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Matter and energy
in ecosystems
The biosphere is made up of all the living things on the Earth. It depends on the hydrosphere
(the Earth’s waters), atmosphere (the Earth’s air) and lithosphere (the Earth’s crust and upper
mantle). Within it are regions called ecosystems, where living things strongly interact and are
interdependent. Ecosystems have a fine balance between organisms and their environments.
Human activities can greatly alter the biosphere, lithosphere, atmosphere and hydrosphere, and
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Components of ecosystems
3.1
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Ecosystems are not just made up of the plants and animals that live there, but also all the
microorganisms too small to see and all the non-living factors that make the conditions
of that environment. It is usually these abiotic factors that determine which organisms are
able to live in that environment. All the different individuals and different species within an
ecosystem interact with each other as well as with their environment. These interactions can
cause ecosystems to change.
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Students:
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»» recall that ecosystems consist of interdependent biotic communities and abiotic
components of their environment
»» outline how matter such as nitrogen, carbon and oxygen is cycled through ecosystems
»» describe how energy flows through ecosystems via food webs
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Changing populations
3.2
Students:
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Ecosystems are not static. The conditions are continually changing. Some changes are
regular, like night and day and the seasons, and some are extreme and unpredictable, like
bushfires and droughts. Other changes are caused by human intervention. Any change to
the conditions of an ecosystem will impact on the communities that live there. The study of
population in an ecosystem is called population dynamics.
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»» analyse how changes in biotic and abiotic components of an ecosystem affect populations
of organisms
»» evaluate some examples of strategies used to balance human activities and needs
in ecosystems
Managing sustainable
ecosystems
3.3
Human impact on ecosystems is necessary for us to obtain the resources we need to maintain
our standard of living. However, these impacts can be minimised where possible, and
managed to ensure ecosystems survive and flourish. Traditional land-management practises
are being reintroduced, and new modern practices are being created to conserve and protect
ecosystems.
Students:
»» research how Aboriginal and Torres Strait Islanders use their knowledge
to conserve and manage their environment
»» evaluate some examples of strategies used to balance human activities
and needs in ecosystems with conserving, protecting and maintaining
the quality and sustainability of the environment

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An ecosystem is a community of organisms (living things) and the
environment (surroundings). Rainforests, grasslands, freshwater lakes
and streams are all examples of ecosystems. Ecosystems have biotic
(living) parts – the organisms themselves and the relationships between
them, and abiotic (non-living) components – conditions and factors of
the habitat. Groups of organisms, often of many different species, live
together in communities. They share the same environment because they
all find food, shelter and other requirements there. Matter and energy are
transferred as a result of the different relationships.
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3.1
Components of ecosystems
Cycles of matter
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Each element takes part in natural cycles,
in which it moves through the biosphere.
The cycling of matter from the atmosphere
or the Earth’s crust and back again is called
a biogeochemical cycle (bio means living;
geo means earth). These biogeochemical
cycles break and make chemical bonds,
shuffling the elements around without
creating new atoms or destroying old ones.
Cycles of matter are examples of how living
and non-living things interact. The nitrogen
cycle and the carbon–oxygen cycle are
two important examples.
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All substances are made of matter. We
often use the term ‘organic’ to describe
the types of substances that make up
the biosphere. Organic material usually
contains the element carbon. Carbon
dioxide is an exception. While this molecule
clearly contains carbon, it is so small (only
3 atoms) that it does not behave chemically
like other organic molecules, and is
therefore considered to be inorganic.
In natural ecosystems, matter is neither
created nor destroyed. The amount of each
chemical element on Earth doesn’t increase
or decrease, but remains the same overall.
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Activity 3.1.1: Dynamic ecosystems
Ecosystems are constantly changing. Things enter the ecosystem, interact within it,
and move out again in a way that maintains a dynamic balance.
1 Working in a small group, identify some of the common resources all living things
require in an ecosystem. Use Figure 3.1 as a starting point.
2 Categorise the items in your list as either biotic (living) or abiotic (non-living)
resources.
3 Examine Figure 3.2. Identify as many processes as you can that naturally occur
within ecosystems. Make a list of inputs these processes require. Are these items
the same as the resources you listed in step 1? Why or why not?
4 Redraw Figure 3.2 using your examples of inputs and processes, then determine
what outputs would be produced by the processes you are discussing to complete
your flow chart.
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Ecosystems
Interactions between
organisms:
predation, symbiosis,
competition, etc.
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Temperature, soil,
composition,
light intensity,
wind speed,
etc.
Figure 3.1 Components of ecosystems.
Ecosystem
processes
Inputs
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Plant, animal and
microorganism
species
Environment
(abiotic)
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Community
(biotic)
Outputs
Nitrogen cycle
Nitrogen in the
atmosphere
Nitrogen-fixing
microbes
(in the soil)
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Nitrogen is found as a gas in the atmosphere
(N2). It is an incredibly stable chemical, and
comprises around 70% of our atmosphere.
Very few living organisms can actually use
the nitrogen found in the atmosphere, but
all living things need nitrogen as it makes
up substances such as proteins. Special
microorganisms called nitrogen fixers
change the nitrogen in the atmosphere
into a form we can use. Lightning can
also change some of the nitrogen in the
atmosphere. Denitrifying bacteria return
nitrogen to the atmosphere as nitrogen gas.
Nitrogen is absorbed from the soil by plants,
and then into animals that eat the plants.
When living things die, decomposers break
down the tissue of dead organisms and
return the nitrogen back into the soil again.
Nitrogen is often the substance that
limits the growth of living organisms. When
we farm, we tend to add extra nitrogen
into the soil in a form that plants can use
so they grow faster. For this reason, most
fertilisers are nitrogen-based. Using too
much nitrogen-containing fertiliser on
plant crops can cause nitrate to run off
from agricultural land into the waterways.
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Figure 3.2 The dynamic balance of ecosystems.
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Denitrifying
bacteria
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Animals
Decomposers
Plants
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Dead matter
Nitrites in
the soil
Nitrifying
bacteria
Nitrifying
bacteria
Figure 3.3 The nitrogen cycle.
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Ammonia in
the soil
Nitrates in
the soil
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Lightning
This excess of nutrients causes an effect
known as eutrophication, which results in
population explosions of microorganisms
known as blue–green algae or cyanobacteria
in the water – ‘algal blooms’. These blooms
then deplete the ecosystem of nutrients
required by different species, and also
decrease the oxygen level in the ecosystem
as the cyanobacteria decay. This often causes
the community to crash.
Figure 3.4 A ‘bloom’
of blue–green algae or
cyanobacteria in water
can be a sign of too much
nitrogen in the ecosystem.
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Carbon is found in the atmosphere as
carbon dioxide (CO2). Oxygen is present
in carbon dioxide and as the oxygen gas
we need to survive (O2). Carbon dioxide
moves into the air during a process in cells
called respiration, as well as through the
decomposition of organic material. The only
natural process that removes carbon dioxide
from the atmosphere is the photosynthesis
of plants. Scientists are now investigating
the effect of the increasing levels of carbon
dioxide in the atmosphere due to burning
of fossil fuels. Burning of forests is a double
threat to the amount of carbon dioxide in
the atmosphere: carbon stored within plant
tissues is released as carbon dioxide during
burning, and the loss of trees means less
photosynthesis to remove carbon dioxide
from the atmosphere.
Carbon and oxygen are found in places
other than the atmosphere. Figure 3.5
shows the cycling of carbon and oxygen in
the environment. They are changed and
used in different ways in the different parts
of the Earth. Table 3.1 shows how carbon
and oxygen move through different spheres
of the Earth: the atmosphere, biosphere,
lithosphere and hydrosphere.
As with nitrogen in the nitrogen cycle,
carbon and oxygen can become part of
different substances as they move through
the environment. However, the overall net
amount of each element does not change.
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Carbon–oxygen cycle
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Atmosphere CO2
Decomposition
Respiration
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Photosynthesis
Photosynthesis
Animals
Plants
Ocean
Soil organic matter
Marine deposits
Coal, oil and gas
Marble carbon sediments
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Respiration
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Fossil fuels
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Atmosphere O2
Earth’s crust
Figure 3.5 The carbon–oxygen cycle.
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Movement of carbon
Movement of oxygen
Found as carbon dioxide gas
(0.03%)
Released/produced by:
• burning fossil fuels
• respiration
• decomposing organisms
Used in:
• photosynthesis
Found as oxygen gas (21%)
Produced by:
• photosynthesis
Used in:
• respiration
• some decomposition
Also combines with carbon as
carbon dioxide (see ‘Movement of
carbon’)
Biosphere (living world)
Carbon dioxide used by plants in
photosynthesis to form sugars and
then other substances
Produced by photosynthesis
Used in respiration
Lithosphere (the Earth’s rocks and
soil)
Found in variety of forms in fossil
fuels, marine sediments, corals,
limestone, marble
Produced when living things
decompose to become sediments
that may change into fossil fuels
or sedimentary rocks
Released as compounds called
oxides when minerals are mined
Hydrosphere (the Earth’s waters)
Carbon dioxide from air can
dissolve in water to form weak
acid
Produced in photosynthesis, but
is not very soluble and may move
into atmosphere
Used in some respiration
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You have seen the importance of living
things in the nitrogen and carbon–
oxygen cycles. In the nitrogen cycle,
microorganisms ‘fix’ nitrogen into a form
our bodies can use. In the carbon–oxygen
cycle, plants absorb simple substances, such
as carbon dioxide and water, and convert
them into sugars by photosynthesis. Plants
make other compounds from the sugars
using minerals, and store them for further
use such as growth and reproduction.
Animals eating the plants have access to the
sugars and other compounds.
When plants and animals die,
decomposers (such as fungi and bacteria)
break down the dead matter to obtain
energy. Organisms do not absorb all the
matter eaten. For example, cellulose in plant
cell walls is not digested by some animals
and is passed through the body unused.
Decomposers act on this waste material.
Decomposers break down organic chemicals
into simple substances, which are released
into the atmosphere, surrounding soil and
water to be reused by plants, so continuing
the cycle.
Matter cycles can be easily disrupted by
significant changes in the communities of
living organisms that are a part of them.
Eutrophication is the result of excess
nitrogen in an ecosystem, leading to algal
blooms. Although excess nitrogen seems
like an advantage for the algae, the extreme
population densities strip most of the other
nutrients, specifically oxygen, from the
water. Long term, all aquatic organisms are
affected, as both the plants and animals that
require oxygen for cellular respiration need
to absorb it from the water.
The clear-felling of forests and woodland
to make way for grazing pastures has a
double effect on the carbon–oxygen cycle.
Less trees means less photosynthesis to
remove carbon dioxide from the atmosphere
and produce oxygen. High-density
populations of stock like cows or sheep
increase the amount of respiration, which
increases carbon dioxide production and
reduces the amount of available oxygen in
the atmosphere.
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Living things and the
cycles of matter
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Part of the Earth
Atmosphere
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Table 3.1 Carbon and oxygen in the environment.
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Deeper
u n d e r s ta n d i n g
Termites recycle carbon
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Plant cell walls are made of cellulose, a
complex carbohydrate that is insoluble
in water and does not break down easily.
Fungi break down cellulose and play a
major role in the decomposition of wood,
but fungi require a moist environment
and cannot survive in the arid areas
of Australia. In drier areas, such as
the savannah grasslands of northern
Australia, termites have a major role in
decomposing and recycling carbon and
other nutrients.
Termites are social insects that
live in nests. You may have seen the
massive termite mounds in Kakadu
National Park in the Northern Territory.
Termites also have microorganisms
that live in their gut, which break down
the cellulose of plant material such as
grasses, plants and wood. Scientists
have estimated that termites recycle
up to 20% of the carbon in ecosystems
such as the savannah grasslands.
Termites are not only responsible for
the increased soil fertility around their
mounds, but also provide food and even
nesting sites for many animals. They
are food for reduviid bugs (assassin
bug), dunnarts, numbats, lizards,
geckoes, skinks, bandicoots, echidnas
and bilbies. They provide shelter for
parrots, kingfishers, geckoes, pythons,
beetles and mice. A species of monitor
lizard even hijacks part of the mound to
incubate its eggs.
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Figure 3.6 (a) Termite mounds in Kakadu National Park
and (b) the termites that build and live within them.
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Questions 3.1.1: Cycles of matter
1 Recall the two ways nitrogen is converted into a form that can be used by living
things.
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2 Identify the only natural process that removes carbon dioxide from the atmosphere.
