Download Caught in the web

Caught in the web
spider builds a web with lots of threads linked together. If
one part of the spider’s web breaks, the whole structure
is weakened. In a similar way, all the parts of nature join
together to make an ecosystem. If we break one of the
threads in the ‘web of nature’, the other parts of nature will
also be weakened. These threads of nature that hold everything
together are important to our survival. They are often invisible to
us, but if you look hard enough, you might be able to see them!
A
The Earth is alive!
Australian Aboriginals have traditionally
believed that the whole Earth is living. They
believe that animals and plants are not any
different from the rocks, mountains, Sun, fire,
water or air. After all, animals and
plants cannot survive without
these things.
The Rainbow
Serpent
(carpet snake)
is said to be
the creator
of life.
She is
responsible
for the colours
and shape of
Earth. She
called spirits to
make the
mountains,
light, water
and colour
that
brought
Mother
Earth to
life. Do you
think a
mountain or
river can be
alive?
The Sun is the source of all life on Earth.
It supplies the energy that plants use to make
their food. All animals depend on the food that
plants make for their energy.
Animals depend on rocks for shelter and a
safe home away from those who may want
to eat them. Lizards also sit on
rocks in the Sun to get warm.
Water is
essential to all
life. Animals
and plants are
mostly made
up of water.
Amazingly,
your own body
is made up of
about 70 per
cent water!
Some animals
and plants
also live
in water.
Humans are
animals too.
Often we think we
are not, but we
depend on the ‘web of
nature’ just like all
other animals.
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Science Alive for VELS Level 5
Go to worksheet 7.1:
The web of nature
Animals depend on trees
and plants. Trees and
plants provide food (fruit,
flowers and seeds) and a
home for many insects and
animals. Plants also make
some of the oxygen that we
need to breathe.
Many plants and animals have
relationships that help each
other. In this example, a bee is
pollinating a flower so that the
flower can make seeds. The
seeds will grow into new plants.
REMEMBER
1. What is an ecosystem?
2. What does biotic mean?
3. Give two examples of biotic factors in an
ecosystem.
4. What does abiotic mean?
5. Give two examples of abiotic
factors in an ecosystem.
6. Why is the Sun said to be the
source of all life on Earth?
THINK
7. Explain the term ‘web of
nature’ in your own words.
8. How do insects that live on the
tree in the picture depend on
the water that is in the river?
9. How do humans interact with
the other living and non-living
things in the ecosystem shown?
10. Choose a human activity that may
cause damage to the web of nature.
Explain how the web may be
weakened by this human activity.
11. Is the ecosystem shown at left
connected to other ecosystems
nearby? Explain.
IMAGINE
12. Imagine that you are one of the
animals, plants or abiotic features of
the ecosystem shown. Write a story of
a day in your life that describes your
interactions with other species and
the non-living things. For example,
you may be the water that animals drink,
part of you evaporates and rains down on other
species, you soak into the soil and get drawn up
by a tree, and so on.
Many animals, like ants and worms,
live in the soil. Worms also use the soil
as their food. Plants can get nutrients
from the soil through their roots. They
also use the soil to support themselves.
Living organisms interact with each other in an
ecosystem. They also interact with the non-living parts
of the environment they live in. The living things in
an ecosystem are called biotic factors. They include
animals, plants, food and predators. The non-living things in an
ecosystem are called abiotic factors. These include water, rocks,
soil, the Sun and weather.
animals, plants and non-living things you
depend on for survival. Record all of the ‘things’
that you use during the day. Some of them you
will easily see — like the food that you eat.
Others, like the air you breathe, may be harder
to recognise. Set up a table to record your
results.
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7. Living together
✓ learning
Animals depend
on other animals
for food. This is
just another part
of the web.
INVESTIGATE
13. Keep a diary for a day to track how many living
I CAN:
explain the difference between biotic
and abiotic factors in an ecosystem
describe the relationships between living
things in an ecosystem
describe the relationships between living
and non-living things in ecosystems.
