. GlucoseB. OxygenC. Carbon DioxideD. ATP

Preyspecies

AB

CD

Time

ABUN

DANC

E



21

12. In the following food chain:algae limpet octopus fish sharkthe herbivore and the organism at the 4th Trophiclevel are respectively:A. limpet and sharkB. limpet and fishC. algae and fishD. algae and shark

13. Soil bacteria usually have the role in ecosystems of:A. DecomposersB. Disease causing parasitesC. Producer organismsD. Epiphytes

14. In a certain area, the biomass of several species is:Species Biomass (kg)

P 10,000Q 5,000,000R 100,000S 500

If these 4 organisms are involved in the same foodchain, then the order in the food chain is most likely:A. S > R > P > QB. P > Q > R > SC. Q > S > P > RD. Q > R > P > S

15. One of the adaptations visible in the NorthAmerican beaver is a large, broad, flat tail.

This adaptation probably helps the beaver survive by:A. giving it more stability and balance as it moves onland.B. helping it to carry the twigs and branches it feedson.C. used as a shield it protects against predator attack.D. helping it to swim and steer in water.

16. Eutrophication is when:A. polluting chemicals in the environment becomemore concentrated as they move up a food chain.B. aquatic habitats suffer from algal blooms due toover-fertilization.C. gases from burning of fossil fuels cause waterwaysto become very acidic.D. an introduced species over-populates an ecosystem.

Part B Longer Response QuestionsMark values given are suggestions only, and are to giveyou an idea of how detailed an answer is appropriate.

17. (4 marks) The following is a diagram of a transect done to studythe distribution of 4 plant species J, K, L and M in acertain area.

Describe the distribution of species K and L.

18. (3 marks) Using a capture-recapture method to estimate thepopulation of trout fish in a lake, the following resultswere obtained:1st capture: 537 trout tagged & released.2nd capture: 832 captured. Of these 45 were tagged.To the nearest 1 000, how many trout are in the lake?Show your working or reasoning.

19. (6 marks) To estimate the population size for a small plant speciesliving in a field, a quadrat study was carried out. The fieldwas rectangular, measuring 120m x 85m.

The quadrat used was a square wired frame 0.50m x 0.50m = 0.25 m2 area.It was dropped at random 10 times in the field. Thecount of the target species in each of the dropswas:- 8, 14, 2, 5, 9, 22, 3, 0, 12 and 7.

a) Calculatei) the area of the field.ii) the average number of plants per quadrat.

b) Find an estimate of the size of the plant population inthe field. Show working.c) Suggest one way to improve this study to give a moreaccurate estimate.

20. (4 marks) Construct a simple table and fill it in to compare theterrestrial and aquatic environments with respect toviscosity

buoyancytemperature variation

and availability of light

Pond

CreekKey

JJ KK LL MM

Verticalscaleexaggerated

Photo by Diana



22

21. (5 marks)a) Define the term mutualism.b) Give an example of mutualism, naming 2organisms and outlining how each is affected by therelationship.

22. (5 marks) In nature, allelopathy is a method of beating yourcompetition.Discuss this statement briefly, giving definitions andexamples as appropriate.

23. (8 marks) a) Write a word equation to summarize the process ofcellular respiration.b) The process makes energy available to living cells.

i) What is the original source of this energy?ii) How does the energy get into an

ecosystem?iii) In what form is the energy passed from organism to organism?

24. (5 marks) The following observations were made about thefeeding relationships in an Australian rural ecosystem.Use the information to construct a food web diagram.

Honey-eater birds feed on the nectar and pollen ofnative shrubs. These shrubs are also eaten by insectsand wallabies. Grass is eaten by insects, rabbits andwallabies, while mice feed on the grass seeds. Frogs eatinsects, while dingoes prey on rabbits and wallabies.Kookaburras hunt snakes and frogs. The snakes feedon frogs, mice and take the eggs and babies fromhoney-eater nests.