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3 Identify the two main processes of the carbon–oxygen cycle and describe how they
could be considered ‘opposites’.
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4 Describe some ways plants and bacteria contribute to the nitrogen and carbon–
oxygen cycles of matter.
5 Discuss ways in which humans have changed biogeochemical cycles.
6 Compare the ways that nitrogen and carbon enter the biosphere.
7 Explain the role of termites as decomposers in the savannah grasslands of
northern Australia. Why are they necessary?
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Energy in ecosystems
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Not all the energy
UNIVERSE
in ecosystems is
passed on. Some of
Solar energy
Biological systems
the energy is used by
living things (to do
work), and much of
the energy is lost to
Chemical energy
the atmosphere as
heat. Only 10% of
Heat energy
Matter is
the available energy
recycled
at each food chain
level is passed on to
the next level. Energy
cannot be created or destroyed (we say it is
Figure 3.7 Energy flow
conserved and transformed), but energy in a
through ecosystems and
the recycling of matter.
useable form is often lost. Energy moves and
changes in ecosystems, but unlike matter,
it is not recycled. Living systems must
continuously take in the Sun’s energy.
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All ecosystems rely on movement of
energy from one part to another. The first
source of energy in most ecosystems is
the Sun. However, only plants and other
photosynthetic organisms can use solar
energy directly. These types of organisms are
called autotrophs or producers. All animals
and some microorganisms cannot use the
Sun’s energy and must obtain their energy
through food they eat. Organisms that
require a source of food for their energy are
called heterotrophs or consumers.
Energy is passed through ecosystems
via food chains and food webs. Plants and
other photosynthetic organisms originally
harness solar energy. This energy is then
passed to the herbivores that eat the plants.
Carnivores obtain their energy from the
herbivores they eat, and so on.
Activity 3.1.2: Modelling energy transfers in the environment
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Energy can be difficult to imagine because it comes in so many different forms. Energy
can be transferred and transformed, but it cannot be created or destroyed. However,
many of the different forms of energy cannot be passed on through an ecosystem. This
activity demonstrates the proportions of energy that are used up by each step in the
food chain, that can be passed along or that are ‘lost’ in the form of heat.
What you need: 2 L bottle of coloured water, 10 mL and 100 mL measuring
cylinders, 4 plastic cups for each organism, dropper
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1 Work in groups of four to represent four different parts of the food chain: the
Sun, a native grass (producer), a cricket (herbivore) and a wedge-tailed eagle (top
consumer).
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2 Use the bottle of coloured water to represent the Sun’s energy. The total energy
available from the Sun is equal to the volume in the bottle (2000 mL).
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3 Give a cup to each person representing a part of the food chain.
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4 The plant receives, through photosynthesis, 3% of the solar energy available to
it: 3% of 2000 mL = 60 mL. Measure and pour 60 mL of coloured water into the
plant’s cup.
5 The herbivore receives 10% of the energy: 10% of 60 mL = 6 mL. Measure out 6 mL
from the plant’s cup and pour this into the herbivore’s cup.
6 The top consumer receives 10% of this energy: 10% of 6 mL = 0.6 mL. Use the
dropper to take out about 0.6 mL from the herbivore’s cup and pour this into the top
consumer’s cup.
• Explain why are there fewer top consumers in an ecosystem than herbivores.
• Explain what has happened to the 1940 mL of ‘energy’ from the Sun that did not
pass into the plant.
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Energy for work
When we need a quick boost of energy, we often choose sugary foods to eat. Although sugars
contain energy locked in the bonds of their molecules, this energy cannot be used directly by
organisms. They must first convert it into other forms.
Many energy transformations keep a living organism alive, functioning and carrying out
chemical reactions that keep cells working. We can describe these processes as the work of living
organisms. Some of the types of ‘work’ performed by living organisms are shown in Table 3.2.
Table 3.2 The ‘work’ of living organisms.
Examples
Building compounds
All organisms use energy to build and replicate molecules, such as
lipids (fats), DNA (deoxyribonucleic acid), RNA (ribonucleic acid) and
proteins, so they can manage metabolic processes, grow and pass
information on to offspring.
Communication inside an
organism
Energy is needed for communication within and between cells. Electrical
energy and chemical energy are used when nerves transmit information
throughout the body, or when hormones are produced
Physical movement
Energy is supplied for voluntary movement, such as movement of leg or
arm muscles, or for involuntary movement, such as contraction of the
heart or movement of plants towards sunlight.
Transport
Energy is required to move substances, such as nutrients and wastes,
throughout an organism’s body.
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Type of work
Photosynthesis
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Photosynthesis rate
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0.8
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Figure 3.9 The rate of
oxygen produced during
photosynthesis is affected
by the intensity of light.
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Light intensity
All living things need energy to grow,
reproduce and repair, defend themselves
and to move. Plants, some algae and some
bacteria are able to gain this energy during
photosynthesis. In this process, glucose is
synthesised (made) from water and carbon
dioxide. This requires light energy and
the presence of an organic catalyst called
chlorophyll, which is found in cellular
organelles called chloroplasts. Chloroplasts
are concentrated in the cells of plant
leaves. Stomata in the leaves are tiny pores
through which the carbon dioxide needed
for photosynthesis enters and the oxygen
exits (see Figure 3.8). The solar energy
is converted into chemical energy in the
bonds of glucose. The overall equation for
photosynthesis is:
carbon dioxide + water → glucose +
oxygen
6CO2 + 6H2O → C6H12O6 + 6O2
Figure 3.8 The stomata of a plant (seen here under a
microscope) are opened and closed by guard cells to
allow the gas exchange of oxygen and carbon dioxide.
Photosynthesis produces oxygen
and removes carbon dioxide from the
atmosphere. The glucose product is soluble
and readily transported around the plant.
Any extra glucose can be converted into
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Experiment 3.1.1: Starch production and light
Aim
To find out whether light is necessary for the production of starch in leaves.
Hypothesis
Construct an ‘If … then …’ statement that predicts the effect of light on the production
of starch in leaves.
Materials
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4 Petri dishes
Methylated spirits
Iodine solution
Aluminium foil
Paper towel
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>> Methylated spirits is highly flammable and must not be heated using a naked
flame.
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WARNING
• 4 soft-leaved plants (such as
geraniums) of the same size, shape
and colour, in seedling pots
• Hotplate and water bath
• Beakers (250 mL)
• Tongs
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Method
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1 Label two plants A and two plants B. Place them in a dark cupboard for two days.
(This is to ensure that no starch is present in the leaves. You should be able to
verify this at step 6 – there should be no change in the colour of iodine.)
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2 Break off one leaf from each plant. Place leaves from the A plants in one beaker,
add water and boil for several minutes (leaves should become soft). Repeat with
the leaves from the B plants.
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3 Place the A leaves in a new labelled beaker containing methylated spirits, and
place the beaker carefully in a water bath. Leave them for 5 minutes or until the
chlorophyll has been removed from the leaf.
4 Remove the leaves with tongs, rinse with water and pat dry with paper towel.
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5 Place the leaves in a Petri dish and add 2–5 drops of iodine solution, just enough to
cover the leaf.
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6 Observe any colour change and record your observations.
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7 Repeat steps 3–6 with the B leaves.
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8 Repeat step 1, then place aluminium foil over the leaves of the two A plants and
place all plants in sunlight for several days.
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9 Complete steps 2–7, ensuring you test the foil-covered A plant leaves.
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Results
Include your observations in a table.
Discussion
1 Which plants, A or B, were the control group?
2 Identify the dependent variable.
3 Identify some controlled variables.
4 Explain why a positive test for starch is considered an indication that
photosynthesis has occurred.
5 Is this experiment quantitative or qualitative? Explain your answer.
6 Suggest a change to improve the method if you were to repeat this experiment.
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Student Design Task
Understanding photosynthesis
Choose one of the following questions and then design and conduct your own
experiment.
1 Is chlorophyll necessary for photosynthesis?
2 Do increased levels of carbon dioxide increase the rate of photosynthesis?
Questioning and predicting
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Consider the question you have chosen to investigate. Write some ‘what if’ questions
related to your topic. Make a prediction about each of your questions. Convert your
questions and predictions into ‘If … then …’ hypotheses.
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Planning investigations
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Identify the experimental variable for your experiment. Consider all other variables
that may affect your results and how you will control these. Write a clear, step-by-step
method for your experimental procedure.
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Here are some ideas to help you:
• Variegated leaves with green and cream patches contain areas where chlorophyll is
present and patches where it is absent.
• You may need to grow plants in a sealed, controlled atmosphere. One way is to grow
the aquatic plant Elodea in a beaker of water. Place the Elodea under an inverted
filter funnel that has been sealed from the air (by inverting a test tube full of water
over the top). The bubbles of oxygen released by the plant will rise up through
the funnel into the top of the test tube, displacing water and indicating the rate of
oxygen production.
• Plants release oxygen as a result of photosynthesis, and this can be seen as
bubbles around the leaves of aquatic plants.
• Carbon dioxide is released in some chemical reactions or is released by respiring
animals. Some antacid tablets, such as Alka-Seltzer, release carbon dioxide when
added to water.
Conducting investigations
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Discuss your method with your teacher and get their approval. Revise your method if
required. Then, carry out your experiment according to your method.
Processing and analysing data and information
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Record all observations and determine if there are any trends (patterns) or cause-andeffect relationships. Is your data qualitative or quantitative?
Problem solving
What problems did you encounter during your experiment? Was there a problem with
your method? Did something unexpected happen? Suggest ways to improve or extend
your experiment with further testing.
Communicating
Present your findings as a formal scientific report.
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C6H12O6 + 6O2
→ 6CO2 + 6H2O + ATP
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glucose + oxygen → carbon
dioxide + water + energy
Stored chemical energy (ATP) is released
as required for cellular work, but the release
is much slower and more controlled than
burning fuels such as wood.
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Whenever we burn a fuel, such as wood or
oil, we release energy that has been chemically
stored in the molecules. Burning requires
oxygen and is a very rapid process, producing
a lot of heat energy, carbon dioxide and water.
In living organisms, sugars such as
glucose contain energy, but it is not directly
useable. If all the energy stored in the bonds
of glucose were released at once, the rapidly
produced heat would be more than enough
to cook the cells of living thing. Energy
from the breakdown of glucose must first be
transferred to a molecule called adenosine
triphosphate (ATP) before it can be used
in cells. This occurs in organelles called
mitochondria in a process called cellular
respiration. ATP contains energy that is
directly useable by cells.
Oxygen is used when it combines
with glucose during cellular respiration.
As well as glucose, fats and proteins can
be used to produce ATP. The energy stored
in the chemical bonds of glucose (C6H12O6)
is transferred slowly into ATP. Carbon
dioxide and water are waste products.
The overall equation for cellular
respiration is:
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Cellular respiration
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Figure 3.10 ATP (adenosine triphosphate) molecules are the energy currency of organisms.
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Photosynthesis and respiration: ‘opposite’ reactions
Sun
ECOSYSTEM
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Light energy
Glucose
Respiration
Energy
for plant cells
Energy for
animal cells
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stored or changed
into other useful
Figure 3.11 Energy is transferred from (a) light to plant cells and (b) from
organic substances
Heat energy
Figure 3.12 Energy flows into an ecosystem as sunlight. Plants
trap this energy in the chemical bonds of matter such as
glucose. The glucose, produced during photosynthesis, is used
in respiration.
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plants to animals.
Glucose
and oxygen
is the energy source for most cellular activities
TE
Respiration
Glucose
EC
Digestion
Cellular respiration
in mitochondria
ATP
D
stored or changed
into other useful
organic substances
Plant
Photosynthesis
in chloroplasts
PA
Photosynthesis
G
E
CO2 + H2O
Chlorophyll
in plants
FS
Photosynthesis and respiration are effectively the opposite of each other. Photosynthesis
traps energy from the Sun into chemical bonds, such as those of glucose. Respiration
moves the energy out of glucose, where it can be accessed directly by cells. However, the
chemical equations listed here are only summaries of the processes. Both photosynthesis
and respiration are actually a series of smaller reactions that involve many more compounds
than those in the summary equations. These processes are not reversible because respiration
and photosynthesis require their own specific enzymes to catalyse the reaction in one
direction. But the net result of this pair of processes is to undo the other.
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Deeper
u n d e r s ta n d i n g
diversity are also shown. All ecosystems
were originally natural ecosystems, and
some of them have been changed into
agricultural and urban ecosystems.