Who’s hungry?
ll of the animals in a rock pool need to eat. Food is where animals get the
energy they need to grow, move and reproduce. Some animals eat plants,
but many eat other animals. What do you think the animals in this rock pool are
having for dinner
Other larger fish, such as the zebra
tonight?
A
fish, may be found in rock pools.
This fish feeds only on seaweed.
Birds visit a
rock pool to feed
on fish, crabs,
shrimp,
sea urchins or
shellfish.
The octopus is an expert
hunter. Octopuses eat
fish, crabs
or shrimp.
Algae and sea plants use
the Sun’s energy to make
food. Algae and seaweed
are producers.
Sea stars eat anything they can
find. This includes crabs, shellfish
and algae. They push their stomach
out through their mouth and digest
food outside their body.
The elephant snail has a shell that
does not completely cover its body. It
hides under ledges in rock pools and
comes out at night to feed on algae.
Many animals, such as this sponge,
filter the water for plankton.
Rock pool shrimp are scavengers.
The blenny fish is a common rock pool
fish that eats other small animals,
recently dead meat or algae.
Producers
Many snails, such as the
conniwink, chiton and limpet,
eat algae. They use their
rough tongues to scrape the
algae off rocks.
Sea urchins hide during
the day and move about at
night feeding on algae.
They have spikes to stop
other animals eating them.
Producers are organisms that can make their own
food. All plants make their own food using the energy
of the Sun in a process called photosynthesis. In
photosynthesis, plants use water, and carbon dioxide
from the air, to make sugar (food) and oxygen.
To do this, the plant also needs a green pigment
called chlorophyll. This is usually found in the leaves.
The food made by plants becomes food for animals.
The chemical word equation for photosynthesis is:
carbon dioxide + water
sunlight
sugar (food) + oxygen.
chlorophyll
Consumers
Consumers are organisms that rely on
other organisms for their food. Consumers
feed on plants or other animals. The food is
used as the material for growth and to
release energy for living. The energy in
foods is released in a process called
respiration. Respiration takes place in every
living cell. Plants also use respiration to release
energy from the food they have made. Respiration is
a chemical reaction in which organisms use oxygen
and sugar to produce carbon dioxide and water.
Energy is released during the reaction. The chemical
word equation for respiration is:
energy released
oxygen + sugar
Sea anemones have sticky
tentacles that catch
anything that floats by in
the water. This includes
fish, algae, microscopic
animals, and plants
called plankton.
The dog whelk is a snail that
eats other snails. It drills a
hole through the snail’s shell
with its rough tongue and
sucks out the insides.
carbon dioxide + water.
Meat or vegetables?
Carnivores are animals that eat
only the meat of other animals. In
a rock pool, these include the dog
whelk and the octopus. Animals
that eat only plants are called
herbivores. The elephant snail and
the green turban snail are
examples of herbivores. Some
animals have a more balanced diet
and eat both animals and plants.
These organisms are called
omnivores. The sea star is an
omnivore in the rock pool.
The green turban is a snail that
feeds on larger seaweeds.
Crabs feed on dead or decaying material in rock pools. Animals that feed on
dead and decaying material are called scavengers. They eat anything they can
find. The decorator crab covers itself in seaweed for camouflage.
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7. Living together
Food chains
Food webs
A food chain shows how the energy
stored in one organism is passed to
another. Each organism depends
on the one before. All food chains
start with a producer, such as algae.
The producer absorbs its energy
from the Sun and provides the
nutrients and energy that other
animals need. Herbivores that eat
the plants, such as the green
turban snail, are called first-order
consumers. Carnivores that eat
first-order consumers, such as the
dog whelk, are known as secondorder consumers. The seagull is a
third-order consumer because it
eats the second-order consumer.
A food chain can be represented
by a simple diagram.
