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Transcript
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.