25. (8 marks) From your diagram for Q24 answer the following.a) Name three 2nd-order consumers.b) Name an organism which occupies more than onetrophic level.c) Write the longest food chain within this web.d) Name 2 organisms who could well be competitors.e) There is a world-wide trend of decline in amphibianpopulations. If the frog population in this food web wasdrastically reduced, what might happen to the:

i) insect population?ii) mouse population?

f) Comment on a human impact apparent from the foodweb for this ecosystem.

26. (4 marks) In a seaside rockpool, the total biomass of all visibleplants, herbivores and carnivores was estimated asfollows: Plants 10 kg

Hebivores 20 kgCarnivores 2 kg

a) On these figures alone, could the rockpool be a viable,stable ecosystem? Explain your answer.b) Over time, the rockpool community is studied and it isfound to be very stable and more-or-less unchanging.Suggest how this might be possible.

27. (4 marks)a) Explain what is meant by an adaptation.b) Give an example of an adaptation for each of thefollowing situations.i) A structural adaptation (in an animal) to a cold climate.ii) A plant adaptation to low light levels on the rain forestfloor.iii) An adaptation for water conservation in a desertanimal.

28. (3 marks) Outline a human impact on a named type of ecosystem.



23

Answer Section

Worksheet 1a) where b) interactingc) food d) hiding / escaping

f) transectg) straight line h) which species are presenti) Abundance j) quadratsk) average number / quadrat l) the environment / study aream) doing more quadrat drops n) Capture - Recaptureo) marking/tagging p) releaseq) capture r) marked/taggeds) total populationt) mixing randomly back into the populationQuadrat Study Problems1. Average per quadrat = 46 / 10 = 4.6Study area = 20 x 30 = 600 m2


= 4.6 x 600 / 0.25= 11,040

Population estimate = 11,000 starfish approx.

2. Average per quadrat = 105 / 20 = 5.25Paddock area = 300 x 400 = 120,000 m2


= 5.25 x 120,000 / 0.5= 1,260,000 weeds approx.

Capture - Recapture Problems1. Estimated = 1st capture x 2nd capture

Population no.marked in 2nd capture= 230 x 156

18= 1,993

Estimated population 2,000 lizards

2. Estimated = 1st capture x 2nd capturePopulation no.marked in 2nd capture

= 65 x 4812

= 260 possumsIf the possums enjoy being trapped then the recapture samplecontains a disproportionately HIGH number of tagged animals,who have come back to the traps deliberately. Mathematically, ifthe number 12 is too high, then the answer (260) is too low, sothe real population is higher than the estimate.

Worksheet 2

Biotic Factors Abiotic Factorsprey lightdiseases oxygenpredators waterfood plants soilcompetitors temperature

exposureacidity

a) terrestrial b) aquaticc) Viscosity d) low viscositye) higher viscosity f) streamlinedg) flotation h) morei) support j) much lessk) fur/fat/feathers l) sweatm) oxygen n) dissolveo) gills

p) conserve q) waterproofr) excretion s) osmosist) lose u) excretev) rainforests w) staghorns/orchids etcx) large/broad/packed with chlorophylly) colours / wavelengths z) Red/orangeaa) blue ab) pigmentsac) plants ad) dead materialae) chemosynthesis

Worksheet 3a) predator b) preyc) decrease d) more prey will be eatene) lower f) later / afterg) feeds h) killing iti) tapeworm j) ticks, mosquitoes, leechesk) commensalism l) remora (sucker fish)m) both gain a benefit n) bee & flowering plantso) bacteria / protozoa p) inhibit / slowq) allelopathy r) the same resource(s)s) one survives and thrives, the other declines.(one wins, one loses)

Worksheet 4a) re-cycled b) replaced / inputc) Sun d) plantse) photosynthesis f) food (glucose)g) growing, reproducing, responding etch) cellular respiration i) oxygenj) water & carbon dioxide k) ATPl) food chain m) producersn) consumers o) re-cyclep) inter-connect q) food webr) biomass s) herbivorest) pyramid

Worksheet 5a) adaptations b) insulates itc) streamlined d) viscositye) physiological f) sweatg) shiver h) smalli) concentrated j) conservek) behavioural l) sunbakem) shade / shelter

Practice Questions- AnswersPart A1. B 5. C 9. A 13. A2. B 6. D 10. C 14. D3. D 7. A 11. D 15. D4. A 8. C 12. B 16. B

Part B In some cases there may be more than one correctanswer. The following model answers are correctbut not necessarily perfect.