Many animals eat more than one type of food. This means that they are
in more than one food chain. Joining a number of food chains together
produces a food web. Note that some animals, such as the seagull, may
actually be in more than one level, depending on which chain you follow
to the top. A food web also has decomposers. Decomposers are
organisms, such as bacteria, worms and fungi, that break down dead
animals and plants. The nutrients in the dead animals and plants are
recycled back into the food web.
Energy
Secondorder
consumer:
dog whelk
Animal waste and dead organisms
Third-order
consumer:
seagull
Octopus
Crab
Zebra fish
Green
turban
snail
Shrimp
Energy
Blenny
First-order
consumer:
green
turban snail
Energy
Seaweed
and algae
Dead and
decaying material
Producer:
seaweed
Decomposers
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Science Alive for VELS Level 5
An energy
pyramid
REMEMBER
Producers absorb the Sun’s
energy during photosynthesis
to make sugar. Some of the
Sun’s energy is stored with the
sugar. When consumers eat
producers, the energy is
passed up the food chain.
However, some of this energy
appears to be lost at each link
in the chain. But the energy
cannot just disappear. Instead,
it is transferred to the
surrounding environment as
heat, wastes, and even sound.
This means that only a small
amount of the Sun’s energy
makes it to the top consumer.
For energy to reach the
animals at the top of the food
chain, there must be many
plants at the bottom of the
chain. This means that a food
web rarely has more than six
trophic levels. At each level
there are fewer animals of
each type because there is less
energy available. This is
shown in the energy pyramid.
Dog whelk
Limpets
1. What are producers?
2. From where do producers get their energy?
3. What are consumers?
4. How do consumers release energy from the food
they eat?
5. Write an equation for respiration.
6. What does a decomposer do?
7. What happens to the amount of energy available
to organisms as it moves through an energy
pyramid?
THINK
8. What is the difference between a food chain and
a food web?
9. Use examples to explain the difference between
herbivores, carnivores and omnivores.
10. Give two examples, from the rock pool, of
predators and prey.
11. What would happen to the animals in a rock
pool if the seaweed and algae died?
12. What is the advantage of animals having more
than one food source?
SKILLBUILDER
13. Julie and James were studying animals in their
local park. They made the following observations:
• Grasshoppers eat grass.
• Mice eat grass seeds and grasshoppers.
• Small birds eat grasshoppers.
• Snakes eat mice and small birds.
• Kookaburras eat snakes.
Energy
Construct a food web using this information. The
producers should be at the bottom.
(a) Which organisms are producers?
(b) Which are first-order consumers?
(c) Which is a second-order consumer only?
(d) Which is a second- and third-order
consumer?
(e) Which is a herbivore?
(f) Which is an omnivore?
(g) Which organisms compete for food?
(h) Which have more than one food source?
(i) What would happen if the snakes died out?
Energy
1 Octopus
Energy
2 Larger fish
6 Small fish
500 Plants
This food chain has four trophic levels.
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7. Living together
✓ learning
Seagull
I CAN:
describe how plants and animals gain
their energy
describe how plants and animals
depend on each other in a food chain
explain how organisms depend on
each other in a food web.
Natural recyclers
ross! Worms, maggots and bacteria! To most people these creatures are
disgusting. But where would we be without them? These tiny organisms
actually help to clean up the environment. They are the decomposers that recycle
dead and decaying material. Decomposers can usually recycle anything that was
once living. Material that can be broken down naturally is called biodegradable.
Decomposers make the nutrients in dead things available for other plants and
animals. Without them, the whole world would have dead animals lying around
everywhere!
G
Flies and maggots
Flies lay their eggs on dead and decaying animals. The
eggs hatch into larvae that are called maggots. The
maggots can quickly eat away
large parts of a dead animal.
The maggots grow up to
become flies, which lay eggs
somewhere else, or become
food for other animals. This
recycles the nutrients from
the dead animal back into
the ecosystem.
Worms
Worms are very effective recyclers. Worms eat just
about anything and can do so quickly. They are
especially good at recycling
our food waste. Worms are
found underneath dead
organisms in the soil.
They feed on animal
and plant remains,
recycling them into
nutrients for plants.
