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Chapter 9 Ecosystems
Unit 9.1
1
Environment
2
The living organisms, the physical surroundings and all the living and non-living
factors that make up the environment
3
Any five of: water, air quality, the amount of light, temperature, wind, soil type,
humidity of the air, tides, waves, lightning and fires
4
Competition, predation, mutualism, parasitism, commensalism
5
Birds and mammals are endothermic, whereas reptiles are ecothermic. Endotherms
can generate enough heat to keep a constant level of activity despite outside low
temperatures, whereas the activity of ectotherms slows in colder weather because
the chemical reactions are slower at lower temperatures.
6
Some species, such as grass trees, flower more readily after a fire. Some plants
release their seeds only after a fire. Many hakeas, banksias, casuarinas and
melaleucas do this. Some plants, such as wattles, have seeds that germinate much
better following a fire. Fire can encourage some seeds to germinate. It also can
encourage seed release.
7
a Any body part that helps an organism to survive
b Any feature of the way an organism’s body works that helps it survive.
c Any feature of an organism’s habits, actions or way of life that helps it survive
8
These animals are pollinators of flowers. This means the flowers are able to
produce seeds and carry on the next generation.
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9
Tabulated answer (see below)
10 Eucalypt depends on abiotic factors such as sunlight, water, carbon dioxide to
make food by photosynthesis. Eucalypt depends on biotic factors such as birds
eating insects which were feeding on leaves, and on birds and insects to pollinate
flowers.
11 A community is part of an ecosystem—the living organisms. The rest of the
ecosystem includes the non-living surroundings as well as all the biotic and abiotic
factors that affect organisms.
12 a Biotic: parents for food and shelter, farmers to raise food animals like chickens,
market gardeners for food plants like lettuce, plants for oxygen, scientists to fight
diseases, doctors to cure illness, etc. Abiotic: sunlight affects food plants, rainfall
affects food plants and animals, temperature affects amount of disease causing
bacteria and fungi, fires affect survival, wind affects amount of pollen and dust in
the air, wind strips soils and reduces food production on farms.
b Tabulated answer (see below)
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13 Birds and mammals are endothermic; reptiles and frogs are ectothermic. The Arctic
and Antarctica are extremely cold and would be a difficult place for an animal to live
if it could not produce its own heat. Reptiles and frogs would find it extremely
difficult to find a place where they could absorb heat from the surroundings. Their
body temperatures could fall to freezing and they could freeze to death.
14 Tabulated answer (see below)
15 The flagellates are actually the decomposers. They live inside the termites.
16 Depends on student answer
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Unit 9.2
chlorophyll
1
carbon dioxide + water
→
sugar + oxygen
sunlight
2
a Consumers
b Herbivores
c Carnivores
d Decomposers
e Scavengers
3
a Biodiversity
b Conservation
c Keystone species
d Ecological footprint
4
Producers
5
Arguments in favour are: compassion, cultural value, economics and survival.
6
It is the process that produces most of the food in nearly all ecosystems (apart from
a few ecosystems that are based on chemosynthesis, such as around ‘black
smokers’ at the bottom of the ocean).
7
They break down the dead bodies and wastes and recycle material for the
producers to re-use. They are vital to keep the ecosystem functioning or we would
run out of resources.
8
Energy enters an ecosystem as sunlight. This is then converted by plants into
chemical energy contained in food materials. Plants then use this food to make new
cells, or they use it in respiration. Most of it is used in respiration. There are further
energy losses along food chains.
9
Biodiversity means the range of different species in a community. High biodiversity
means a large number of different species in an ecosystem. Having many different
species makes an ecosystem more stable and less likely to be affected by
environmental changes.
10 One source of income from ecosystems is tourism. Another source of income from
native species is from those that are farmed or cropped. Many drugs have been
produced from plants that were previously not used by humans for anything. Also
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certain animals could be possible biological control agents in the future. Many
animals and plants in the future may be used for cross-breeding experiments to
improve the health of our existing farm animals and crops.
11 a Leaf miner, leaf blister caterpillar or bee
b Any of those in answer a above
c Praying mantis. Any animal other than those in answer a
d Honeyeater, peregrine falcon
e Eucalypt → honeyeater → peregrine falcon
Eucalypt → leaf-miner → wasp → honeyeater → peregrine falcon
Eucalypt → bee → honeyeater → peregrine falcon
f
Same as answer e
12 a Honeyeater, rainbow bird, brown flycatcher
b Praying mantis, wasps
13 a Second order
b First order
14 The food chain:
eucalypts → bee → rainbow bird → peregrine falcon will look something like the
pyramid of biomass shown here.