Comparing ecosystems
Table 3.3 shows the energy and matter
inputs and outputs of three types of
ecosystems. Their complexity, stability and
Table 3.3 Comparison of urban, agricultural and natural ecosystems.
Complexity
and stability
Mainly fossil
fuels, nuclear,
hydroelectric
Excessive burning Little
with rapid heat
output
Little; humans
dominate
Simple;
unstable:
imbalance of
animals over
plants
Agricultural
Mainly light and
fossil fuels
Mainly
photosynthesis
and respiration
with gradual heat
output
Some
Little; single
crop species
or animals
dominate
(monoculture)
Simple;
unstable
Natural
Light
Mainly
photosynthesis
and respiration
with gradual heat
output
Nearly all
High
Complex;
relatively stable
PA
Questions 3.1.2: Energy in ecosystems
FS
Diversity
O
Urban
Matter
recycling
PR
O
Energy use
E
Energy input
G
Ecosystem
Remember
1 Outline the difference between energy and matter.
D
2 Outline the differences between a flow of energy and a cycle of matter in an
ecosystem.
TE
3 Identify some uses of energy in the bodies of living organisms.
4 Identify the source of energy for cellular respiration.
EC
5 Write a general equation for cellular respiration.
R
Apply
6 Explain why cellular respiration constantly occurs in cells.
R
7 Identify the raw materials needed for photosynthesis. Explain how they enter a
plant.
C
O
8 Explain why it is fair to say that photosynthesis is essential to the functioning of
almost all ecosystems.
U
N
9 Outline how cellular respiration and photosynthesis are related.
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Relationships in ecosystems
Collaboration
FS
Collaboration occurs when organisms
cooperate with each other to ensure their
survival. This usually occurs in species that
exist in large populations.
Examples include:
• ants – leaving a scent trail when they
search for food so other ants can find the
food too
O
• wolves – hunting in packs
PR
O
• sea lions – leaving pups in crèches to be
looked after while they go hunting
E
• flowering plants – growing close together
to increase the chances of crosspollination
• fish – swimming in large schools help
confuse predators and avoid being eaten.
PA
G
A community and the relationships
between individuals in the community
make up the biotic part of an ecosystem. In
every community you will find producers,
herbivores, carnivores and decomposers.
Complex interactions happen between these
living things. Predators hunt for their food,
herbivores keep an eye out for carnivores
to avoid being eaten, and decomposers
slowly break down dead plants and
animals. Organisms compete within their
own species and with other species in the
community for food and other resources.
Although some organisms do not
have any direct effect on each other in an
ecosystem, most organisms have some kind
of relationship. These relationships may be
beneficial, neutral or detrimental (harmful),
and they may be ongoing or short-lived.
Relationships may be between organisms of
the same or different species.
TE
D
Relationships within a
species
R
R
EC
Mating between same-species partners
produces viable offspring, thus ensuring
the survival of the species. All sexually
reproducing species must come together at
U
N
C
O
Figure 3.13 The fish in
this school swim together
to make it harder for
the shark to single out
individuals to eat.
Intraspecific (intra meaning within;
specific meaning species) relationships
exist between individuals of the same
species, usually of the same population.
There are three main types of intraspecific
relationships.
Mating
Figure 3.14 The female seahorse lays her eggs
inside the male’s pouch where he fertilises them and
carries them until they are ready to hatch.
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some stage in their life cycle. Some species
may live in large groups of males and
females, like antelope. In other species, like
orang-utans, the genders live separately
until breeding season. The young usually
stay with their mother until they are old
enough to fend for themselves. Many plants
sexually reproduce, but often need the help
of the wind or a pollinator to bring the
pollen (sperm) to the ovum (egg).
• predators like lions compete over food
U
N
C
O
R
R
EC
• birds compete over nest sites.
FS
O
PR
O
E
Figure 3.17 Symbiosis: A
lichen is an alga and a fungus,
although you cannot see the
two organisms separately
(except under a microscope).
The alga photosynthesises
and the fungus supports the
alga and provides it with other
nutrients.
Beneficial or neutral
relationships
Mutualism, symbiosis and commensalism
are examples of relationships between
different species. Mutualism is a
relationship between two organisms
in which both organisms benefit. A
relationship between two species that are so
interdependent that neither can survive
without the other is called symbiotic.
Lichen is an example of a symbiotic
relationship, whereas the anemone and
anemone fish is an example of only
mutualism. Mutualistic and symbiotic
relationships tend to last a long time, often
a lifetime. These relationships have driven
adaptation to better suit the other species.
For example, flowers have evolved to take
on particular colours and shapes, and to
produce specific scents and nectars, to better
attract specific pollinators.
Commensalism is a relationship in
which one organism benefits and the other
organism is not affected. Commensalism
is relatively rare in the natural world – it is
unlikely an organism that has a relationship
with another will not be affected in some way.
TE
• males compete for the right to mate with
females
Interspecific (inter meaning between)
relationships exist between individuals
or populations of different species.
These relationships can be beneficial or
detrimental to one or both species involved.
G
Examples include:
• seedlings from the same plant species
compete with each other for light and
space as they grow
Relationships between
different species
PA
Competition occurs when organisms use
the same limited resource. Organisms will
compete for all possible resources if there is
not enough for everyone. Individuals that
are good competitors will get more of the
resource than weaker competitors. Those
that do not gain enough of that resource
may die.
D
Competition
Figure 3.16 Mutualism: The anemone fish hides
within the tentacles of the sea anemone, where it is
camouflaged from its predators. The sea anemone is
cleaned of algae and parasites by the fish.
Figure 3.15 The two male bison are competing to
mate with females.
Figure 3.18 Commensalism:
Sometimes herbivorous
animals, such as cattle and
water buffalo, flush insects out
of the grass as they wander
through. Birds, such as cattle
egrets, feast on the insects and
therefore benefit. However, the
cattle are unaffected by this
relationship.
Figure 3.19 Commensalism:
Certain plants rely on
passing animals to disperse
their seeds. The seeds
have tiny hooks to attach to
overmatter
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Detrimental relationships
FS
O
Number of prey
Number of predators
Prey
PR
O
Figure 3.22 Parasitism:
Ticks attach to the skin of
animals and slowly drink
their blood. Bacteria from
the digestive system of the
tick can infect the animals.
Predator–prey, parasitism and competition are relationships in which at least one of the
species has the potential to be greatly harmed.
In a predator–prey relationship, the predator organism eats the prey organism.
Therefore the predator benefits and the prey is harmed. The predator–prey relationship is
not long-term and only happens when a predator has the opportunity. Predators and their
prey have a balanced relationship with each other. If all the prey is eaten then the predator is
disadvantaged. Figure 3.20 shows a typical graph of predator–prey population fluctuations.
Predator
G
Figure 3.21 The eagle is the predator and the fish has
definitely been harmed!
PA
EC
TE
D
Parasitism is a relationship in which
one organism (the parasite) lives in or on
the body of another (the host). The parasite
benefits and the host is harmed to varying
degrees. A good parasite can survive and
reproduce inside its host for close to the
normal life span of the host. However, if the
parasite takes too many nutrients from the
host, the host may get sick or even die. If the
parasite cannot leave the host in time, they
too will die.
Competition may exist between
members of different species that share a
resource such as food or nesting sites. Many
different animals nest in tree hollows. The
removal of dead trees reduces the number of
nesting sites and increases the competition
for them. Without adequate shelter, many
animals cannot reproduce or survive.
Inhibition, or allelopathy, is a particular
type of competition that occurs when
one organism produces a chemical that
directly inhibits or hinders the growth and
development of another. This is commonly
seen in plants and microorganisms.
N
C
O
R
R
Figure 3.23 Parasitism:
Hookworms attach
themselves to the inner
lining of the human
intestine, feeding on
nutrients as they pass by.
The host will often lose
weight from lack of food.
If the host doesn’t eat
enough, the worm has
been known to burrow out
of the intestines and travel
to other organs, where
real damage can be done.
Figure 3.20 A predator–prey graph. The scales aren’t
shown but the prey numbers are mostly greater
than those of the predators. Notice the increase and
decrease in prey numbers usually comes before the
increase and decrease in predator numbers.
E
Time
U
Figure 3.24 Competition:
A black periwinkle (Nerita)
competes for food with
the limpet (Cellana) on a
rock platform – both feed
on algae growing on the
rocks. The periwinkle
moves faster but feeds
less efficiently than the
limpet, so both can survive
as the periwinkles usually
leave behind some algae
for the limpets. However,
when the periwinkles
are removed, the limpet
population increases.
Figure 3.25 Inhibition: Penicillium is a fungus that
produces penicillin, an antibiotic that inhibits the
growth of many species of bacteria.
Figure 3.26 Inhibition: The Lantana plant, an
introduced species in Australia, releases a chemical
in the soil that inhibits the growth of native plant
species.
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Experiment 3.1.2: Observing competition
Aim
To identify some factors that affect competition in germinating seeds.
Materials
Packets of seeds (a variety of vegetables or flowers is needed)
Small plot (20 × 20 cm) in a garden, divided into thirds (alternatively, 3 mediumsized pots containing good-quality potting mix)
Measuring cylinder or graduated jug for watering
O
Method
FS
Hypothesis
Use your knowledge of the resources required by plants to write an ‘If … then …’
statement to predict the outcome of this experiment.
PR
O
1 Prepare the plots so the soil is moderately deep and smooth. Label them A, B and
C.
2 In A, densely scatter the seeds of one type (for example, only radish seeds).
3 In B, plant six seeds of the same type as for step 2, but spread evenly apart.
4 In C, densely scatter a variety of seeds.
E
5 Water the soil each day as evenly as possible with the same amount of water.
PA
G
6 Record the growth of the seeds. If possible, take photographs each week or every
few days when the seeds begin to germinate. If the seeds become seedlings (small
plants), their heights may be measured and recorded in a table.
TE
D
Results
Record all results. You could take photos showing the progress of growth and/or
record the average heights of plants of different species and record them in a table.
Discussion
EC
1 What assumptions did you make when drawing a conclusion?
2 How could you have improved the validity and reliability of this experiment?
R
3 What would be your advice to another student who wants to perform the
experiment?
R
4 Was there evidence of competition between the seeds as they germinated? Explain
using your results.
O
5 Are there other factors that might affect the growth of seeds?
C
6 If you were to complete this experiment again, how would you improve or extend it?
N
7 Have you previously observed competition between organisms in the natural
environment? If so, describe it.
U
Conclusion
Write a conclusion regarding the factors that affect competition between germinating
seeds.
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Activity 3.1.3: Pollination – the benefits are mutual
The pollination of flowering plants by animals and other agents has contributed to
the great success of these plants and their dominance in many parts of the Earth. In
return, a diverse range of insects, mammals and birds benefit from ‘rewards’ offered
by flowering plants.
What you need: computer with access to the Internet, printer, paper, pens and pencils
Perform this exercise as a small-group activity and produce a single report as a group.
• the grouping of pollinators into different types
O
• advantages of pollination to the pollinator and to the plant
FS
1 Research examples of the pollination of flowering plants on the Internet. A good
place to start is the Plant2pollinator resource in the Australian Museum website’s
‘Bugwise for Schools’ section. Items to consider include:
PR
O
• patterns in pollination, for example, grasses and cereal crops of the world (they
are flowering plants – how are they pollinated?)
2 Takes notes about the information you think is important. Remember to write
the full reference for each of your sources of information, and to summarise and
paraphrase.
E
3 Analyse the information and process it into a short report on pollination with
examples, photographs and diagrams.
PA
G
4 Share your group’s report with another group or discuss as a class.
A dynamic balance
O
R
R
EC
TE
D
All organisms live in a complex web of
interrelationships – with each other
and with their environment. Many of
these relationships are between living
things, as you have seen. Non-living
(abiotic) factors play a critical role in
determining what type of community
survives at a particular place.
Abiotic factors include the physical
and chemical parts of the environment.
Abiotic factors in terrestrial (land-based)
ecosystems are different from those factors in
aquatic (water-based) ecosystems. Sunlight,
temperature, rainfall and soil type are all
examples of physical factors. Chemical factors
include availability of minerals, oxygen and
carbon dioxide, and soil or water pH and
salinity. Ecosystems in New South Wales
include arid grasslands, rainforests, rock
platforms, mangroves, salt marshes, sand
dunes, freshwater lakes, mallees and alpine
herbfields. Some people distinguish natural
ecosystems from agricultural and urban
ecosystems, which are dominated by people.
