Years 7-8 Ecosystems Available Year 11-12 Science Courses Biology Preliminary Core Local Ecosystem...

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2

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Years 7-8 Topic 11 Ecosystemscopyright © 2008 keep it simple sciencewww.keepitsimplescience.com.au

3

“Mind-Map” Outline of TopicThis topic is a study of Ecology, which is a branch of Biology.

Ecology is a study of living things and their environment, with emphasis on how living things fit into the environment, and how they all interact with each other.

Seasonal

Predator &Prey

Competition

Decomposers

Photosynthesis&

Cellular Respiration

Ecosystems

Adaptationsto

Environment

Changes in

Population SizeEffects ofFire, Flood &

Drought

Producers&

Consumers

Food Chains&

Food Webs



4


Make your own “Mind-Map” TITLE PAGE.Cut out the boxes. Sort them into an appropriate lay-out on a page of your

workbook, then glue them down. Add connecting arrows and colour in.

Seasonal

Predator &Prey

Competition

Decomposers

Photosynthesis&


Ecosystems

Adaptationsto

Environment

Changes in

Population Size

Effects ofFire, Flood &

Drought

Producers&

Consumers

Food Chains&

Food Webs

Make your own “Mind-Map” TITLE PAGE.Cut out the boxes. Sort them into an appropriate lay-out on a page of your

workbook, then glue them down. Add connecting arrows and colour in.

Seasonal

Predator &Prey

Competition

Decomposers

Photosynthesis&


Ecosystems

Adaptationsto

Environment

Changes in

Population Size

Effects ofFire, Flood &

Drought

Producers&

Consumers

Food Chains&

Food Webs


5

EcologyEcology is the study of living things and their environment.Ecology studies the way living things depend on each other.

Ecology looks at the environment itself, and how living things fit into it.

What is an Ecosystem?An ecosystem can be as large or as small as you like. The whole Biosphere of theEarth is one ecosystem, or you might study just one little rockpool as an ecosystem.

One valley can be an ecosystem, or an entirecontinent... it just depends on how large, orsmall an area you want to study.

Every ecosystem is made up of 2 parts.



A co

ral r

eef e

cosy

stem

Living CommunityThe “community” is all the living thingswithin the ecosystem being studied. Allthe plants, animals and microbes arepart of the community.

They all depend on each other, andinteract with each other in manyimportant ways.

Non-Living EnvironmentAmount of Water

Amount of Light (e.g. for plants)

Amount of O2 and CO2 gases

Temperature Range

Soil Quality

All these things (and many more) canhave a huge effect on which plantsand animals can live in any particularecosystem.

For example, no plants can live in atotally dark cave, or the deep ocean,because there is no light forphotosynthesis.

Very few plants and animals cansurvive in a desert, or on an ice-capbecause of the extreme temperaturesand/or lack of water.

FoodLiving things eat

one another. Examples:• kangaroos eat grass.

• spiders eat insects.

Space & ShelterThey share living

spaces, and give eachother shelter.

Example:birds nest in trees.

SurvivalLiving things help

each other carry outvital processes.

Example:bees pollinate

flowering plants.

Parasites &Diseases

Some living things areparasites and feed fromothers without killingthem. Some microbes

cause infectiousdiseases.




6

AdaptationsIf you study any living thing in its natural environment, you will always find that

the plant or animal is well-suited to survive and live in that place.

It has special features which seem to help it “fit-in” to the place it lives.These special features are called “adaptations”.

We say it is adapted to its environment.

Some Examples of Adaptations

KookaburraGood Eyesighthelps it spot

insects, lizards, etc.

Large Beakhelps it catch and

kill its prey.

Featherskeep it warm, and are light-

weight for flight.

Colour Pattern isgood camouflage,so its prey do notnotice it waiting

in ambush.

Koala

Dense Furkeeps it warmon cold nights

and sheds waterin the rain.

Slow Moving, slow thinking, sleeps 20 hours a day.

This helps the koala survive ongum leaves which are a very

poor-qquality food.

Gum Tree Leavesare tough and water-proof to resist dryingout in dry weather.

They droopdownwards so theheat of midday is

avoided.

Rootsgo deep to find water.

Branchesare dropped indrought times,

so the tree needs less water.

(Don’t camp undergums in a drought!)