15 1 energy unit
16 a Leaf hoppers may increase in numbers as there is now more food available, so
more can survive.
b Wasps may increase as the leaf hoppers increase, providing more food for the
wasps so more of them can survive. (This would depend on how successful they
are at catching the extra hoppers, as honeyeaters also have more food available
now.)
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c Honeyeaters may increase as their food, the leaf hoppers, have increased. (This
depends on how successful the wasps are at catching the extra leaf hoppers,
and how much of the honeyeaters’ diet is the leaf hoppers.)
d Beetles could be relatively unaffected, depending on how quickly the wasp
population rises. If there is a large increase in wasp numbers, more beetles may
be eaten by the extra wasps.
17 Matter recycles. The same atoms (matter) flow again and again through the
ecosystem. Energy does not recycle. It is progressively lost at each step along a
food chain.
18 If they are photosynthetic producers, there is not enough light for photosynthesis,
so they could not make food materials for themselves and they would die.
19 There are many other uses for a forest:
•
tourism earns income
•
new drugs may be found in forest plants
•
provides breeding stock for producing new food plants
•
provides habitat for other species
•
produces oxygen
•
soaks up excess carbon dioxide to help control global warming.
20 Consider a particular mass of wheat. If the wheat was fed to cows, about 90% of
the energy in the wheat would be used up in the cows in maintaining themselves.
Only about 1⁄10 of the energy would end up in meat. So if humans ate the wheat,
instead of the cow, about ten times as much energy would be available to humans.
Therefore it is more efficient to feed people on plants than on cows.
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Unit 9.3
1
Oil glands in the leaves, stringy bark
2
Drought: death, migration, erosion of soil by wind. Flood: death, erosion of soil,
rapid animal and plant population increases in drier places.
3
Land clearing for agriculture or housing, logging and mining
4
Examples include: rabbits, foxes, goats, lantana, blackberry.
5
a DDT: killing many predatory birds like eagles
b Minamata disease caused by mercury wastes
6
The pest becomes resistant to the pesticide, and so stronger and stronger doses
are needed to kill it.
7
Thick bark insulates cells, so the plant can survive the fire. The plant can sprout by
epicormic growth. Lignotubers allow survival due to heat insulation by the soil, and
the plant can regrow from the tuber.
8
Other plant species that are competing with eucalypts are killed, because other
species are not adapted to survive fires. Eucalypts regrow quickly after a fire and
also shed seeds that can germinate. The eucalypts therefore replace the other
species in the area.
9
Plants die and so the soil is not held together by the trees’ roots. The soil can
therefore be eroded by wind or water.
10 Killing more animals than the population can replace by its normal breeding cycle
will result in a decrease in the population. If it is a large enough drop, the population
could become extinct.
11 Herbivores cannot survive without the native plants on which they feed. Clearing
the plants for farming also causes a decline in the populations of carnivores that eat
these herbivores.
12 Some of the introduced animals are predators that kill native animals. Some just
compete with the native species for food, while others destroy habitat.
13 The polar ice caps may melt, raising sea level. If the atmosphere is warming, it
could also change wind and rainfall patterns. These changes could have largescale effects on agricultural production and even result in the extinction of many
plant and animal species.
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14 Wattle seeds germinate better after a fire, and wattles can therefore quickly
increase in numbers if their germination is better than other species.
15 When Lake Eyre floods, the eggs buried in the soil hatch. Animals migrating in also
bring in eggs, as do wind and water. Plants such as plankton flourish. Rapid
increases in numbers of pelicans are evidence of the increased productivity of the
ecosystem.
16 Cumulative poisons enter food chains when herbivores feed on crops sprayed with
the pesticide. This accumulates in the herbivore because it is not removed from its
body. A carnivore will consume many herbivores, each with a small amount of
pesticide, which remains in the carnivore’s body. This builds up in the body of the
carnivore. Eventually the food chain ends in the eagle, which is accumulating all the
poison from all the levels of the food chain below it.
17 a It could cover the water and cut out light to the plants in the water, so they
cannot photosynthesise and will die from lack of food.
b Consumers will not have enough oxygen in the water because the Salvinia does
not release oxygen into the water, and the other plants that would do this are dying.
18 Having a minimum size makes sure that enough young survive to become breeding
adults. Banning removal of those in breeding condition makes sure there is a high
enough birth rate to replace those that are removed.
19 Cutting down large tracts of rainforest would reduce the amount of oxygen in the
atmosphere because forest trees release oxygen from photosynthesis.