A group of organisms of the same species
U
N
C
Figure 3.27 Pollination
involves the transfer
of pollen from the
male parts of flowers
to the female parts of
other flowers of the
same species. Animal
pollinators, such as
bees, small mammals or
birds, visit the flowers for
food such as nectar. The
pollinators then transfer
the pollen when they visit
other flowers. Pollen may
also be carried by wind or
water.
living in the same ecosystem is called a
population. An ecosystem needs to be able
to maintain a balance so all species can exist
at their optimum population size. Gains due
to reproduction and immigration (moving
in) must balance the losses due to death and
emigration (moving out). Changes in one
species’ population can dramatically affect
the population of a different species.
Consider the food web for the ecosystem
shown in Figure 3.28. Frog numbers have
decreased in parts of Australia for reasons
still being researched. If frogs decreased in
this particular ecosystem, consequences
could include:
• an increase in grasshoppers and thus a
loss of grass
• an increase in praying mantises
• a decrease in lizards
• a diversion of birds towards a diet of
praying mantises rather than frogs and
lizards
• a consequent decrease in praying
mantises
• a further increase in grasshoppers and
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more loss of grass – if this was severe
enough the ecosystem would be at risk as
it depends on a good supply of grass.
Praying mantis
Grasshopper
Frog
Figure 3.28 Changes to
the frog population will
affect all other species in
the food web.
O
naturally but they may be intensified
by factors such as floods and bushfires.
Reproduction, death, migration, natural
Lizard
FS
Grass
Bird
overmatter
PR
O
The most likely outcome is that the bird
population would decrease so all species
would return to balance with reduced
population sizes. A positive effect is that
it might enable the frog population to recover.
Ecosystem balance is a type of dynamic
equilibrium (dynamic means changing;
equilibrium means balance). Changes
may upset the equilibrium but another
equilibrium becomes established. Often, it
is not greatly different from the original.
Gains and losses in ecosystems occur
Relationships in ecosystems
Remember
G
E
1 Identify one similarity and one difference between a predator–prey relationship and
parasitism.
2 Define ‘intraspecific competition’.
Benefitted
Species B
Commensalism
Benefitted
Predator–Prey
Parasitism
Predator:
Host:
Prey:
Parasite:
Competition
EC
Benefitted
TE
Species A
Symbiosis
D
Mutualism
PA
3 Complete the following table about interspecific relationships by indicating which
species is harmed, benefitted or unaffected:
O
R
R
Apply
4 In some eucalypt trees, leaves similar in appearance to the eucalypt leaves hang
down from the branches. These are leaves of the mistletoe plant. They can make
their own food but their stems send suckers into the eucalypt to obtain water
and minerals. If too much water and minerals are removed, the eucalypt can die.
Identify this type of relationship and the roles the eucalypt and mistletoe plants
play. Justify your decision.
U
N
C
5 Epiphytes are plants that grow up high in the branches of other trees, especially
rainforest trees. Examples are some orchids and ferns. The epiphytes obtain enough
light to make their own food, they collect water from the moist air, and they obtain
minerals from the decaying leaf litter they catch at their leaf bases. These plants do
not affect the tree. Identify this this type of relationship. Justify your decision.
Analyse and evaluate
6 Outline why it is important to have a variety of producers, consumers and
decomposers in an ecosystem.
7 Propose some ways that organisms could become extinct in an ecosystem.
8 Explain how predator–prey populations are interdependent. Are there any benefits
of this relationship for the prey?
9 Ecosystems are said to be in a state of equilibrium or balance. Give an example of
how a change in the environment may lead to changes in the living community and
overmatter
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3.1
Components of ecosystems
Remember and understand
8
If only 10% of the energy is
transferred along a food chain (Figure
3.29), explain what happens to the rest of
the energy. [2 marks]
1 Define abiotic and biotic components of
ecosystems. [1 mark]
5 Identify the products of photosynthesis
essential for cellular respiration. [1
mark]
Apply
11Some succulent plants that grow
in very hot and dry conditions have
reversed the opening and closing
rhythms of the stomata in the leaves
that allow gases to exchange. They
open during the night and close during
the day. Suggest a disadvantage for the
plants that do this. [1 mark]
PA
G
6 Describe how the flow of energy differs
from the flow of matter through an
ecosystem. [2 marks]
FS
4 Describe how plants obtain the raw
materials needed for photosynthesis.
[1 mark]
10Respiration in your cells provides
the energy for all your metabolic
processes. Identify six different cellular
processes that require energy from
respiration. [3 marks]
O
3 Outline the process of photosynthesis.
[2 marks]
9 Explain the difference between
respiration and photosynthesis.
[2 marks]
PR
O
2 Explain what mutualism, parasitism
and commensalism have in common.
How are they different? [3 marks]
E
Checkpoint
EC
TE
D
7 Can competition occur between
members of the same species and
members of different species? Explain
with examples. [2 marks]
R
1 unit of energy
Top
consumer
Heat
Heat
10 units of energy
Primary
consumers
N
C
O
R
Secondary
consumers
U
Decomposers
100 units of energy
Heat
Producers
1000 units of energy
Heat
Figure 3.29 Energy
transfer is diminished
along a food chain.
33 300 energy units
12Draw a concept map showing how
photosynthesis and respiration
are connected using the following
terms, plus any others you think are
appropriate: glucose, energy, oxygen,
carbon dioxide, ATP, water. [6 marks]
13Observe your school ground or your
home garden for about a week. Keep
a journal listing any examples of
interrelationships between organisms.
[2 marks]
Analyse and evaluate
14Is it more beneficial for a flowering
plant to be pollinated by only one
species of pollinator or a variety of
species? Explain. [2 marks]
15Analyse the marine Antarctic food web
in Figure 3.30.
Sun
a Identify the relationship between
humpback whales and lobsters.
[1 mark]
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b Identify the relationship between
emperor penguins and fur seals.
[1 mark]
c If overfishing rapidly decreases
deep-sea fish numbers, what
pressures could this place on the
seal population? [1 marks]
Deep-sea fish
d What pressures would overfishing
have on the humpback whale
population? [1 marks]
Squid
Phytoplankton
FS
Lobster
PR
O
O
Figure 3.30 A simplified marine Antarctic food web.
Rock platform
Acmea
PA
G
Lottia
E
16 Explain how the carbon–oxygen transfer
between animals and plants is like
a battery that powers the biosphere.
Think about how we use batteries and
how this can be similar to what happens
in photosynthesis. [2 marks]
D
Ocean
TE
17Our understanding of how plants work
has changed over time. Research
some of the important scientists in this
field and how they have contributed
to our understanding of plants. For
instance, who came up with the
name ‘photosynthesis’ and why? Who
discovered that plants release oxygen
during the day? You might like to
produce a timeline from Aristotle to the
21st century. [5 marks]
Orca whale
Fur
seal
Emperor
penguin
Humpback
whale
R
R
EC
18Limpets graze on algae on a rock
platform. The large limpet, Lottia,
is found in a territory containing
microalgae, and the smaller species,
Acmaea, is found on the edge of this
territory (Figure 3.31).
C
O
a Propose one possible reason
(hypothesis) for this situation. [1
mark]
U
N
b Describe an experiment you might
set up to test if your hypothesis is
correct. Identify the experimental
variable, the dependent variable
and the variables you would need to
control. [4 marks]
Critical and creative thinking
19Imagine it is your job to find out if soil
is ‘consumed’ as plants grow. Design
an investigation to test this idea. How
will you tell if the plant(s) have actually
Figure 3.31 Lottia and Acmaea on a rock platform.
consumed the soil? What evidence do
you need to collect? What variables do
you need to control? How will you set
up a control? What is the purpose of
the control? What is your hypothesis?
[5 marks]
Making connections
20Scientific understanding of the
relationship between plants and
animals in an ecosystem is an
important area of scientific research.
Ecologists are scientists who specialise
in this area of research. Examine what
an ecologist does. Write a paragraph
that describes the highlights of working
as an ecologist plus some of the
disadvantages. [4 marks]
TOTAL MARKS
[ /55]
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3.2
Changing populations
The population size of some species remains constant over time. Other populations change in
numbers. Population size is determined by natural factors such as births, deaths, immigration
and emigration, climatic change, natural disasters and introduced species. Human impact
may also have a major influence on populations of our own and other species.
E
PR
O
O
ecosystem may be to monitor the population
size of a particular species, or to measure the
biodiversity of the area.
Scientists can make predictions and
take certain precautions to conserve species
if they know approximately how many
of each species are in a certain location.
Regular sampling provides information
about increases and decreases in population
numbers, and causes of the changes can be
identified.
D
PA
G
A common indicator of the health of a
natural ecosystem is its biodiversity.
Biodiversity is a measure of the number
of different species in an ecosystem (bio
meaning life; diversity meaning different).
A rainforest with thousands of different
species has very high biodiversity, but
potentially a low population of each species.
A field of wheat might have millions of
individual plants in the population, but very
low biodiversity due to the vast majority of
individuals in the community being the
same species.
In any one ecosystem you must consider
all the different kingdoms represented.
Microorganisms are important to the
health and functioning of an ecosystem, as
are all the plants and animals. Significant
changes to any of the populations within the
community can seriously affect the others.
Ecosystems that have high biodiversity
tend to be more resilient to environmental
change. An individual species might die
out in that ecosystem, but due to the
different characteristics and adaptations
in the different species, some will survive
the change. For example, if a fungus infects
a field of wheat, it could potentially kill
every plant in the field. If one individual
is susceptible to that disease, it is likely
that every individual of the same species
will also be susceptible. However, if the
same fungal disease infected the rainforest
ecosystem, only some plants will be affected
while different species will have a natural
resistance and survive.
Population dynamics is the study of
the fluctuations (changes) in population
numbers within ecosystems. Surveys of an
FS
Population dynamics
Births
R
EC
TE
Immigration
U
N
C
O
R
Population size
Emigration when
food scarce
Deaths
Figure 3.32 A galah population in a particular area
depends on the food available and the number of
births and deaths.
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Activity 3.2.1: Human population
Consider the human population. The number of people in a population increases and
decreases in different parts of the world for a wide variety of reasons.
1 List as many reasons as you can for population change, then share your list with a
partner.
2 Contribute your reasons to a comprehensive class list. Identify the factors that:
• would cause increase or decrease in numbers
• are related to human actions.
3 Discuss whether or not these factors can or should be controlled.
E
G
PA
Figure 3.33 Quadrat
sampling counts every
organism within the
quadrat frame.
U
N
C
O
R
R
EC
TE
D
There are a number of ways to determine
the size of a population. Counting every
individual organism in a population is the
most accurate way, but in practice this is
rarely possible and very time-consuming.
Estimates are more easily achieved by
surveying from helicopters or using quadrats,
transects or capture–recapture methods. For
human populations, a census is the usual
method. A census actually takes information
about every individual in a population.
For plants and stationary animals,
quadrats (square plots) are most commonly
used for population estimates. The quadrat
frames are either randomly placed (tossed
over the shoulder) or sequentially marked out
in a designated area within the ecosystem.
Every individual is counted in each plot and
its species noted. An average number of
each species is calculated for each quadrat
and then used to estimate the total number
of organisms in the ecosystem (by using
the known total area of the ecosystem).
This method works well if a large number
of quadrats are used and the organisms
are small and relatively evenly spread or
dispersed throughout the ecosystem.
A line transect is an excellent method
of examining the diversity of an ecosystem
and the distribution of a particular species
over a varied ecosystem. A straight line,
often a measuring tape, is placed through
an ecosystem. Any organism that touches
the line (including directly under or over
it) is counted and its species noted. This
PR
O
O
Counting organisms
FS
• would cause significant or minor changes in numbers
Figure 3.34 Line transect sampling counts organisms that touch or cross the tape.
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An estimate of the population is then
obtained using the formula:
Estimated total number of animals
N ×N
E
PR
O
O
FS
1
2
   
​ ​​ 
= ​​ ​ ______
M2
It is assumed that the probability of
capturing animals on both occasions is
the same, but this is not always the case.
The animals may not like the traps and may
avoid them on the second occasion, or they
may love the bait (often muesli, honey,
peanut butter or oats for small mammals)
and deliberately come back for more! The
marking can be temporary, like food dye,
and wear off within a few days, or it can
be more permanent like leg rings, ear tags
or GPS inserts. These more permanent
tags enable ecologists to follow individual
animals over long periods of time and can
be used to gather data on distribution,
migration and long-term changes to
populations. But it is also important to
ensure the tagging does not affect the
normal lifestyle of the organism so it does
not affect its survival. For example, tagging
a possum pink would cause it to be more
visible to predators and less appealing to
potential mates.