Clawsgive good gripfor climbing.

Kangaroo

Large Earsnot only help hearing, butact as radiators for cooling

down on a hot day.

Huge Legs & Feetallow for hopping, which is

a very efficient way to move around.

Powerful Tailacts as “3rd foot” when

standing, and is a counter-balance when hopping.

PlatypusWebbed Feet for swimming

“Duck-BBill”is very sensitive to detect worms,yabbies, etc in the mud or gravel.

Flat Tailfor steering

in water

Furtraps air next to its skin. This helpskeep it warm, even in cold water.




7

For each adaptation listed, suggesthow this might help survival.

You need to know the plant or animal’sway of life and normal habitat. This may

require some research and/or classdiscussion.

Worksheet 1Adaptations (2 pages) Student Name.............................................

Possum Sharp Claws

Tail that can grip

Large eyes

Excellent sense of smell

Nocturnal (Active at night)

Freshwater Crocodile

Webbed feet

Flattened, powerful tail

Long jaws with many sharp teeth

Eyes and nostrils on top of head

Sturt’s Desert PeaWide, shallow root system

Leaves are tough and waterproof

Seeds can survive in soil for decades

Can also reproduce from fast-ggrowing “runners” from stem

Wedge-Tail EagleGood eyesight

Powerful talons

Sharp, curved beak

Broad, soaring wings




8

Worksheet 1Adaptations (cont) Echidna

Powerful, sharp claws

Sharp spines cover body

Long snout and sticky tongue

Green Tree FrogGreen colour

“Suction-ppads on toes

Large mouth and sticky tongue

Large, powerful hind legs

Powerful claws

Female’s pouch opens backwards

Large, flat grinding teeth

Sleepy, docile nature(hint: it’s closest relative is the Koala)

Wombat

Stripes & spots colour pattern

Excellent sense of smell by “tasting the air”(with flickering, forked tongue)

Long, sharp claws

Goanna (rainforest species)

Can you think of otheradaptations that these

animals have?


9

Producers and ConsumersAll living things need food.

Food has chemical potential energy stored within it. When this energy is released, it powers all the life-functions... growth, movement, etc.

There are two main ways for a living thing to get food:

ProducersMake Food

from simple chemicals, and a source of energy.



ConsumersEat Food

that some other organism has already made.

Plants are ProducersIt is the plants that are the major producerorganisms in most ecosystems. (Some microbes make food too.)

Plants make their food by the process ofPhotosynthesis

What photosynthesis really does isabsorb energy from the Sun, and storeenergy in the food chemicals.

Luckily for us animals, the plants makemore food than they need. They storethe excess food in their fruits, leaves,roots and stems. We eat the plants or weeat other animals that ate plants.

The Producers (plants) make all the food on Earth.

They also make all the oxygen for us to breathe.

WATER + CARBON GLUCOSE + OXYGENDIOXIDE

cchhlloorroopphhyyllll

light energy

TThhee eenneerrggyy ooff lliigghhtt iissaabbssoorrbbeedd bbyy cchhlloorroopphhyyllll,,

tthhee ggrreeeenn ppiiggmmeenntt iinn tthhee cchhlloorrooppllaassttss

ooff ppllaanntt cceellllss

hhiigghh-eenneerrggyyssuuggaarr((ffoooodd))

ffrroommssooiill

ffrroommaaiirr

rreelleeaasseeddttoo aaiirr

Water & CO22are low-eenergy

chemicals

Animals are ConsumersAnimals are unable to make food. Theymust eat some high-energy food thathas been made by a producer, or theymust eat other animals that ate plants.

Once they get their food, they extract itsenergy to move, to grow, to reproduceand so on.

The process of extracting the energy from food is

Cellular RespirationGlucose + Oxygen Carbon + Water + Energy

Dioxide

Don’t forget that plants carry out cellularrespiration as well... not just animals.

You already know that CO2 and O2 areconstantly re-cycled between photosynthesisand cellular repiration.

The energy however, is NOT recycled.

It comes from the Sun, and is stored in food by theplants. Eventually either the plant, or an animal thatate it, uses the energy for some life function.

Energy cannot be destroyed, but once a living thinguses food, the energy becomes low-grade heatwhich is useless and cannot be re-used.

