2005 HSC Notes from the Marking Centre Earth and Environmental Science

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2005 HSC Notes fromthe Marking CentreEarth and
Environmental Science
STANSW Meet the Markers
David Tweed, Penrith Anglican College
d.tweed_at_pac.nsw.edu.au Fiona Branch, Sydney
Grammar, fhb_at_sydgram.nsw.edu.au
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General Comments

• 1131candidates attempted the Earth and
  Environmental Science examination.
• The most popular electives were Introduced
  Species and the Australian Environment (76) and
  Oceanography (10).

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Content

• knowledge, understanding and skills developed
  through the study of discrete sections should
  accumulate to a more comprehensive understanding
  than may be described in each section separately
• It is important to understand that the
  Preliminary HSC course is assumed knowledge for
  the HSC course.

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Skills 9.1

• at least one question in Section 1 Part B focused
  on the mandatory skills content in Module 9.1.
  Candidates who had actively planned and performed
  practical experiences clearly demonstrated a
  deeper knowledge and understanding of the content
  described in this module.

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Depth of treatment

• Candidates need to be reminded that the answer
  space provided and the marks allocated are guides
  to the maximum length of response required.
• Candidates should use examination time to analyse
  the question and plan responses carefully,
  working within that framework to produce clear
  and concise responses. This may include the use
  of dot points, diagrams and/or tables, and avoids
  internal contradictions. This isparticularly so
  in holistic questions which need to be logical
  and well structured.

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Better Responses

• Better responses indicate that candidates are
  following the instructions provided on the
  examination paper. In these responses,
  candidates
• show all working where required by the question
• do not repeat the question as part of the
  response
• look at the structure of the whole question and
  note that in some questions the parts follow from
  each other ie responses in part (a) lead to the
  required response in part (b) etc
• use appropriate equipment, for example, pencils
  and a ruler to draw diagrams and graphs.
• (A clear plastic ruler would aid candidates to
  plot points that are further from the axes and
  rule straight lines of best fit.)

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Scaling of EES
http//www.uac.edu.au/pubs/pdf/2005-Table-A3.pdf
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b) Oceanic crust is denser and thinner than
continental crust. c) The collision of two
plates results in Compressive Forces that cause
faulting, folding and metamorphism of rocks
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17 a) Pyroclastic flow, Lahar.
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b) Sumatra is Located near a subduction zone. The
subduction of the indo Australian plate beneath
Sumatra causes the production of magma due to
partial melting. This magma creates the composite
volcanoes like Toba.
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18 a) Radon gas meters measure the level of radon
gas released from faults. An increase in the
level of radon detected could indicate an
increase in earthquake activity, and thus prove
useful in predicting earthquakes.
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b) Current technology has many problems
predicting earthquakes. Improved methods would
lead to more accurate early warning systems and
evacuation plans decreasing the loss of life and
the destruction of infrastructure.
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19 Heat generated from the base of the mantle
circulates in convection currents. The mantle
material becomes less dense and rises when
heated. The horizontal motion of the convecting
mantle results in friction with the plates
producing basal drag. This drives the plates in
the direction of the convecting currents. DIAGRAM
of convection Cell
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20 (a)
Time Division Length of time (Ma)
Proterozoic 1950 Ma
Archean 1300 Ma
Cenozoic 50Ma
Triassic 40 Ma
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(b)
Precambrian Postcambrian
Soft body parts Development of hard body parts
Simple life forms More complex life forms
Generally less predation More predation
Vulnerable to predation More protective body parts less vulnerable to predation
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• BIFs are sedimentary rocks formed of alternating
  layers of Iron oxide rich (indicating increasing
  oxygen levels) and iron oxide poor (indicating
  low oxygen concentration) high silicate
  sediments. They indicate fluctuating levels of O2
  in the aquatic environment, produced by
  cyanobacteria.
• The O2 released, reacted with the Fe2 dissolved
  in the oceans to form FeO which settled on the
  bottom of the aquatic environment. As the
  cyanobacteria populations varied so to did the
  oxygen levels and the consequent FeO levels in
  the Sediment