Capture–recapture is a very suitable
technique for estimating the population
size of small Australian mammals such as
the marsupial Antechinus – the common
bush rat. Because most native Australian
mammals are nocturnal (awake at night),
the traps may be set at night and checked
the next morning.
U
N
C
O
R
R
EC
TE
D
PA
G
may be done along the whole length of a
short transect, or at regular intervals (every
metre) along a long transect. A number of
parallel transects can be used to calculate
an average of each species at each distance
along the line. Transects are also only used
for plants or stationary (sessile) animals.
They are particularly useful in an ecosystem
where the conditions change significantly in
predictable bands, like intertidal zones.
For most mobile animals, capture–
recapture is a popular method for
population estimation. Animals are captured
in traps then marked with tags or other
marks such as food dye or permanent
marker on their tails, feet or other easily
seen body parts. The number counted on
the first capture is N1. The animals are then
released and it is assumed they disperse
evenly throughout the population. They are
then recaptured one or two days (or nights)
later and the total number of animals in the
second capture is N2. Not every animal that
was captured in the first trapping session
will necessarily be caught the second time,
and new individuals may be captured in
the second trapping session. The number of
marked animals in the recapture, those that
have been captured twice, is M2.
Figure 3.35 Once captured, many measurements are
taken and recorded for each individual before they are
marked and released.
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caught (N2), of which 12 were tagged (M2),
the estimate of the population would be
275 fish.
Capture–recapture
population estimates
Capture–recapture is a common technique
for estimating animal populations. To
obtain accurate estimates, the process
may be repeated over a number of weeks
and the estimates averaged.
Estimated total number of animals
N ×N
1
2
   
​ 
=​ _____
M
2
55×60
   
​ 
=​ _____
12
Estimated total number of animals
FS
3300
  
​ 
=​ ____
12
N1×N2
   
 
​
=​ _____
M2
=275
where:
N1 = the total number of individuals
captured and marked in the first
session
O
Your turn
A team of ecologists was hired to
investigate the population of ring-tailed
possums in Katoomba, NSW. On the first
night they captured 48 possums, marked
their tails with blue food dye and released
them. Two nights later they trapped 42
possums, only 8 of which had blue dye on
their tails. Estimate the population of ringtailed possums.
PR
O
N2 = the total number of individuals
captured in the second session.
If 55 fish were initially captured and tagged
(N1) and then one day later 60 fish were
D
PA
Example
G
E
M2 = the number of individuals already
marked in the second capture.
Student Design Task
N u m e r ac y
bu i l d e r
EC
TE
Estimating populations
Work in small groups of about three students. Tasks should be allocated to each
member of the group.
Challenge
R
Estimate the size of a plant population in a local ecosystem.
R
Questioning and predicting
N
C
O
• Choose a suitable ecosystem in which to work.
• Discuss any potential difficulties, for example, how to find (or estimate) the total
area of the ecosystem.
• Choose a suitable organism to survey – it could be an animal or a plant species.
• Predict the approximate size of the population, if this is feasible.
U
Planning and conducting
• Determine the equipment required and write a proposed method for the activity.
Check this with your teacher.
• Conduct the investigation, recording all results neatly and clearly.
Processing, analysing and evaluating
1 Perform all necessary calculations and record them in an appropriate format.
2 Evaluate how your result agrees with the prediction you made before you conducted
the investigation.
Problem solving
3 Analyse your method. Is there anything you would change if performing this
investigation again?
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Communicating
Write a full report of your investigation. Include the following: your initial questions,
predictions and plans for the experiment; the method used to conduct the experiment;
how the results were recorded and processed; the analysis and evaluation; and any
references used. Each section should be clearly identified.
Questions 3.2.1: Population dynamics
Remember
FS
1 Suggest a reason why populations are estimated rather than just counted.
2 Recall the name of a population survey that counts every individual.
O
3 Identify the most suitable method for estimating the size of populations of:
PR
O
a spinifex grass
b periwinkles
c blue-tongue lizards
U
N
C
O
R
R
EC
TE
D
PA
G
E
4 Justify your reasons for selecting the sampling techniques for each part question 3.
Figure 3.36 How would you estimate the
population of (a) spinifex (b) periwinkles (c)
blue tongue lizards?
Apply
5 Students on a field trip with a national park ranger set traps for a small nocturnal
marsupial, Antechinus stuartii, in a heathland ecosystem. They capture 8 animals
on the first night and mark them with white dots on their tails. Then they release
them. On the second night they capture 10 animals, of which 4 are marked.
a Calculate the estimation of the population size of Antechinus stuartii in this
ecosystem.
b Explain how the students could increase the accuracy of this investigation.
Analyse and evaluate
6 Is a growth in population size always desirable? Discuss.
7 Suggest some factors that may affect the population growth of A. stuartii.
8 Outline the advantages and disadvantages of quadrat sampling.
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Natural factors affecting
populations
EC
R
R
O
C
N
U
Figure 3.37 Rabbit populations grow rapidly when
conditions are right.
FS
Figure 3.38 Short-tailed
shearwaters leave their
burrows on Montague
Island on the southern
coast of New South
Wales and fly to feeding
grounds in the area of
the Bering Sea during the
northern summer. They
return for breeding in late
September.
O
G
E
PR
O
When the weather becomes colder, many
birds and other animals migrate to areas
with warmer temperatures, resulting in their
population significantly decreasing in one
environment and increasing in another.
During the breeding season, usually spring,
numbers of animals will increase as the
next generation is born. Flowering plants
are pollinated and form seeds that disperse
(spread out) in the environment and later
germinate.
Presence or absence
of organisms of other
species
TE
All populations are limited in size by their
carrying capacity. This is the maximum
number of species members that the
environment is able to support in terms of
resources. As a population increases and gets
close to its carrying capacity, some of the
environmental resources will be significantly
depleted. Competition for the resources
will increase, because there simply isn’t
enough food, water or shelter to go around
if for so many individuals. Some organisms
will either die or leave the area. Hence, the
Seasonal changes
PA
Limiting resources
population will stabilise (reach its maximum
size). Only one resource needs to be limiting
to restrict the size of a population. That
resource may be nesting sites, a food or water
source, physical space or light availability for
plants, or many other examples.
D
What causes the changes to the births,
deaths, emigration or immigration
that may change a population size? The
dynamic equilibrium of a population
means there are continual small changes
to the population size, but overall the total
number of individuals remains roughly the
same. New births and immigration into
the area cause the population to increase,
while deaths and emigration cause it to
decrease. Significant or relatively long-term
changes to population size are usually due
to specific events. Many of these changes
are natural, but others are caused by
human intervention. Natural impacts on
populations may include any of several
different factors.
Predators and competitors may decrease
population numbers. Some organisms
will be familiar with these species and
have ways to avoid predation or increase
their own ability to compete for resources.
Introduced predators and competitors can
have devastating effects on resident species.
Organisms will need to adapt quickly to
avoid predation (being preyed upon) and
will have to ‘fight’ for resources.
Disease
The introduction of a disease into a
population may have a major or minor
impact on a species. The impact will be
determined by the cause of the disease and
the species’ ability to fight it. Like humans,
prior exposure to a disease can enable
organisms to launch a successful immune
Figure 3.39 Small birds
are vulnerable to the
predatory activities of
larger birds. The pied
currawong preys on the
nests of smaller birds
along the eastern coast
of Australia. Currawongs
have a varied diet that
includes berries, insects
and small vertebrates
(including small birds).
Figure 3.40 The
Tasmanian devil has
become a victim of
facial tumour disease,
a very unusual type of
cancer because it can
be transferred from one
animal to another. There
has been an average 40%
decrease in devil sightings
across Tasmania, and
a 90% decrease in the
overmatter
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FS
O
However, evidence of warming in the
Arctic is mounting year on year – with
serious consequences for biodiversity. One
well-publicised impact of warming is the
loss of habitat for species dependent on
sea ice, such as polar bears.
But this is only one change. Across the
Arctic, many habitats that are considered
critical for biodiversity, such as the tundra,
have been disappearing over the last few
decades.
Launched to coincide with the 10th
Meeting of the Parties to the Convention on
Biological Diversity in Nagoya, Japan, the
report, entitled Protecting Arctic Biodiversity:
Strengths and limitations of environmental
agreements, was researched by UNEP’s
Polar Centre GRID-Arendal in Norway. The
report underlines that although tried and
tested solutions to the current biodiversity
crisis in the Arctic exist in the region itself,
important conservation gains will only be
won if root causes originating outside the
Arctic region are addressed.
Achim Steiner, UN Under-Secretary
General and UNEP Executive Director,
said: ‘We are currently witnessing
unprecedented change in the Arctic, which
will have important and far-reaching
PA
Global action needed
to conserve Arctic
biodiversity
PR
O
Extreme natural changes have varying
population effects. For example, bushfires
can produce ash containing minerals
suitable for seed germination, and many
E
Literacy
builder
Extreme natural changes
native Australian plant species need fire to
release their seeds from the woody fruits.
In both these cases, bushfire results in a
population increase. If the fires occur too
frequently, young plants can be destroyed
before they can produce their own seeds.
Animal populations can be severely reduced
because they may be killed in bushfires or
they may flee to other ecosystems.
Drought affects all organisms, as water
is a vital resource for life. Plant and animal
populations will suffer as the availability
of water reduces and competition for it
significantly increases. Floods, earthquakes
and all other natural disasters affect
population sizes, usually reducing them
significantly as individuals are killed
outright, or the resulting loss of resources
increases competition.
G
Figure 3.41 Banksia
plants need fires with a
frequency of about seven
years to enable seeds to
be released, germinate
and produce small trees
or bushes that can
produce their own seeds.
response. Completely new diseases are likely
to have more of an effect on a population.
Populations with little genetic variation
(populations that are small or heavily
interbred) tend to have similar resistance
to disease. One new disease may have the
ability to wipe out the entire population.
The cheetahs in Africa are very vulnerable
due to their small numbers and low genetic
variation. This effect is also seen more
locally with the Tasmanian devil and their
low resistance to facial tumours.
United Nations Environment Programme
D
Nagoya, Japan, 27 October 2010
U
N
C
O
R
R
Figure 3.42 Polar bears
depend on sea ice for
survival.
EC
TE
The Arctic is experiencing some of the
most rapid environmental changes on the
planet. Whilst this presents enormous
challenges for conserving biodiversity, it
also offers opportunities for enhancing
cooperation between nations and
reforming environmental governance
to meet the challenges of the
21st century, according
to a report by the UN
Environment Programme
(UNEP).
The Arctic
contribution to
global biodiversity is
significant. Hundreds
of migrating species
(including 279 species
of bird and the grey and
humpback whales) travel
long distances each year
in order to take advantage of
productive Arctic summers.
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contaminants and habitat fragmentation,
are essentially global in nature. Tackling
these threats will require identifying
international agreements that are relevant
to biodiversity, but in new, unconventional
ways.
Questions
FS
1 Discuss why changes in the Arctic
region will have ‘far-reaching
consequences … for the rest of the
world’.
PR
O
O
2 List the factors described in the article
that affect population sizes in the
Arctic.
3 Why is an international approach to the
problem of biodiversity in the Arctic
essential?
E
consequences not only for the region itself,
but for the rest of the world.’
The rapid changes in the Arctic are
perhaps the most striking example of
how interconnected our world is, and
how policies in one part of the world
can severely affect the environment,
biodiversity and livelihoods in another.
The report finds that existing
multilateral environmental agreements
that include the Arctic region … might be
effective against threats caused by local,
national, or regional activities (mining and
oil and gas exploitation, for example) if
adequately implemented.
This is because the fundamental
threats to Arctic biodiversity, such
as climate change, transboundary
G
Questions 3.2.2: Natural factors affecting populations
6 Explain why a population with low
genetic diversity is more susceptible
to disease than one with high
diversity.
EC
TE
2 Identify a limiting resource for plants,
other than water. Explain why this
resource would limit the size of
populations.
PA
1 In relation to resources, explain what
‘limiting’ means. How does this differ
from ‘limited’?
numbers of Tasmanian devils.
You may want to consider some
interactions the Tasmanian devils
have with predators and prey, as well
as the environment.
D
Remember
R
3 Identify at least two animals you know
of (other than birds) that migrate due
to seasons.