So the plants absorb more sunlight!

hhiigghh-eenneerrggyyssuuggaarrffrroommffoooodd

ffrroomm tthheeaaiirr

TThheessee aarree wwaasstteepprroodduuccttss

MMAAIINNPPRROODDUUCCTT




10

Food ChainsSince all the food on Earth is made by the plants (“producers”),and all animals (“consumers”) either eat plants, or each other,

the result is a “chain of feeding”... a Food Chain.

Food chains are the most basic relationships within an ecosystem.

Food chains are often described by a diagram like this:

The arrow shows the direction that food energy flows.NEVER DRAW THEM BACKWARDS!

Every food chain mustbegin with a plant

Grass Kangaroo Dingo

iiss eeaatteenn bbyy iiss eeaatteenn bbyy

The pattern of a food chain is always:

Producer Consumer 1 Consumer 2It can also be described as:

Plant Herbivore Carnivore(plant eater) (flesh eater)

Another Example

This food chain showsa number of

important points:

It doesn’t matter whichway the food chain

diagram is drawn, aslong as the arrows

point in the direction of energy flow.

There can be anynumber of living thingsin the chain, although it

is rare to have morethan about 6 steps.

Kookaburra

Lizard

Spider

Insect

Flower(plant)

Ocean Food ChainsOn land the food chains usually begin with afamiliar plant such as grass, or the leaves of atree or shrub.

In the oceans, mostfood chains begin withplankton. (the wordmeans “drifter”)

Plankton includesmicroscopic sea lifewhich drifts in the water.

The base of the food chains are single-celled“Phytoplankton” which have chlorophyll andmake food by photosynthesis. There may bemillions of them in each cup of seawater.

Feeding on them are the “Zooplankton”. Mostzooplankton are the tiny larval stages of jellyfish,crabs, barnacles, and so on. These in turn are eatenby shrimp-like krill, and these by fish, then biggerfish, then dolphins, etc. Many whales feed directlyon the krill, eating a tonne or more every day.

MMiiccrroossccooppiicc ddiiaattoomm,, aa uunniicceelllluullaarr pprroodduucceerr




11

Fill in the blank spaces

Plants are a)................................. of food.They make food by b)...............................using c)...................... and ........................,plus the energy of d)................................

All animals are e)................................ offood. This means they must eat foodthat f)..........................................................The result is that all animals eatg)..................., or other h)........................which have eaten plants.

All living things use the i)..........................from food to power all life processes. Toget this energy, they carry outj).......................................................

This process needs k)....................... gasfrom the air as well as l)......................from food. The waste products arem).............................. and ........................

A food chain describes the flow ofn)............................. through anecosystem. Arrows are used to show thedirection that the o)....................... flows.

Food chains always begin with ap)................... because they are theq)............................. which make all ther).......................

An animal that eats plants is called as)............................., and if it eats otheranimals it is a t).................................

Worksheet 2Producers, Consumers &

Food ChainsStudent Name.............................................

Each box names an organism, and states what it eats.Cut out all the boxes and re-arrange to form 4 different food chains.Glue down and add connecting arrows to complete each diagram.

Tree Leaves

Flowers

Grasshoppereats grass

Caterpillareats leaves of trees

Eagleeats Butcher Birds

Crabeats starfish

Starfisheats oysters

Oysterfeeds on plankton

Frogeats spiders

Spidereats butterflies

Butterflyeats nectar from

flowers

Snakeeats frogs

Octopuseats crabs

Butcher Birdeats caterpillars

Koo

kabu

rra

eats

liza

rds

Lizardeats grasshoppers

Plankton

Grass

Worksheet 3Food Chains

Student Name.............................................


12

The DecomposersAll living things produce wastes.

As well as their dung, there are dead leaves, shed fur, skin & feathers, etc.The amount of wastes and dead bits-and-pieces produced

each day in every ecosystem is enormous.

Luckily, in every ecosystem there are lots of garbage-disposal organisms who get rid of the waste materials.

Food Chain Including Decomposers

Are Decomposers the Same as Scavengers?

Bacteria & FungiIf you have studied the “Kingdoms ofLife” you may recall that bacteria aretiny, single-celled organisms.

Fungi includethings likemushrooms and“toadstools”. Thefamiliar “caps”shown in thephoto areactually just thereproductivestructures. Mostfungi grow in thesoil as a network of thin threads.