20 One reason is that these areas provide habitat for fish, especially breeding areas
for many species. Commercial fishing supplies food for people.
21 Depends on whether they agree or disagree. Supporters claim that rising
populations require more resources and this leads to environmental damage and
over-exploitation.
Chapter review
1
Living organisms, non-living surroundings and the biotic and abiotic factors in the
environment
2
Habitat destruction, introduced species, chemical pesticides, chemical pollution,
overcropping, overpopulation
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3
a Cats, rabbits, pigs, goats, camels
b Cats kill native species. The others compete with native animals.
4
Ecosystems with high biodiversity are more stable and able to resist environmental
changes.
5
All organisms require food, and all consumers in the ecosystem need producers to
make this for them. Without the producers, all consumers would die. Consumers
depend on each other as well—carnivores need herbivores or other carnivores to
prey on. The producers and consumers need decomposers to return nutrients to
the soil for reuse by producers. So all organisms depend on each other for food.
6
Protecting ecosystems can involve methods like establishing national parks, fishing
regulations, quarantine laws, biological control and organic farming. These protect
ecosystems because they reduce the environmental impact of human activity such
as overfishing, chemical pollution and introduced species.
7
Human impacts are so great that they can destroy whole ecosystems. This affects
our own survival as well as that of all other species on the only planet we know of
that has life: Earth.
8
Termites recycle materials in dead plants, so they can be re-used to produce food
for the ecosystem. Termites live in a mutualistic relationship with flagellates, which
do the decomposing.
9
Temperature affects the rate of plant growth and therefore the amount of food
available in the ecosystem. Water and sunlight are needed for photosynthesis and
this also affects the amount of food available in the ecosystem.
10 Tabulated answer (see below)
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11 Food chains are short because there are great losses of energy at each level of the
chain—about 90% is lost at each stage. A pyramid of biomass shows how much
living matter can be supported by the available energy and this rapidly tapers off to
the peak of the pyramid.
12 Dingo and rabbit: predation. Wedge-tailed eagle and rabbit: predation. Dingo and
wedge-tailed eagle: competition. Dingo and fleas: parasitism.
13 Depends on which factors are chosen. For example:
•
Sunlight—plant needs it for photosynthesis to make its food, whereas student
does not directly use sunlight (except for vitamin D manufacture) but gains food
materials indirectly via photosynthesis.
•
Rainfall—plant needs soil moisture for cell chemistry and in photosynthesis, and
student also needs moisture for cell chemistry.
•
Parents—care for plant and care for student.
•
Pets—could scratch and injure plant and student.
14 Answers will vary.
15 a Sustainability is about whether ecosystems can continue to function.
Conservation means humans managing and protecting ecosystems so they
continue to exist.
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b Natural ecosystems are usually sustainable without human help to maintain
them. Artificial ecosystems always need help to maintain them. Some natural
ecosystems do require human help to protect them, especially from damage
being caused by human activities.
16 Our lifestyle is unlikely to be sustainable in the long term—we need to reduce our
resource use and waste production.
17 The level drops between midnight and 6 a.m. as respiration of all living things is
consuming oxygen. Level rises after 6 a.m. as the sun rises and photosynthesis
begins to produce oxygen faster than it is consumed by respiration. The level stops
rising and drops after 6 p.m. as the sun sets and photosynthesis ceases.
18 a The ghost bat and the large-eared horseshoe bat both have large ears. The
ghost bat has very large eyes and a small noseleaf, while the other bat has tiny
eyes and a large noseleaf.
b See a for the differences. The ghost bat is not as efficient at echolocation
because it has a much smaller noseleaf. The large eyes of the ghost bat suggest
that it depends a lot on its eyesight to hunt, while the other bat would have poor
vision.
19 Without photosynthesis there would be no food for all the consumers (at least in
most ecosystems, apart from a few, such as black smoker communities based on
chemosynthesis), so there would be no life.
20 Have 3 sets of 5 pots, numbered 1–5. Put 5 tomato seeds and 5 basil seeds in Pot
1, 5 tomato in Pot 2, 10 tomato in Pot 3, 5 basil in Pot 4 and 10 basil in Pot 5. Grow
for a certain time. Cut the plants off at soil level and weigh them. Compare average
plant weight of Pots 1, 2 and 3 for tomato, and 1, 4 and 5 for basil. To decide
whether competition affected a species, make the following comparison. To test
basil: Calculate whether there is any drop in average weight of basil in Pot 1
compared with Pot 4 and 5. If basil weighs less in 1 than either 4 or 5, then it has
suffered from competition from the tomato.
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21 Diagrammatic answer (see below)
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