O
R
4 Using a specific example, recall how a
bushfire might increase the size of a
population.
8 Disease is a big threat to human
populations. Can you identify any
recent diseases that have had serious
consequences?
U
N
C
Apply
5 Construct a flow diagram showing
some of the consequences of reduced
7 Explain how seasonal changes and
migration could be linked to changes
in limiting resources.
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Human factors affecting populations
likely to result in significant changes to
populations within ecosystems. Animals that
previously lived in the habitat will migrate or
die. Plant removal may reduce pollination of
similar species in the area as well as reduce
nesting sites for many animals.
Pollution
O
O
R
R
EC
TE
D
PA
G
E
At present, the human population is about
seven billion and is predicted to rise to
about nine billion by 2050. Humans have
developed technologies that efficiently
remove resources from the environment.
Human activity has introduced many
chemicals into ecosystems. Some chemicals
can cause mutation and/or death of certain
species and, in some cases, can result in the
collapse of entire food webs. A common
pollutant into waterways is fertiliser runoff.
The excess nutrients in the water cause
blue–green algal blooms – eutrophication.
Although these microorganisms
photosynthesise, once the bloom is
over they die and decay, which removes
dissolved oxygen from the water, starving
all other aquatic organisms of oxygen.
The microorganisms also grow across the
surface of the water blocking sunlight from
reaching photosynthetic organisms lower
down in the water, preventing them from
replenishing the oxygen in the water.
Irrigation increases fertiliser runoff. On
the east coast of Queensland, this runoff
PR
O
Competition for
resources
FS
While there are plenty of natural impacts
on populations, the effect of human
intervention is felt in many ecosystems
to varying degrees. Humans can have a
significant short-term or long-term impact
on ecosystems and the wellbeing and
survival of other species.
Demand for food is increasing with the
human population, which means more
pressure on the natural resources of the
land and sea. These resources may be needed
by other species. For example, humans use a
lot of water from the Murray–Darling Basin
for agriculture, which seriously affects other
species that depend on the river system.
The river red gum forests that surround
the Murray River have been placed under
extreme stress during droughts.
Permanent removal of habitats by
humans to use the land for building or
agriculture, or the trees for wood, is very
U
N
C
Figure 3.43 Numbers
of Murray cod, and
other native fish,
have decreased
significantly due to
irrigation, overfishing
and competition with
introduced species. Some
have been declared rare
or endangered.
Figure 3.44 Some substances in detergents and
fertilisers on agricultural land have washed into
oceans, lakes, river and other water bodies. This can
lead to eutrophication – an increase in organisms
that reduce oxygen levels in the water, harming other
organisms.
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FS
also carries topsoil and silt into the ocean.
Once in the ocean, the silt settles on top of
the coral reef as ‘marine snow’, suffocating
the coral polyps and blocking out the sun
for their photosynthetic symbiotic algae.
Coral growth is extremely slow, so the death
of sections of the reef is devastating to the
reef ecosystem.
Many industries now have much more
restrictive rules about the chemicals they
can release into the environment.
Figure 3.45 Botany
Bay, near Sydney, was a
natural ecosystem when
James Cook first sailed
into it in 1770. Today, it
is an urban ecosystem
because of many humaninduced changes.
PR
O
E
G
PA
D
R
R
EC
TE
Increasing numbers of humans, increasing
wealth and more sophisticated technology
have resulted in large amounts of fossil
fuels being used for transport, industry,
agriculture and electricity. Burning of these
fuels is contributing to the amount of
carbon dioxide in the atmosphere and to the
enhanced greenhouse effect.
More carbon dioxide means more
trapped heat, causing an overall average
increase in the global temperature. But
while some areas are getting hotter, others
are getting colder. In some ecosystems,
regular seasonal changes are becoming less
predictable, and extreme weather events
are occurring more often. Organisms that
cannot adapt to these changes in their
ecosystems will either emigrate or die.
and camels are hardy animals well adapted to
our arid climates, flourishing in the bush and
outcompeting native grazers.
However, not all effects of introduced
species are negative. The increased
pastureland for cattle and sheep has also
increased grass for kangaroos and wallabies
to eat, enabling native populations to
increase in some ecosystems. Human homes
and tips provide ample food and shelter for
many bird species.
The introduction of the cactus moth,
Cactoblastis cactorum, was a successful
application of biological control for
the prickly pear cactus. Huge areas of
pastureland were overgrown with the
introduced cactus and nothing seemed
to eat it. The prickly pear continued to
reproduce and spread without a natural
grazer until its natural predator, the cactus
moth, was introduced. This moth lays
its eggs on the cactus and the grubs that
hatch eat it. The grubs don’t eat any native
Australian plants and therefore do not
harm any other plants. When the number
of cactus plants reduced, the moths had
nowhere to reproduce and so died off,
causing no lasting negative impact on the
ecosystem.
Biological control is the carefully
considered and planned introduction of
species to an area to control the populations
of a pest species. The pest species may be a
native species with uncontrolled population
growth, or it may be an introduced species
like the prickly pear or cane toad. The
introduced species does not need to be a nonnative – they may be native to the country,
O
Enhanced greenhouse
effect
O
Introduced species
U
N
C
Humans have introduced many plant and
animal species to Australia as a whole, but
also to specific ecosystems. Foxes, rabbits,
cat and dogs, cattle and other livestock,
crop plants and decorative plants were all
introduced for food, sport, familiarity or
companionship. All of these new species
compete with native species. New predators
have devastated native populations that have
not adapted to avoid them.
The introduced cane toad is still spreading
south, outcompeting many other toad and
frog species, and poisoning potential native
predators like quolls and owls. Feral goats
overmatter
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O
PR
O
Figure 3.46 Davies waxflower is a critically
endangered Australian plant.
To protect the species, some of the areas
where it is found have been fenced. One
of the properties with the species even
has a conservation covenant in place – an
agreement between the landowner and
the state government that permanently
protects the nature conservation values of
the property.
Source: Australian Government, Department
of Sustainability, Environment, Water,
Population and Communities
EC
TE
D
PA
G
More than 60 Australian plant species are
now thought to be extinct, and over 1180
are threatened. One of these is Davies’
waxflower.
Davies’ waxflower (Phebalium daviesii)
is a shrub or small tree that grows
to about five metres. It is endemic to
Tasmania – that is, it is found nowhere
else in the world. It is known from only
three sites along the George River near
St Helens, on Tasmania’s east coast. The
species was thought to be extinct until it
was rediscovered in 1990. It grows in the
flood zone close to the river in eucalypt
woodland.
Most specimens of Davies’ waxflower
are on private land, next to pasture, and
cleared land where cattle feed. Cattle
cause problems of trampling, high nutrient
levels and compacted soil. The species is
also susceptible to root rot fungi, and any
activities that involve movement of soil will
increase the risk of infection.
As part of the conservation strategy,
and to promote community awareness,
the Davies’ waxflower has been planted
in St Helens and even in private gardens.
FS
Threatened Australian
plants
E
Deeper
u n d e r s ta n d i n g
Questions 3.2.3: Human factors affecting populations
R
Remember
R
1 Define the term ‘biological control’.
U
N
C
O
2 Describe an example of humans competing for resources with a native species.
Apply
3 The greenhouse effect is the natural trapping of heat against the surface of the
Earth by the atmosphere. Suggest what the enhanced greenhouse effect might be.
4 Currawongs are said to be opportunistic feeders, and tend to have large
populations near where humans live. Currawongs also tend to compete with
small birds for nesting sites and resources. Could it be said that the impact
of currawongs on the populations of small birds is a human impact? Discuss
your answer.
5 The fox is an introduced species in Australia. Outline what impact this animal has
on native species.
6 Of the resources used by humans, which would you classify as ‘needs’ and which
would you classify as ‘wants’? Explain your reasoning.
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7
Changing populations
Ethical understanding
1 Identify some examples of how
humans, especially since European
settlement, have changed Australian
ecosystems because of introduced
species. [2 marks]
8 Do you consider your personal use of
resources to be excessive? Do you try to
reduce your use of resources? Do you
think you should? Discuss. [3 marks]
5 Recall the term used to describe
oxygen depletion in aquatic ecosystems
due to algal blooms in response to
excess nutrients. [1 mark]
O
PR
O
E
TE
Apply
10On a global scale, the main energy
sources are oil (~35%), coal (~23%),
natural gas (~21%), biomass and waste
(~10%), nuclear (~6%) and hydro (~2%).
Wind, solar and geothermal power
together account for only 2%. Of all
the sources, over 80% are based on
fossil fuels. What do you think should
be the focus of energy providers for the
future? Should the people of Australia
be involved in these decisions? Explain
your answers. [5 marks]
G
4 Suggest the characteristics of the
organisms for which you would use
quadrat sampling to estimate the
population. [2 marks]
Critical and creative thinking
PA
3 Use a specific example to describe how
seasonal changes cause changes in the
size of populations in an ecosystem. [2
marks]
9 Many would argue, with respect to
resource use, that one person cannot
make a difference. Do you agree?
Discuss. [3 marks]
Checkpoint
D
2 Describe some other significant ways
in which humans have affected natural
populations in ecosystems. [2 marks]
3.2
FS
Remember and understand
Making connections
11Select an environmental impact to
investigate that is either natural or
caused by humans. Imagine you are
an environmental scientist. Design an
experiment to test the level of impact
and the timeframe in which it would
occur. You do not need to be able to
conduct this experiment. [5 marks]
N
C
O
R
R
EC
6 The glaciers on Mt Kilimanjaro are
melting, as are many other glaciers.
Less water in the nearby lake system
affects the water cycle, causing less
cloud coverage. This allows more
sunlight to reach the glaciers. The
increase in sunlight provides more
energy for melting of the glaciers.
Explain how cloud cover can affect the
atmospheric temperature and hence
the melting of glaciers. [3 marks]
U
Analyse and evaluate
7 The human population was fairly stable
until about 1 ad. In the past century it
has almost quadrupled. Evaluate the
likely effects of population increase on
world ecosystems. [2 marks]
TOTAL MARKS
[ /30]
Changing populations 115
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Evidence suggests that humans have lived in Australia for 60 000 years. Fossils and rock art
have shown that natural and human-induced changes have occurred to natural ecosystems
over that period. In contrast with the early European settlers, the Australian Aboriginals
and Torres Strait Islanders understood the constraints of the environment, yet their
understanding was not respected. Today, our way of life makes many competing demands
on the natural environment. Indigenous knowledge as well as scientific understanding and
technology are being used to try to appropriately manage sustainable ecosystems.
O
FS
3.3
Managing sustainable
ecosystems
PR
O
Aboriginal land management
U
N
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TE
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PA
G
It is believed the name ‘Kakadu’ is derived
from the local Aboriginal language
Gagadju. The Gagadju-speaking Aborigines
were believed to be that region’s original
inhabitants about 50 000 years ago.
Kakadu wetlands faced a problem after
the removal of all feral Asian water buffalo
in the 1980s. The buffalo kept the native
grass mudja (Hymenachne acutigluma) in
check, but after their removal it spread,
choking out wetland plants, restricting the
feeding of water birds, reducing the variety
of habitats and limiting access for hunting
and food gathering by Aboriginal people.
The solution involved a return to traditional
fire management practices. Mudja had
not been a problem before the buffalo
introduction because regular burning by
Aboriginals had maintained biodiversity and
supported their ability to hunt and gather
food throughout the year.
E
Kakadu: burning for
biodiversity
Figure 3.47 The wetlands of Kakadu National Park in the Northern Territory are an ecosystem with very high
biodiversity.
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O
season in December, the
mudja is burnt.
The result has
been an outstanding
success. Populations
of turtles, magpie
geese, other wetland
birds and water lilies
have increased. Plant
variety such as wild rice
and spike rushes and a
greater variety of habitats,
including more open water,
now can be seen. Care is being
taken to ensure the traditional
knowledge is recognised,
remembered and passed to the
next generation.
Figure 3.48 Carefully
controlled burning
of some ecosystems
can prevent the over
dominance of particular
plant species to maintain
high biodiversity and
reduce the impact of
natural bushfires.
PA
fills with water during high-rainfall years,
due to excessive flow of fresh water
from rivers in outback Queensland, it
is virtually a freshwater lake. Native
freshwater fish such as bream and
golden perch can live in it until it
becomes too salty due to evaporation.
• Identify the abiotic factors in
components of the ecosystem at Lake
Eyre that affect populations.
• Explain the word ‘sustainable’.