Most bacteria and fungi are decomposerorganisms. They feed on wastes anddead materials and cause it todecompose (rot) so that it is brokendown into simple chemicals.



Importance of DecomposersThe decomposers eat all the wastes andclean up the environment.

Their real importance is that bydecomposing the left-overs, theyre-cycle many chemicals that are

needed in the ecosystem.

Without the decomposers, the soilminerals such as nitrates and

phosphates would soon bedepleted. These “minerals” are

needed by plants for healthy growth.

The decomposers break-down thewastes and return essential chemicalsback into the soil. This way the plantscontinue to grow and make the food forall the food chains to continue.

Grass Kangaroo Dingo

Decomposers

WWaasstteess,, sshheedd ffuurr && sskkiinn

Simple chemicalsreturned to the soil

Deeaad leeaavees & staalks

Aren’t the decomposers doing the samejob as scavengers? e.g. vultures, whicheat dead remains.

No, there is a bigdifference.

A scavenger eats dead remains, but italso produces its own wastes, shedsskin, etc, etc. Scavengers do not causerotting, and they do not cause the re-cycling of soil minerals and othersimple, but important chemicals in theenvironment.Seashore Scavenger

DecomposersWorksheet 6




13

Food WebsAlthough we think in terms of food chains, this is really too simple.

Single food chains never exist by themselves in nature.In a real ecosystem, many different food chains inter-connect

with each other to form a Food Web.

For example, here is a food chain:

Plant Insect Spider Lizard Kookaburra

but this might be only part of all the feeding relationships occurring.

Kookaburras

Koalas

Snakes

Spiders

Blue-tongueLizards Goannas

Nectar-eating birdsPossums

ButterfliesGrasshopper

Grass Flowering Shrubs Trees

BeetlesFruit Flies

Frogs

The organisms shown in shaded boxes could be the food chain above.

Complicated?Even the food web shown is far toosimple for a real bush environment.

In a natural ecosystem there may behundreds of different species of insectsand spiders, dozens of types of lizardsand birds, and so on. We haven’tincluded insect eating birds andmammals, the bats, or the many types ofplants that are the basis of all the foodsupplies.

Weeds

Design of a Food Web Diagram

Because food webs get verycomplicated, it is important that thediagrams we use are well-organised.

Plants are usually placed at the bottom,in a line. As far as possible theherbivorous animals are placed in a lineabove the plants, and so on.


14

This diagram shows a food web thatmight exist in your back-yard.

Answer the questions1. According to this food web:a) what eats caterpillars?

....................................................................b) what do butcher birds eat?

....................................................................c) which animals are the “herbivores”?

....................................................................2. What is the reason (shown in thediagram) why many people like to haveblue-tongue lizards in their garden?

3. List all the “carnivores” shown.

Worksheet 4Food Webs Student Name.............................................

Producer OrganismsPhytoplankton, seaweeds.

HerbivoresZooplankton eat phytoplankton.Periwinkles (snails) and sea urchins eatseaweeds.

“Filter Feeders” (Collect plankton from the water. Therefore, they areeating both phytoplankton and zooplankton.)Barnacles, shrimp, mussels and tubeworms.

ScavengersCrabs eat dead scraps from barnacles,mussels and periwinkles.

Predators (hunter-killers)Octopus eat crabs, shrimp & sea urchinsStarfish eat mussels and periwinkles.

Hints• Start with plants in a line at the bottom.• Arrange herbivores in a line above that.• Continue working upwards.• Connect with arrows to show all

feeding relationships described.• It may be wise to do a “draft version”

on scrap paper first. From this you can see better lay-outs that will keep it neat and organised.

Worksheet 5Make a Food Web Student Name.............................................



Spiders

ButcherBird

Kookaburra

Weeds

Snails

SlugsInsects

Blue-TTongueLizard

Garden plants

Caterpillars

Here is information about some feeding relationships in a coastal rock pool.Your task is to construct a food web from this information.




15

Changes in Population SizeHumans are used to the idea that our population keeps rising.

This is NOT normal for animals and plants in nature.In natural ecosystems, the population of each species often goes

up and down with the seasons, or due to the impact of other species.

