Download Geo yr 12 - ecosystems - Homework 1

Homework 22/10/09
Ecosystems and their functioning
1. Write an extended response outlining the role of the biosphere, atmosphere, hydrosphere and
lithosphere in ecosystem functions.
An ecosystem is defined as a dynamic entity that contains the biological community interacting
with the abiotic factors within its environment. The four components of the biophysical
environment include the atmosphere, hydrosphere, lithosphere and the biosphere, and they all
perform vital roles in the functioning of an ecosystem. It is the interaction between the four
spheres that affects how a particular ecosystem develops.
The atmosphere includes the gaseous layer surrounding the Earth’s surface. It is the main source
of climatic factors that largely influences the functioning of an ecosystem. Some of the abiotic
factors including temperature and the amount of rainfall determine the nature and speed of an
ecosystem. The Rainforest biome is an example of an ecosystem that is significantly affected by
the atmosphere, as the warm, moist climate introduces a dynamic nature. These conditions
accelerate the natural processes of plant growth, the decay of dead material and the take up of
minerals. As well as controlling the climate conditions the atmosphere is also the source of the
nutrients nitrogen, carbon, oxygen and water. The atmosphere also adopts circulation patterns
that determine the spread of pollutants such as nitrogen oxide and sulphur dioxide that result in
acid rain.
The hydrosphere incorporates all the water cycles on Earth, and is closely linked to the
atmosphere. The atmosphere determines the nature of the water cycle in a particular
ecosystem, for example the polar biome consists of cold deserts with very low annual rainfall,
resulting in little available fresh water and the ecosystem functioning slowly. In stark contrast,
tropical rainforests produce large volumes of rainfall in short spaces of time, providing an
environment with high levels of biodiversity. The hydrosphere also can quickly leache soils and
erode the land, causing destruction of landscapes. Water has a high heat capacity, thus large
bodies of water, such as oceans and lakes can moderate temperatures of adjacent land mases.
The lithosphere is the rocky layer of the earth known as the earth’s crust and largely determines
the nature of soils. The capacity of the soil to provide habitats for decomposer organisms that
recycle minerals and nutrients and store water within the spaces between the soil particles,
determines the nature of a particular ecosystem. Wetlands are located in areas of non-porous
clay, as water is trapped close to or above the surface. Where as in areas of highly porous, sandy
soils, water drains away quickly leaving a dry ecosystem that is dominated by xerophytic
(drought resistant) plant communities, unless rainfall is high. Climatic factors influence the role
of soil in an ecosystem, for example in a cold climate the soil remains frozen for most of the
year. These permafrost soils of tundra ecosystems, results in virtually non-existent decomposer
activity, thus plants are unable to receive moisture. Landforms also influence ecosystem
functions as elevation can change moisture and temperature, resulting in vegetation difference.
The biosphere is the domain that comprises of all the biotic components of an ecosystem and is
found near the earth’s surface. It encompasses the atmosphere, hydrosphere and upper
lithosphere and exists in a narrow zone that extends from -200m to about 9000m above sea
level. There are two types of organisms on earth: autotrophic organisms and heterotrophic
organisms. Autotrophic organisms manufacture their own food using solar energy, water,
carbon dioxide and nutrients from the soil. Most autotrophic organisms make organic
compounds via photosynthesis and are often referred to as producers. Heterotophic organisms
are consumers as they cannot make their own food. This group includes herbivores, carnivores,
omnivores and decomposers.
The atmosphere, hydrosphere, lithosphere and biosphere, all perform vital roles in the
functioning of an ecosystem. The interaction between each affects the nature of different
biomes and the speed at which they develop.
2. Study the Geofocus box ‘Bioaccumulation’. Explain the effect of bioaccumulation on
ecosystems.
Bioaccumulation is a process whereby toxic chemicals are concentrated at successively higher
trophic levels within the food chain. These toxic chemicals which include pesticides, radioactive
materials, mercury and lead compounds, are selectively stored in biological tissue and are either
degraded slowly, or are non-degradable by natural processes. An ecosystem is a dynamic entity
that contains the biological community interacting with the abiotic factors within its
environment. Bioaccumulation would cause a negative impact on the environment, as it
becomes amplified along food chain and on a larger scale food webs. Within an ecosystem,
accumulation and amplification of toxic substances will result in an imbalance of organsisms,
and a vulnerable ecosystem.
3. Study the Geofocus box ‘Dioxin contamination leads to fishing ban in Sydney Harbour’
a) Outline the source of dioxins in Sydney Harbour.
The source of dioxins in Sydney Harbour originated, many decades ago when chemical works,
paint factories and other heavy metal industries lined the foreshore of Homebush bay. These
industries discharged large amounts of pollutants including dioxin, in the bay. The toxins have
gradually spread out of the bay in a ‘toxic plume’.
b) Explain the impact of dioxins on the functioning of Sydney Harbour.
Sydney Harbour was heavily impacted by the dioxins as the tosins have gradually spread out
across the bay, increasing dioxin levels in a range of species. This has resulted in an indefinite
ban on commercial fishing within Sydney Harbour in February 2006, as a scientific investigation
found that the high levels of dioxin in fish caught in the harbour were cancer-causing.