• Could the lake ecosystem be
described as a sustainable
ecosystem? Discuss.
b
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a
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Lake Eyre is a massive lake that lies in
a remote area of inland Australia. Most
of the time, the lake is completely dry.
Without water, a salt crust of nearly half
a metre covers a quarter of the surface.
Several major rivers empty into Lake Eyre
but carry water only about once every ten
years. When water does reach Lake Eyre,
as occurred in late 2010, early 2011 and
early 2012, large numbers of birds return
to breed.
The explosion in the populations of
ibis, pelicans and other bird species
in Lake Eyre in 2010–2012 has been
striking. During droughts, Lake Eyre is a
salt flat with few animals visible. When it
G
Activity 3.3.1: The extremes of Lake Eyre
E
PR
O
Traditional ecological knowledge has
been combined with modern science to
develop and monitor the solution. CSIRO
and the Bushfire Cooperative Research
Centre worked with a family of traditional
owners in Kakadu as part of a northern
Australian ‘Burning for Biodiversity’
project. The project applies Aboriginal fire
management in the Boggy Plain floodplains
of the South Alligator River and now also
the well-known Yellow Water wetlands.
Woodlands and paperbark forests
that surround the grasslands are burnt
progressively between May and August, early
in the dry season. This ensures there is little
fuel beyond the grasslands so later grass
fires remain contained. From September to
the beginning of the downpours of the wet
Figure 3.49 Lake Eyre in (a) drought and (b) flood.
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FS
PA
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A series of rock wall constructions in the
river at Brewarrina are part of Australia’s
National Heritage and evidence of how
the local Ngemba people understood their
local environment including the water
flows, fish migrations and movements.
O
Reliability of secondary source information
is important. One way of ensuring
reliability is to use a number of different
information sources and check for
consistency. It is also important to check
the source of the information because not
all Internet sources are accurate.
Read the following information about
fish traps and conduct your own research
to validate it. Write a bibliography of the
sources you use. You could present your
findings as a table of facts identifying them
as accurate, partially correct or incorrect,
listing the sources you used to validate
each one.
Brewarrina Aboriginal fish traps
They built stone walls, called Ngunnhu,
in the shallows of the Barwon River in a
complex arrangement. Some claim the
walls that served to trap fish are 40 000
years old and, as such, would be the
oldest remaining human-built structure.
This area was, and remains, a significant
Aboriginal meeting place. The use of
the fish traps was managed to ensure
responsibility for each trap and that
overfishing did not occur. Other local tribes
also benefited from the fish traps.
Indigenous fish traps are also found in
estuaries and along the coast. One of the
most extensive systems is the collection of
eel traps in the Mount William swamp and
Lake Bolac of Victoria. The local Aboriginal
tribes built an extensive network of
channels, weirs and eel traps. Combined
with their knowledge of eel migration, this
allowed a ready supply of food sufficient
to allow bartering, and semi-permanent
settlement.
PR
O
Research
E
Sc i e n c e
skills
TE
D
Uluru and Kata Tjuta:
Reducing human impact
U
N
C
O
R
R
EC
Have you ever visited Uluru or Kata Tjuta
(the Olgas)? This area contains one of the
most significant arid land ecosystems in the
world. It receives less than 250 millimetres
of rainfall per year. Despite the harsh
Figure 3.50 Puli habitat.
climate, this area is home to hundreds of
different organisms.
When early European explorers first
visited this region in the 1870s they were
confronted by a harsh landscape. Their
initial aim was to find a route for the
overland telegraph line from Adelaide to the
Top End, and to set up pastures for sheep
and cattle grazing. They soon decided the
region was unsuitable, and left.
However, the traditional owners of the
land, a group of Anangu Aboriginal people,
had lived on this land for thousands of
years and understood it well. They lived
a nomadic life, travelling in small family
groups and surviving by hunting wildlife
and gathering food from the land. In this
way they did not over-harvest the land and
gave it plenty of time to recover between
visits, ensuring there would always be
enough resources for when they returned.
These sustainable hunting and gathering
practices meant people could successfully
live in a very fragile and harsh ecosystem.
The Anangu knew where to find food
to survive and, more importantly, which
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O
PR
O
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G
E
Figure 3.51 Puti habitat.
U
N
C
O
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R
EC
TE
D
areas were best for hunting and gathering
at different times of the year. The Anangu
classified their environment to help them
locate the precious food. They used these
names:
Puli: rocky areas, gorges, stony slopes.
Animals come to this area to find shelter
and water. Euros, fat-tailed antechinus,
echidna and black-footed rock wallaby can
be found here.
Puti: open woodland. After the rains, this
area has an abundance of grass, which the
kangaroos eat. Honey ants build their nests
in this area. Trees include mulga (a wattle),
desert oak, desert poplar, desert bloodwood,
river red gum and blue mallee. Wattle seed
is an important food. Witchetty grubs live
on the roots of the witchetty bush. Red
kangaroo, euros and the spinifex hopping
mouse are found here.
Pila: spinifex plains, low areas between
dunes. This is the best place to gather seeds
to eat. There are over 50 species of desert
grass. Many types produce seeds that are
gathered and ground to make flat breads
and damper. Resin is gathered from gummy
or soft spinifex, and used for making and
repairing hunting and working implements.
Other habitats include the creek lines
(karu) and sand dunes (tali). These become
nyaru after fires.
The Anangu also distinguished five
seasons:
Piriyakutu or piriya piriya (usually
August–September) – A warm steady
wind from the north and west (piriya)
predominates. Animals, and plants
such as the honey grevillea, reproduce.
Reptiles become more active. Food is available
and it is a good time for hunting kangaroos.
Mai wiyaringkupai or kuli (around
December) – This is the hottest season,
when food is scarce. Storm clouds (ngankali
or marutjara) build up, producing lightning
but little rain. Bushfires started by lightning
strikes occur.
Itjanu or inuntji (January–March) –
Overcast clouds (utawari) bring sporadic
storms and food plants flower.
Wanitjunkupayi (usually April–May)
– The weather starts to turn cold and the
Figure 3.52 Pila habitat.
reptiles become less active. Tjuntalpa clouds
start to occur around April but sit low over
the hills until evening. They do not usually
bring rain.
Wari (June–July) – The cold season
bringing morning frosts (nyinnga), and mist
or dew (kulyar-kulyarpa) most mornings but
little rain. The frosts dry and preserve the
grasses as fuel for the fires ignited in the hot
season.
Introduced species have affected the
Uluru–Kata Tjuta communities. Buffel grass
was used to reduce erosion in some areas,
but has spread and is now having a major
effect on the diversity and distribution of
overmatter
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Questions 3.3.1: Aboriginal land management
Remember
1 Explain how traditional burning techniques were used in Kakadu. What benefit did
it bring to the environment?
2 The early European explorers abandoned the arid ecosystem around Uluru and
Kata Tjuta because they couldn’t survive. Explain why they struggled to find food
there.
Apply
4 Discuss Aboriginal land management in terms of:
O
a a nomadic existence
FS
3 Recall the reason why mudja grass needed to be managed with fire.
b use of fire
PR
O
5 In a group of four, create a list of the biotic factors and another list of the abiotic
factors important to the ecosystems in Uluru–Kata Tjuta National Park. One pair
can create the ‘biotic’ list and the other pair creates the ‘abiotic’ list.
E
6 Suggest a reason why the Anangu people devised a system of classification for the
natural habitats around them and the seasons they experienced.
PA
G
Research
7 Follow the obook link to find out about the kind of environment the Anangu live in
and foods they traditionally ate to survive. List at least five animals and five plants
food sources.
D
8 Research one example of how Aboriginal people have used their knowledge to
conserve and manage their environment.
U
N
C
O
R
R
EC
TE
9 Research the general differences between Aboriginal land management systems
and those of Europeans.
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People in Australia expect a lifestyle that provides essential food, clothing and shelter, but
also many additional comforts. Meeting these demands can damage natural ecosystems.
Environmental sustainability is about balancing the way we live with its impact on
ecosystems. For sustainable practices to begin and to continue, individuals, communities
and governments need to work together.
Table 3.5 includes the benefits and problems of some local strategies used to balance
human activities and needs with conserving, protecting and maintaining the quality and
sustainability of the environment.
Table 3.5 Some local environment strategies.
FS
Sustainability and ecosystems
Benefits
Problems
Recycling
Materials such as aluminium can be
recycled indefinitely with a fraction of
the energy required to extract it from
the ore.
Some materials, such as paper, cannot be
recycled indefinitely because of loss of quality.
Recycling requires money, time and effort for
collection, sorting and processing.
‘Organic’
agriculture
Less fertiliser run-off and fewer
beneficial insects killed by pesticides.
Pesticides do not enter the food web
and become more concentrated at the
top consumers.
Less productive and profitable for farmers.
Higher prices for customers.
Promoting
alternatives to
car transport
Reduces the pollution from cars.
Reduces use of fossil fuels.
May require more infrastructure such as
cycleways and train lines.
Changing behaviour is not easy when
alternatives to cars may be less convenient.
Public cleanup activities
such as
Clean-up
Australia Day
Removes plastics and nonbiodegradable rubbish from
ecosystems.
Raises awareness.
Requires energy and effort to coordinate and
collect waste.
Not as effective as producing less waste to begin
with.
Bush
regeneration
Allows native flora and fauna to reestablish in disturbed ecosystems.
TE
D
PA
G
E
PR
O
O
Strategy
EC
Requires energy and effort to coordinate.
R
Activity 3.3.2: Science and sustainability
U
N
C
O
R
Choose one activity in your local area that aims to help maintain or create a
sustainable environment. Assess the benefits and problems associated with the
activity. Identify whether science or technology is playing a part in the activity. If so,
explain how. Identify whether you as an individual can participate in the activity in
some way.
Present your findings in a format of your choice, but use one digital technology in
your presentation.
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U
N
C
O
R
R
EC
TE
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FS
PA
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Around 100 Indigenous Working on
Country rangers from across southern
Australia have come together for the first
time this week to share knowledge and
experience in protecting our environment
and conserving biodiversity.
Rangers have had the opportunity to
showcase their work, strengthen their
skills in land and sea management,
celebrate their achievements and help
build sustainable communities.
There are now almost 700 rangers
supported under Working on Country
around Australia and over 20 Working on
Country ranger teams operating across
southern Australia.
This was the first regional gathering for
Working on Country rangers and for most
of them it will be the first time they have
met.
The conference, from 16 to 20 April
2012 at Calperum Station near Renmark
in South Australia, is funded by Working
on Country as part of the Caring for
our Country initiative. The Australian
Landscape Trust, which manages
O
20 April 2012
Calperum and Taylorville Stations
and supports the Working on Country
Riverland Indigenous ranger team, is
hosting the event.
Workshops include Aboriginal site
recording, media skills, fire management,
quad bike safety, water quality monitoring
and using new technology in landscape
management.
The Working on Country Indigenous
ranger program is achieving
environmental outcomes in the national
interest and supporting the Australian
Government’s commitment to Closing the
Gap.
Working on Country recognises
Indigenous people’s strong relationship
and obligations to country and their desire
to have their land and sea management
work recognised as paid employment.
Vast areas of Australia are cared
for by Indigenous people who deliver
environmental services of benefit to
the nation, including the management
of cultural sites, heritage values, fire
regimes, biodiversity, feral animals,
weeds, land disturbance, pollution and
climate change impacts.
In this way, Working on Country brings
together Indigenous caring for country,
environmental and employment outcomes.
PR
O
Working on Country
Southern Ranger
Conference
E
Literacy
builder
Source: Department of Sustainability,
Environment, Water, Population and
Communities
Questions
1 How do you think sustainable
communities of Indigenous ranger
teams contribute to sustainable
ecosystems in Australia?
2 Why are collaboration and
communication important to ecosystem
management?
3 What special skills would Indigenous
rangers bring by caring for cultural and
heritage values?
Figure 3.53 Working on Country integrates
Indigenous knowledge and practice with nationally
accredited qualifications to deliver positive
environmental outcomes.
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Rio+20: UN Conference on Sustainable Development
PR
O
O
FS
The United Nations Conference on Sustainable Development, known as Rio+20, was held
in Rio de Janeiro, Brazil, in June 2012. It followed on from the Earth Summit held 20 years
earlier in Rio. Governments and organisations from many countries met to discuss ways to
reduce poverty while at the same time using resources in a fair and sustainable way. Some of
the priorities for the conference were energy, water and sustainable cities and agriculture.