Seasonal ChangesIn the northern hemisphere (e.g. Nth America & Europe) the seasons are very

regular and predictable. Winter is harsh, but Spring always brings new plant growth, good food supplies and warm weather.

Population size always follows a yearly cycle.

Australia’s Climate is UnpredictableAustralia has seasons, but their effect is often less important than the

unpredictable “El Nino” events which cause severe droughts.Many Australian animals do not have a “breeding season”,

but produce babies whenever there is food and conditions are good.

SSpprriinn

gg

SSuumm

mmeerr

AAuuttuu

mmnn

WWiinn

tteerr

SSpprriinn

gg

SSuumm

mmeerr

AAuuttuu

mmnn

WWiinn

tteerr

SSpprriinn

gg

SSuumm

mmeerr

AAuuttuu

mmnn

WWiinn

tteerr

SSpprriinn

gg

SSuumm

mmeerr

AAuuttuu

mmnn

WWiinn

tteerr

SSpprriinn

gg

SSuumm

mmeerr

AAuuttuu

mmnn

WWiinn

tteerr

SSpprriinn

gg

SSuumm

mmeerr

AAuuttuu

mmnn

WWiinn

tteerr

Time (Seasons over 6 years)

Popu

latio

n Si

ze

Seasonal Population Change in a Temperate Climate

RRaappiidd iinnccrreeaassee eeaacchhSSpprriinngg bbrreeeeddiinngg sseeaassoonn

MMaannyy ddiieeiinn

WWiinntteerreevveerryyyyeeaarr

PPooppuullaattiioonn ddeecclliinneess eeaacchh yyeeaarr dduuee ttoopprreeddaattoorrss,, ddiisseeaassee aanndd oolldd aaggee..

0 10 20 30 40 50Time (years)

Popu

latio

n Si

ze

IInn ““ggoooodd””yyeeaarrss tthhee

ppooppuullaattiioonnkkeeeeppssrriissiinngg,,

eevveenn wwiitthhpprreeddaattoorrss,,ddiisseeaassee,,

eettcc

EEll NN

iinnoo

ddrroouu

gghhtt

EEll NN

iinnoo

ddrroouu

gghhtt

EEll NN

iinnoo

ddrroouu

gghhtt

EEll NN

iinnoo

ddrroouu

gghhtt

EEll NN

iinnoo

ddrroouu

gghhtt

PPooppuullaattiioonn ““ccrraasshheess””dduurriinngg ttiimmeess ooff

ddrroouugghhtt..MMaannyy ccoommpplleetteellyyssttoopp bbrreeeeddiinngg..

Annual CycleEach Spring the

population jumps asmany babies are born

at the same time.

Then the populationdecreases steadily as

some are killed bypredators or die of

various natural causes.

The death rate ishigher in Winter, so

population dropsfaster.

The dotted line shows the “yearly average” population. It goes up and down over anumber of years because of “good” and “bad” years.

Many Australian animals, suchas Red Kangaroos, will breedcontinuously in years when

there is plenty of food and water.The population grows largereven though many die from

disease, old age or predators.

When droughts occur thepopulation “crashes”. Breedingstops, and many die from lack

of food and water.

Once again, the graph shows“highs and lows”, but it is more

irregular, and the “cycle” is over many years.


16

Predator & Prey PopulationsSome population sizes are affected by another species.

The population of a predator is often dependent on the population of its main prey.Meanwhile, the prey species population is affected by the predator’s population.

CompetitionIf two species eat the same food, or need the same nesting sites (e.g. hollow logs)

or any other resource in the ecosystem, they must compete for survival.In nature this often results in a clear winner, and an extinct loser.

What HappensWhen the prey species population is high, thepredators can catch a lot of food.

The predators breed more successfully andraise bigger families because they have morefood. The predator population rises.

As the predators increase in numbers, they eat moreand more prey, so the prey population goes down.



CompetitionWhen 2 species need the same food (or otherresource) one species is always a little better atit than the other.

The “better” competitor’s population increases,while the other declines, and it may becomeextinct in that ecosystem.

Unfortunately, this is often what happens whenspecies are introduced to new ecosystems. Humanshave introduced many new species to Australia withdevastating results to some native species.

When the prey population gets low, thepredators have less food. They raise fewerbabies, and some starve to death.