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(b) The media report is unreliable as the
Cretaceous environment was highly Oxygenated
supporting a wide variety of life forms that used
respiration. All the free Fe2 had precipitated
out of the ocean by this stage allowing oxygen to
enter the atmosphere, form ozone and allow
terrestrial ecosystems to develop.
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Roots/Rhizoids would only need small root hairs
as they would be mainly used for attachment to
some substrate in a swampy environment. a more
extensive root system would be required for the
absorption of water and nutrients and for
anchorage of the plant. Stem Plant stem in
water is buoyed up by the water therefore does
not require much structural material. In a
terrestrial environment the stem would need to be
strengthened by lignin/cellulose for
support. Reproduction - Sporangia would release
spores into a watery environment. on land, seeds
would be needed prevent dessication
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23 (a) Oxygen is composed of 2 atoms O2 Ozone is
a molecule combining 3 oxygen atoms O3
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(b) The general trend is a decline in Ozone over
45 years There are many fluctuations over this
time The most rapid decline is between 1980 and
1990. The levels seem to be stabilising between
1995 and 2000
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(c) Montreal protocol early signs show success
as ozone depletion stabilised. Banning of ozone
depleting substances (eg CFC Halides, Methyl
bromide) used in aerosols, refrigerants,
extinguishers. Impact on society increased
awareness, finding alternatives impacts upon
industry, decrease in skin cancer in the long
term. Impact on the environment- Increasing
levels of ozone once again, reduction in level of
UV reaching the earth. Some replacements for CFCs
are greenhouse gases creating/enhancing other
problems.
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Sewage treatment is a current method. It involves
the primary, secondary and tertiary stages of
treatment as detailed below. This is an effective
method as it removes all solid wastes, kills
bacteria, removes organic material and soluble
nutrients. It prevents the growth of algal blooms
and eutrophication and is and environmentally
friendly process. This along with the fact that
the recycled water can be returned to town
catchment water supplies used to drink, irrigate
or maintain environmental flows makes it an
effective method.
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25 An environmental flow introduces released dam
water back into the environment in cycles. This
is important as the introduction of water
stimulates breeding /dispersal of some species
and ensures biodiversity is maintained. It
allows the dispersal of organic material over
flood plains which contributes to the soils
fertility and maintains plant diversity and
health.
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26 Soils in the west are vastly older than soils
in the east. Soils in the west are also nutrient
poor ( less fertile ) compared to the soils in
the east. The age of soils affects the amount of
weathering and erosion that they have undergone.
WA soils have undergone millions of years of
leaching depleting them of any nutrients they may
have had. Soils in eastern Australia have not
gone through as much leaching so have still
retained many of their original nutrients.
Recent volcanic activity in the east has also
lead to the formation and replenishment of basalt
derived nutrient rich soil. A lack of volcanic
activity of any recency in the west means there
has been no replenishment of nutrients via
weathering and erosion of basalt.
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27 i) A table was used to present the data. It
had three columns for name, type and description
of the indigenous and non indigenous species in
the area
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(ii) This investigation was best undertaken by a
team as we needed a wider knowledge of introduced
species for identification. More people gave us a
wider knowledge and enabled us to finish the job
in a shorter time
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1. (i) Graph Q27b Abundance of species over time

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(ii) the number of species 1 increases rapidly
from 30July to 5 August2002 indicating that it
was well adapted to the environment. Between 5
August 2002 and 17 February 2003 the number of
species declined rapidly due to the a drought as
they were not adapted to the change. After that
the species that survived started to increase
slowly. Species 2 declined throughout the whole
range but were less affected by the drought, as
they were better adapted to these conditions.
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Salvinia molesta is a pond weed that was
introduced in the 1950s and escaped from fish
ponds and entered waterways Recently there has
been an outbreak of this plant in the Hawkesbury
Nepean river system. Salvinia lives in waterways
with high nutrient levels resulting from
agricultural runoff Its high reproductive
capacity means that the plant can double its
size in two days covering an area of 100km2 in
just three months. Salvinia floats on the surface
of the water preventing light from penetrating ,
and thus killing aquatic plants, reducing aquatic
Oxygen and leading to eutrophication. A number of
strategies have been implemented to control this
species. A biological control has been released
to naturally control the plant growth. A
brazilian weevil was released to burrow into the
salvinia, allowing bacterial spores to enter the
plant and kill it. This method is effective on
large outbreaks as it isnt labour intensive and
is cost effectiveonce it has been trialled and
released. This trial process is however expensive
and timely. The weevil doesnt survive in cooler
areas. So despite its success it has its
limitations as a means for control. Herbicides
have also been used to effectively control large
populations of salvinia however this process is
expensive as it is labour intensive and it also
adversely affects non target species. Salvinias
high reproductive capacity means that if only a
few plants excape the spraying then it could
quickly repopulate the area. Methods used to
control the spread of Salvinia are effective in
some ways but ineffective in others. An
integrated approach may be the best option to
control salvinia and rehabilitate the ecosystem
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d (i) European farmers introduced plants for
agriculture eg fruit trees because they had a
better knowledge of farming methods of crops
cultivated in their homeland and preferred to eat
European food types.
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(ii) The garden in photo 1 has involved the
removal of native species and their replacement
with lots of introduced species. Abiotic
characteristics that have been altered
include- Pine trees drop needles and increase
the acidity of the soil Use of excess water on
the garden or plants with shallower roots may
cause the watertable to rise and create salinity
problems. Less sunlight reaching the soil due to
more dense vegetation compared to native garden.
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(iii) The garden in photo 1 will start to die off
since the plants do not have special adaptations
to prevent water loss or conserve water. For
example the plants possess shallow roots that do
not allow them to suck up water if the watertable
drops severely during the drought or they have
large thick leaves or lots of large stomates that
cause them to loose water quickly through their
leaves. The garden in photo2 will survive since
native plants are well adapted to dry Australian
conditions. They possess smaller leaves with waxy
coatings or the trees possess deep roots that
will enable them to suck up water from a lowered
water table.