The conference participants recognised that ending poverty, changing the amount
we produce and consume, and protecting the natural environment are all essential for
sustainability. Developing countries need support to find a ‘green’ path for development,
and cooperation and organisation between countries are very important for sustainable
development.
There is concern among environmental groups that the outcomes of the conference will
not be committed to and may not happen soon enough.
Questions 3.3.2: Sustainability and ecosystems
Remember
1 Define ‘environmental sustainability’.
PA
4 Identify the purpose of the Rio+20 conference.
G
3 Recall an advantage of bush regeneration.
E
2 Recall why paper cannot be indefinitely recycled.
D
Apply
5 Describe two ways in which human activities conflict with sustainability and
ecosystems. Which is more important?
TE
6 Outline some examples of ways that you personally can help maintain a sustainable
environment.
7 Are sustainability and modern life compatible? Discuss.
EC
8 Describe how local and global activities both contribute to sustainability.
R
R
Research
9 Research permaculture and compare it to the large-scale growing of single crops
(monoculture).
O
10Investigate one recommendation of the Rio+20: UN Conference on Sustainable
Development.
U
N
C
11
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12
2 Explain why biodiversity is important to
the traditional landowners of Kakadu.
[2 marks]
3 Recall the main characteristic the
Anangu people used to distinguished
the different habitats in their
ecosystem. [1 mark]
Apply
Ethical understanding
11Imagine you are part of an Aboriginal
group that has developed a system
of fish traps on an inland waterway.
Describe the rules you would need to
establish to ensure the benefits of the
traps were fair. [2 marks]
12Explain why it is important to manage
ecosystems sustainably. [2 marks]
PA
G
4 Imagine you are lost in the arid
Australian outback. Identify the main
abiotic factors that would make your
survival difficult. [2 marks]
FS
1 Identify one benefit that water buffalo
had on the Kakadu wetlands. [1 mark]
10To determine the size of your ecological
footprint, you need to consider how
much meat is included in your diet.
Explain how the amount of meat you
consume is related to your ecological
footprint. [2 marks]
O
Remember and understand
PR
O
Checkpoint
E
3.3
Managing sustainable
ecosystems
TE
D
5 Outline three changes you could make
to your lifestyle to minimise your
impact on Australian ecosystems. [3
marks]
EC
6 Compare the abiotic components of the
Kakadu wetlands with the ecosystems
around Uluru. [3 marks]
R
Analyse and evaluate
U
N
C
O
R
7 You read a report on the Internet that
claims regular burning of the alpine
herbfields increases the biodiversity
in these ecosystems. Describe the
evidence you would need to validate
these claims. [2 marks]
8 Outline what you think is the worst
mistake for Australian ecosystems in
the past 200 years. Justify your choice.
[2 marks]
9 Evaluate the benefits of using fire
management over reintroducing water
buffalo to Kakadu wetlands. [3 marks]
Critical and creative thinking
13Create a poster that describes the
components of an ecosystem that
would provide adequate food for a large
population of humans throughout the
year. [5 marks]
14You are to develop a new event to
promote awareness of the need to live
more sustainably. Name the event and
develop a slogan to attract interest and
highlight the key message. [2 marks]
Making connections
15Seed banks are an important way
of preserving plant species at risk
of decreasing populations or of
extinction. Research the setting up and
maintenance of seed banks. How might
seed banks contribute to sustainable
ecosystems and to biodiversity?
[3 marks]
TOTAL MARKS
[ /35]
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1 Fill in the gaps using the words in the Word Bank below:
Ecosystems are made up of __________ abiotic factors, __________ biotic factors
and the interactions between them. __________ factors, like wind speed or water
temperature, determine which __________ can survive in that ecosystem. All the
different species living in the ecosystem make up the __________.
3
FS
Some critical abiotic factors of most ecosystems include the availability of
____________, oxygen and nitrogen. These elements are maintained in an ecosystem
through the cycling of ____________. Carbon and ____________ are moved through
the cycle by two main opposing processes; ____________ and photosynthesis.
Bacteria in the soil ‘fixes’ ____________ into a usable compound, while the decay of
organic matter releases it back into the atmosphere.
PR
O
O
____________ cannot be recycled through an ecosystem, but is passed from
organism to organisms, usually through food webs, with the majority being lost to the
ecosystem in the form of heat. ____________ is vital for converting solar energy into
the chemical energy stored in ____________ molecules, which can then be used by
most organisms.
review
G
Carbon
Community
Living
Management
Matter
Organisms
Oxygen
Photosynthesis
D
Sustainable
Energy
Glucose
Nitrogen
Non-living
Population
Respiration
PA
Abiotic
TE
Word bank
E
Changes to abiotic or biotic factors can affect a ____________. Human intervention
can have positive or negative effects on ecosystems. Indigenous land ____________
practices, such as regular burning, are being reintroduced to successfully manage
____________ ecosystems.
Chapter
R
EC
Recall that ecosystems consist of
interdependent biotic communities
and abiotic components of their
environment
C
O
R
2 Identify three abiotic features of a
terrestrial ecosystem and three abiotic
features of an aquatic ecosystem.
[3 marks]
U
N
3 Identify a way in which living things
change the abiotic factors in their
environment. [1 mark]
4 Outline the major biotic and abiotic
factors that influence the size of the
human population. [2 marks]
5 Evaluate the ways in which an
ecosystem is similar to a school.
[2 marks]
Outline how matter such as
nitrogen, carbon and oxygen, is
cycled through ecosystems
6 Explain the role of decomposers in
ecosystems. [1 mark]
7 Explain why the cycling of oxygen and
carbon are so closely linked. [1 mark]
8 Compare and contrast the cycle of
matter with the flow of energy through
an ecosystem. [2 marks]
Describe how energy flows
through ecosystems via food webs
9 Identify and explain the main process
that results in energy being available to
communities. [3 marks]
10Outline how food webs are linked to
the flow of energy through ecosystems.
[2 marks]
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3 REVIEW
CHAPTER
11A bushfire burns most of the grass
away, but the gum and wattle trees
survive and quickly sprout new leaves.
Use the food web in Figure 3.54 to
answer the following questions:
c Identify the type of competition
experienced by kangaroos, wombats
and crickets. [1 mark]
d Evaluate whether the loss of grass
will affect the gum and wattle trees.
Explain your decision. [2 marks]
a Predict the initial change to the
cricket population. How will this
impact the kookaburra population?
[2 marks]
PR
O
O
FS
b Evaluate whether the loss of grass
will affect the dingo population.
Explain your decision. [2 marks]
Dingos
E
Echidnas
G
Termites
PA
Frill–necked
lizards
Wombats
D
Kangaroos
Wattle trees
Grasses
EC
Figure 3.54 An Australian food web.
O
R
R
Analyse how changes in biotic
and abiotic components of an
ecosystem affect populations of
organisms
12Compare the population changes likely
to occur because of an introduced
herbivore (such as a rabbit) with an
introduced carnivore (such as a fox). [2
marks]
13Describe the method of an investigation
that could determine whether
the spread of cane toads through
the Kakadu wetlands is affecting
biodiversity. [5 marks]
C
N
U
Crickets
TE
Eucalyptus
tree
Kookaburras
14Using a specific example, explain how
a change in an abiotic factor can affect
the population size of a particular
species. [2 marks]
15Investigate how models can be used
to predict changes in populations due
to environmental changes like natural
disasters or the introduction of disease.
[5 marks]
Research how Aboriginal and
Torres Strait Islanders use their
knowledge to conserve and
manage their environment
16Identify one land use practice of
Australian Aboriginal or Torres Strait
Islanders that has helped manage local
ecosystems yet meet human needs.
[1 mark]
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Biological control
Ecological footprint
G
Scientists use modelling to calculate
the area of land needed to produce all
the resources you use and dispose of
all your wastes. What lifestyle factors
do they consider when constructing
these models? What things can you do to
reduce your carbon footprint?
R
R
EC
TE
D
Australian native plants and animals
adapted to life on an isolated continent
over millions of years. Since European
settlement, native animals had to
compete with a range of introduced
animals for food, habitat and shelter.
Some native species also had to face new
predators. Rapid changes in land use,
such as increased crop growing areas,
affected soils and waterways. Research
the meaning of the term ‘biological
control’. Find some more Australian
examples of successful and not-sosuccessful examples of biological control.
E
PR
O
by building an ark. The Frozen Ark
Project is a modern-day project named
after this story. What is the Frozen Ark
Project? What are its goals? How is it
working towards achieving them?
PA
Research
Choose one of the following topics for a
research project. Some questions have
been included to help you begin your
research. Present your report in a format
of your own choosing.
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Frozen Ark Project
Wildlife crossings
A variety of strategies have been
implemented around Australia to reduce
wildlife road deaths and assist animals to
cross safely. What are overpasses? What
are underpasses? What types of animals
would use each? How effective are they
at reducing road deaths? Have other
strategies been implemented? Which is
the most effective?
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Reflect
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C
In the story of the floods in the Bible,
Noah protected and conserved animals
Key words
adaptation
adenosine
triphosphate (ATP)
autotrophs
balance
biodiversity
biogeochemical
cycle
capture–recapture
cellular respiration
chloroplasts
commensalism
competition
denitrifying bacteria
decomposers
dynamic equilibrium
ecosystem
enhanced
greenhouse effect
eutrophication
heterotrophs
intraspecific
interdependence
interspecific
line transect
mutualism
nitrogen fixers
parasitism
photosynthesis
population
population dynamics
predator–prey
quadrats
starch
sustainability
symbiosis
respiration
work
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21Do you think modern technology
has made it easier or harder to live
sustainably? Explain. [3 marks]
TOTAL MARKS
[ /50]
FS
19Explain why it is far more difficult to
maintain a sustainable lifestyle over a
longer period of time than for a short
interval. [2 marks]
20Explain how you think a belief system
contributes to the way people manage
their ecosystems. [2 marks]
Evaluate some examples of
strategies used to balance human
activities and needs in ecosystems
with conserving, protecting and
3 REVIEW
CHAPTER
maintaining the quality and
sustainability of the environment
17Indigenous people in Kakadu and
around Uluru use burning to manage
their ecosystems. Analyse the benefits
and risks of using deliberately lit fires
in ecosystem management. [2 marks]
18Evaluate the benefits of the Working on
Country program. [2 marks]
Me
My world
1 What new science skills have you
learned or improved on in this chapter?
2 What was the most surprising thing
that you found about the flow of
energy and matter in ecosystems?
4 Why is it important to understand the
role of energy in ecosystems?
5 Why is it important to appreciate the
interdependence of organisms in an
ecosystem?
3 What were the most difficult aspects
of this topic?
My future
6 Why is the way humans interact with
overmatter
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FS
3
PR
O
MAKING
C O NNE C T I O NS
PA
Field trip
G
E
Figure 3.55
C
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TE
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The abiotic features of the environment
determine the vegetation in an ecosystem.
The vegetation, as the basis of most food
webs, then determines which other species
can survive there.
Choose an ecosystem such as a
woodland, grassland or rainforest. After a
short study of the vegetation, measure the
abiotic factors and make a conclusion about
how they determine the type and height of
the vegetation. You will need the following
materials and equipment:
U
N
• thermometer (for temperature)
• wet/dry thermometer (for humidity)
• anemometer (for wind speed)
• light meter (for light)
• rod (for measuring soil depth)
• cobalt chloride paper (for soil moisture)
• pH paper (for soil pH)
1 Observe the plants around you.
Describe what you see. You could
take photos, draw diagrams or write
descriptions.
2 Examine the leaves of the plants.
List three of their characteristics
and give a reason why the leaves
possess this feature.
3 Choose one species of plant. Record
its common name, its scientific
name and if possible the family of
plants to which it belongs. Sketch
a leaf of this plant or take detailed
photographs.
4 Describe how your chosen plant
is adapted to the conditions in the
ecosystem.
5 Measure the abiotic factors shown in
Table 3.6 for your chosen ecosystem.
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6 For each observation and
measurement you made, analyse
and evaluate its significance. It
might be appropriate to research
and analyse the history of the area
you are studying.
Table 3.6 Abiotic factors in an ecosystem.
Abiotic factor
Reading
Temperature
Wind speed
Humidity
Light intensity
7 What conclusion can you make about
the effects of the abiotic factors
that you have measured on the
vegetation in this ecosystem?
Soil depth
Soil colour
Soil moisture
TE
D
PA
G
E
PR
O
O
FS
Soil pH
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N
C
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R
R
EC
Figure 3.56
Figure 3.57
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