Gradually, the predator population decreases.This means fewer prey get eaten, so theirpopulation begins to increase, and the wholecycle starts again.

Changes in Population SizeHumans are used to the idea that our population keeps rising.

This is NOT normal for animals and plants in nature.In natural ecosystems, the population of each species often goes

up and down with the seasons, or due to the impact of other species.

Time (over many years)

Aver

age

Popu

latio

n Si

ze

Predator-Prey Populations

PPooppuullaattiioonn““HHiigghhss””

PPooppuullaattiioonn““LLoowwss””

TThheerree aarree uussuuaallllyy mmoorreepprreeyy aanniimmaallss tthhaann

pprreeddaattoorrss

TThhee pprreeddaattoorr’’ss ““hhiigghhss””aanndd ““lloowwss”” aarree aallwwaayyssllaatteerr tthhaann tthhee pprreeyy’’ss..

Preyspecies

Predatorspecies

Time

Popu

latio

n Si

ze

SSppeecciieess ppooppuullaattiioonn ssttaabbllee

bbeeffoorree ccoommppeettiittiioonn

Extinct

PPooppuullaattiioonnddeecclliinnee

Poppuu

llatiion

iincre

asse

NNeeww ccoommppeettiittoorrssppeecciieess aarrrriivveess

iinn tthheeeeccoossyysstteemm

Typical Competition Graph

This graphhas been

“smoothed-out” to show

averagepopulationover many

years


17

Fill in the blank spaces

All living things produce a)......................materials. As well as their dung ordroppings, there are tonnes of deadb).......................... from plants, andc).......................... and .................... whichanimals lose or shed.

All this waste and dead matter is eatenby the d).................................. organisms,especially the e)................................ and.............................

As they eat this material they cause it tof).................................. (rot). This meansit is broken down into g).........................chemicals.

This is vital for h)................................ thesoil minerals which i)...................... needto be healthy. This allows the plants tocontinue to grow and make all thej)...................... for each ecosystem.

Decomposers are not the same ask)................................. which eat deadremains of other creatures. Theseproduce more l)..............................., anddo not cause material to rot and be re-cycled.

Worksheet 6Decomposers Student Name.............................................

1.a) Sketch on this grid (start at point A)a graph showing how the population ofan animal might change over a period ofyears, if it breeds in a regular cycle.

b) What causes the graph to go up?

c) What can cause it to go down?

d) Assume this is a prey animal. On the same grid sketch the graph of itsmain predator.

2. This graph below shows thepopulation of a species (“S”) whosenumbers have remained the same (moreor less) for thousands of years.

Then a new species (“X”) moves intothis ecosystem. The new species “X”eats exactly the same food as “S” does.

a) What do we call the relationshipbetween “S” and “X”?

b) Sketch on the graph the populationchanges to “S” and “X”, if the newspecies is better adapted and moresuccessful.

Worksheet 7Population Changes Student Name.............................................



TTiimmee ((yyeeaarrss))

PPooppuu

llaattiioo

nn SSii

zzee

A

TTiimmee ((mmaannyy yyeeaarrss))

SSppeecciieess ““XX””aarrrriivveess

““SS””

PPooppuu

llaattiioo

nn SSii

zzee


18

Fire, Flood & DroughtThe only certain thing about the Australian environment is that it is unpredictable!

Droughts can last for years, and then devastating floods arrive. Bushfires are common in most years and can cause widespread

damage to both human property and natural environments.

Effects on Australian Ecosystems

Fire: Destroy & Re-NewHumans see fire as a destroyer. To nativeAustralian ecosystems it is also a greatrenewing force.

Bushfires havebeen common inAustralia for ages.The aboriginalpeopledeliberately setfires forthousands ofyears beforeEuropeansettlement.

The ash from fire fertilizes the poor soils.Many plants are adapted to fire, and re-sprout quickly after a blaze. Many seedswill only grow after they are scorched byfire. Some Australian ecosystems canonly remain healthy by regular burning.



Flood: Flush & Re-ChargeFarmers know the value of flooding todeposit silt on the fields and replenish thetopsoil. A flood may destroy this year’scrop, but it helps guarantee future fertility.

In some natural ecosystems flooding isvitally important. In inland Australia, floodsre-fill the wetlands that vast numbers ofplants and animals live in and rely upon forsurvival.