Fungi
Bacteria
Bacteria can grow on anything — dead or alive. They
grow and reproduce very quickly. Bacteria reproduce by
simply dividing in half.
Bacteria feed on decaying
material to help break it down
and recycle nutrients for other
animals. The photograph of
the bacteria shown was taken
under a microscope.
Mushrooms and toadstools are fungi that feed on dead
material. Another variety of fungi is called mould and
looks ‘fuzzy’. Fungi grow microscopic threads into the
food they are feeding
on. These threads
help to break down
the dead organism.
Fungi may become
food for other
animals, or they may
decay. This allows the
nutrients to be
recycled back into the
ecosystem.
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Science Alive for VELS Level 5
Go to worksheet 7.3:
Decomposers
The amazing worm farm
About 60 per cent of our household rubbish can be used as worm food. Worms will eat just about
anything that was once living, including kitchen scraps, garden waste and manure. They love pizza and
will even eat the box it comes in! Worms can eat about half their body weight in food each day. We can use
a worm farm to feed our once-living rubbish to worms. This is how a worm farm works.
The lid has ventilation holes to let air in.
The holes are small so
that flies and
insects can
not get in.
The top level is still empty.
There are holes between each
level to allow the
worms to move
up when the
level below is
full.
A bedding of
shredded paper,
manure, leaf
compost, or a
mixture of these,
is added first.
The bedding must
always be kept
damp.
Food scraps are added on top of the
bedding for the worms to eat. A sheet of
newspaper or hessian is put over the top
of the food to keep it dark.
REMEMBER
1. What does biodegradable mean?
2. Name two types of
biodegradable waste.
3. Name two types of nonbiodegradable waste.
4. What are the four types of animal
that decompose dead things?
5. Why are decomposers also called
natural recyclers?
6. Why are worms such good
recyclers?
THINK
7. Both bacteria and maggots are
decomposers that feed on dead
material. But they are also
different types of organism.
Compare the size and
reproduction of bacteria and
maggots.
Liquid runs into the tray on the
bottom and is known as ‘worm
wee’. It makes an excellent liquid
fertiliser for plants.
8. Explain why a worm farm is a
useful way of disposing of some
household rubbish.
9. Why are paper bags better for
the environment than plastic
bags?
You could compare garden
worms with some worms
purchased at a garden centre.
DESIGN AND CREATE
12. Build a worm farm for your
class. This could be used to
recycle your class’s lunch waste.
Using an appropriate search
engine, you should be able to
find a simple design on the
Internet.
INVESTIGATE
10. Do some research to find out
more about worms. This could
include information about their
body structure, how they
reproduce, what they do or do
not like to eat, and their
behaviour.
11. Some types of worm are good
recyclers and others are not.
Design an experiment to test
how good different worms
are at recycling food scraps.
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7. Living together
✓ learning
Worms are placed in
the bedding.
The worms turn
the bedding and
food scraps into
compost. This is
the nutrient-rich
‘worm poo’.
I CAN:
describe how animals and plants
are recycled
explain the difference
between biodegradable and
non-biodegradable
describe how a worm farm works.
Life in the desert
ife is rather tough in a desert environment. Desert plants and animals face
extremes of temperature, food shortages and a lack of readily available water.
To survive, they have to adapt to these harsh conditions.
L
Animal survivors
Plants and animals
of the Australian
desert
The bodies of desert creatures have
adapted (evolved) to help them
survive. Many are pale in colour, to
reflect the heat. Some desert
animals, such as reptiles, can vary
their body temperature dramatically
to cope with extremes of
temperature. Some desert animals
have very long legs to increase the
distance between their bodies and
the hot sand. Others have thick,
leathery skins or hard, waxy shells to
help them retain water, or thick fur
or feathers to insulate their skin
from extremes of temperature.
Staying cool
When it gets too hot, most desert
birds look for shade. Some take off,
to drift on the cool thermals that
blow high above the hot sands.