17. Species K is not widely distributed, but seems confined to thehilltop (higher elevation).Species L seems to occur only near water, on the banks of pondsand creeks.

18. Estimated = 1st capture x 2nd capturePopulation no.marked in 2nd capture

= 537 x 832 45

= 9,929

To nearest 1000, Estimate = 10,000 trout.

19. a) i) Area = length x width = 120 x 85 = 10,200 m2.ii) Average = (8+14+2+5+9+22+3+0+12+7) / 10

= 82 / 10= 8.2 plants / quadrat

b) Estimated = Average count x Study area Population per quadrat Quadrat area

= 8.2 x 10,200/0.25= 334,560

Estimate = 335,000 plants approximately

(Note: it is NOT appropriate to give an answer of 334,560since this suggests that the process will calculate the exactnumber of plants. It is a statistical estimate only, andanswers should be rounded off)

c) Make more drops of the quadrat.

20. Terrestrial AquaticEnvironment Environment

Viscosity low high

Buoyancy low high

Temp. variation high low

Light avail. good gets less with depth

21. a) Mutualism is a relationship between 2 differentspecies in which both gain a benefit.b) Honey bee and flowering plant.Bee gains food supply. Plant achieves pollination of itsflowers.



24

22. Competition is when 2 species both use the sameenvironmental resource, such as plants competing for thesame soil minerals in an area.Allelopathy is when one species produces a chemical ortoxin to inhibit the growth and development of otherspecies.Allelopathy is a method of dealing with competitors, suchas the lantana plant producing toxins in its roots, whichinhibits other plant species. This allows lantana to out-compete other plants and gain more soil minerals and light.

(Note: this is why lantana is such a noxious weed... its agreat competitor when introduced to a new environmentwithout its natural diseases and enemies.)

23.a) Glucose + Oxygen Carbon + Water + ATP

Dioxideb) i) The Sun

ii) Energy is captured by plants in photosynthesis.iii) As food (containing chemical potential energy)

24. kookaburras

snakesfrogs dingoes

honeyeaters insects mice wallabies rabbits

native shrubs grass

25 a) snakes, frogs, dingoesb) snake or kookaburrac) nat.shrubs > insects > frogs > snakes >kookaburrasd) wallabies and rabbits (best answer)

(Note: other possible answers are not as good.e.g. snakes & kookaburras both eat frogs, but kooks also eatthe snake, so they are not just competing for frogs.Honey-eaters and insects both eat shrubs, but differentparts of the plant, so not competing. Same with mice vrabbits... not eating the same parts of plants.)

e) i) without predators, the insect population shouldincrease.

ii) If less frogs, then snakes might eat more mice.Therefore mouse population may decrease.f) The rabbit is an alien species introduced to Australiafrom Europe. In the absence of its natural enemies anddiseases, it has over-populated at the expense of nativespecies.



25

26a) No. Stable ecosystems always have about 10 times morebiomass of plants than herbivores. The rockpool has lessplant biomass than herbivores. This is not sustainable.b) The biomass figures include only visible plants. Theremay be a large biomass of microscopic algae and planktonnot accounted for in the figures.or,Perhaps the herbivores in the rockpool are not just feedingon the plants present, but leave the pool at high tide to feedelsewhere.or,The community might be sustained by extra biomass whichwashes into the pool with waves and tides and feeds theherbivores.

27. a) An adaptation is a special feature of an organism,which helps it to survive in its environment.b) i) A thick fur coat, or feathers, or layers of blubber (fat)all act as heat insulators.

ii) Large, broad leaves capture what light is present.iii) Kidneys that produce small amounts of concentrated

urine, so less water is lost by excretion.

28. (many different answers possible)Humans clear forests, fill and drain wetlands etc foragriculture and to build towns, roads etc. This results inloss of habitat for many forest species which are adaptedto particular environments and cannot live elsewhere.

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