Floods re-charge the underground watersupplies which emerge elsewhere as“springs” and feed the creeks, even in drytimes.

The salt lake ecosystems of CentralAustralia (e.g. Lake Eyre) cannot survivewithout the irregular flooding.

Many coastal estuaries need to be “flushedout” by flood water. Without a flood theestuary silts-up, closes up and becomes astagnant swamp instead of a healthybreeding area for fish and birds.Drought

Drought makes life very tough for farmers andfor rural communities, but most native plantsand animals are well adapted for long dryperiods. Many individuals may die, but thepopulations always recover.

Many Australian plantsproduce drought-resistantseeds which can survive fordecades, and sprout whenconditions improve manyyears later.

Most Australian mammalsare marsupials (pouched).This form of reproductionhelps drought survival.

When there is little food and water, the animalssimply stop reproducing. Many may die, buteven just a few survivors can rapidly re-growthe population after years of drought.

As well, many can surviveon very little water

because their bodysystems are adapted to

conserve water.

Many, like kangaroos, arehighly mobile so they can

move long distances tosearch for food and water

supplies.


19

Different ViewpointsA major ecological issue that has emerged in recent years concerns Australia’s

inland waterways, especially the Murray-Darling River System.

How Science Can HelpIt’s not up to scientists to make decisions to settle problems which

have social, political and economic implications. However, there’s plenty that Science can do to help.

A hundred years ago, paddlewheelsteam boats used to travel thousands ofkilometres up and down the DarlingRiver carrying wool, people andsupplies. The town of Bourke was amajor shipping port.

Today, the upper Darling River is just astring of shallow pools during mostyears. You’d be lucky to get to Bourkeby canoe, much less cargo boat.

The reasons for the change arecomplex, but certainly a major factor isthe extraction of river water forirrigation. So much water is taken fromthe river systems that there is notenough left to flow to the sea.

The Scientific View is that this is anecological disaster. The river ecosystemis dying. Plant and animal communitiesare severely threatened. The vast inlandwetlands are not being “re-charged” andmay be permanently destroyed unless“ecological flows” are re-established.

The Farmers’ View is radicallydifferent. The crops of rice and cottonthey grow provide income, not just fortheir families, but for the strugglingbush towns.

Their produce is worth many millions ofdollars to Australia’s export economy.To suddenly stop using water to irrigatethe crops would be an economic andsocial disaster. They want to put peoplebefore trees, birds and fish.

The Aboriginal Peoples’ View tendsto agree with the scientists, but fordifferent reasons. The Aborigines seethemselves as part of the land and havea responsibility to protect it and all itsinhabitants.

The Government View is that they musttry to find a compromise that works foreveryone. For most of our history theAborigines were ignored and the economyalways got its way. Modern governments heedthe Science, and must try to find ways to satisfyall the different groups of people.

New Crop VarietiesAustralia’s top research body, theCSIRO, has already helped develop andbreed new varieties of disease-resistantand drought-tolerant crop plants.

Further research may help developcrops that require less water so thatfarmers can get economical yields withless irrigation.

Ecological StudiesHow much water in the rivers isenough? Only by continuing to studythe plant and animal communities canwe be sure of what we’re doing and why.

Environmental ManagementOur National Parks systems aremanaged scientifically to preserveecosystems and provide places ofrefuge for native species.

By destroying introduced pest speciesand protecting remnants of wildernessareas, at least some of our naturalheritage is preserved for futuregenerations.

More and more Aboriginal people arebeing consulted and employed in thisrole. Their traditional methods are oftenmost effective at preserving andrepairing the natural environment.






20

Topic Test EcosystemsAnswer all questionsin the spaces provided.

1. (7 marks) True of False? T or Fa) Adaptations always help

survival in some way. ......b) The webbed feet of a platypus

help it grab its food. ......c) A predator is always a

herbivore. ......d) The energy in a food chain

comes from the Sun. ......e) Decomposers are the same

as scavengers. ......f) A food web contains many

food chains. ......g) The population graph for a predator

always “lags behind” the prey. ......

2. (3 marks)Humans think a bushfire is always adisaster. Is it always a bad thing fornatural ecosystems?

Explain your answer.

3. (5 marks)Match each description to an item fromthe list. To answer, write the letter (A,B,C,etc) of the list item beside thedescription.