Many desert animals dig deep
burrows in the ground, where they
stay during the heat of the day,
coming out to hunt at night. Desert
storks and vultures urinate on their
legs. The evaporating urine cools
the skin, and the cooler blood then
flows back into the body. Some
creatures hop to minimise contact
with the hot sand or, like lizards,
they run extremely fast.
Food and water supplies
Most large desert animals survive
because they are herbivores. They
obtain moisture from the plants
they eat. Others, like scorpions, get
their moisture from their prey or
from dew. The camel stores fat in
its hump, and can go for days
without drinking. The scarab
beetle solves the problem of a
scarce food and water supply by
eating animal dung!
Budgerigars feed on seeds
produced by native plants.
They are nomads, and in
large flocks of a few
thousand or more they
follow the flowering cycles.
Spinifex leaves roll into tight
cylinders during the hot
desert day to reduce the
surface area exposed to the
sun. Spinifex roots spread
deep and wide to pick up both
ground and surface water.
Death adders are
commonly found at
night, soaking up the
heat from roads.
The spinifex hopping mouse does not
sweat, its droppings are dry and its
urine is very concentrated. A female
feeds her young on concentrated milk
and drinks their urine.
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Honey ants store food and
water in their abdomen, which
swells up like a plastic bubble.
When food is scarce, they vomit
up the nectar to feed the colony.
Go to worksheet 7.5:
Create a desert animal
Plant survivors
Desert plants are made up of
those that have adaptations for
long-term desert survival, called
perennials, and those that have a
very short life cycle, called
ephemerals. The seeds of desert
ephemerals lie dormant for a long
time, waiting for rain. After it
rains, they grow rapidly, living
their whole life cycle in a few days.
Some desert perennials — for
example, America’s mesquite tree
The camel has a double row of
eyelashes on each eye to keep
out glare and grit. It stores
energy as fat in its hump and
can swallow about 100 litres
of water at a time.
or Australia’s river redgum —
have very long root systems, often
stretching down to the watertable.
Others, such as succulents, have
shallow but widely spread root
systems so they can soak up and
store lots of water when it rains.
Many perennials have small leaves,
often waxy, to reduce loss of
moisture through transpiration.
Some have no leaves at all — just
thorns and spikes.
REMEMBER
1. Why is survival a problem in a
desert environment?
2. Describe the behaviours of
two animals that help them
survive in the desert.
3. Explain the difference
between perennial and
ephemeral plants.
UNDERSTAND
4. Copy and complete the
following table in your
notebook.
Mulga have specially shaped
leaves and branches that
funnel rainfall to the base
of the tree.
Plant or animal
feature
How it helps
survival
Small, waxy leaves
Termites live in tall mounds
of clay. They are protected
inside the mound from the
hot, dry desert winds.
Large ears
Pale colouring
Hardy seeds
Thick fur
COMMUNICATE
5. Conduct some research to find
out more about one of the
following desert creatures or
plants — particularly how it has
adapted to its environment:
fennec fox, pup fish,
roadrunner, tarantula, Mitchell
grass, Sturt’s desert pea, prickly
pear. Create a colourful poster
that includes photographs or
drawings, a location map and
interesting statistics.
Rock wallabies rest in shady caves and
crevices during the hottest part of the
day. When no grasses are available,
they can eat leaves, bark and roots.
DESIGN AND CREATE
6. Design and label the perfect
desert animal. Consider how
your animal:
• survives hot days and cold
nights
• obtains food and water
• protects itself from
predators.
South Australia’s desert
spadefoot toad hibernates in
burrows for most of the year,
coming out to breed and lay
eggs only when it rains.
The marsupial mole is blind
because it has no need for eyesight
when living underground. It moves
underground by ‘swimming’
through the sand.
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7. Living together
✓ learning
Bilbies always stay close to one of several
burrows they dig. These protect them from
desert heat and predators.
I CAN:
see how animals and plants have
adapted to a desert environment
understand how a desert changes
over time
conduct research about animal
adaptations.