Description matches with List Item

a) A special feature of a living thingwhich helps it survive. .............

b) Type of decomposerliving thing. .............

c) Producer organism for most ocean food chains. .............

d) Flesh-eater. .............

e) What food provides. .............

List Items Not all will be used. Some may be used more than once.

A. phytoplankton D. adaptationB. fungi E. energyC. herbivore F. carnivore

4. (5 marks) Unscramble these living things and drawa food chain diagram from them.

spider, snake, tree, insect, frog

Student Name............................................. Score = /20



octopus

crabs shrimp

musselstube worms

barnacles

periwinkleszooplankton

sea urchins

phytoplankton seaweeds

starfish


21

Answer SectionWorksheet 1Freshwater Croc.Webbed feet... swimming.Tail... power for swimming.Jaws & teeth... catching prey (fish).Eyes (etc) on top... allows it to see and breathewhile mostly submerged.

Desert PeaRoots... gather what little water might fall when itrains.Leaves... resist losing water.Seeds... can wait for the end of drought. Runners... can quickly reproduce whenconditions are good.

PossumClaws... climbing trees.Tail... helps in climbing, holding on.Eyes... see well in dim light.Smell... finding food eg fruit.Nocturnal... avoids predators which hunt by day.eg eagles.

W-T EagleEyes... spotting prey at long range.Talons... killing prey.Beak... tearing flesh.Wings... can glide & soar with little effort whilesearching for food.

G-T FrogColour... camouflage.Toes... helps in climbing, clinging.Mouth & tongue... catch & swallow insect prey.Legs... hopping, which is good to escape frompredators.

GoannaColour pattern... camouflage.Smell... can detect food at long range even whennot visible.Claws... tree climbing.

EchidnaClaws... breaking open termite nests.Spines... defence against predators.Snout, tongue... catching ants & termites.

WombatClaws... burrowing, digging roots (food).Pouch backward... pouch doesn’t fill with dirtwhen digging.Teeth... eating tough plant food.Dopey... can survive on poor quality food.

Worksheet 2a) producers b) photosynthesisc) CO2 & water d) sunlighte) consumersf) another organism has madeg) plants h) animalsi) energy j) cellular respirationk) oxygen l) glucosem) CO2 and water n) energyo) energy p) plantq) producers r) foods) herbivore t) carnivore

Worksheet 3Grass > grasshopper > lizard > kooka.

Flower > Butterfly > spider > frog > snake

Leaves > caterpillar > B.bird > eagle

Plankton >oyster > starfish > crab > octo

Worksheet 41.a) butcher birds & blue-tongue lizardsb) insects, spiders and caterpillarsc) insects, caterpillars, slugs & snails2.They eat garden “pests” such as slugs,snails & caterpillars3.spiders, butcher birds, b-t lizards,kookaburras

Worksheet 5



22

keep it simple science TM

Worksheet 6a) waste b) leavesc) skin, fur (etc) d) decomposere) fungi & bacteria f) decomposeg) simple, small h) re-cyclingi) plants j) foodk) scavengers l) wastes

Worksheet 71.

a) graph should go up and down.b) reproduction of youngc) death, because of predators, diseased) predators graph should be lower, andlater than first graph.

2. a) competitionb)

graph for S should decline, X should rise

Topic Test1.a) T b) F c) F d) Te) F f) T g) T

2.No. Bushfires are needed to keep somenatural ecosystems healthy. The ashes from fires fertilize poor soils,and some seeds can only sprout afterbeing scorched. Many Aust. plants are adapted to fire andquickly re-grow.

3.a) D b) B c) A d) F e) E

4.tree insect spider frog snake

(arrows must point correct way!)TTiimmee ((yyeeaarrss))

PPooppuu

llaattiioo

nn SSii

zzee

A

TTiimmee ((mmaannyy yyeeaarrss))

SSppeecciieess ““XX””aarrrriivveess

““SS””

PPooppuu

llaattiioo

nn SSii

zzee

lloowweerr aanndd llaatteerr

Years 7-8 Ecosystems Available Year 11-12 Science Courses Biology Preliminary Core Local Ecosystem...

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Transcript of Years 7-8 Ecosystems Available Year 11-12 Science Courses Biology Preliminary Core Local Ecosystem...