Changes in Ecosystems

Change can occur due to: regular or predictable events such as tides and seasons sporadic (irregular) events such as floods and wildfires one-off events such as a massive oil spill that impacts on marine habitat

Displacement and loss of native species Bring in new diseases Use the same limited resources (food and shelter) and compete more effectively Change the environment Invasive Exotic Species

High reproductive rate Competed more efficiently than native species for food Replaced some native species Biological control: release of viruses (carried by mosquities and fleas) But rabbits eventually became resistant. Example: Rabbits

Extremely dangerous. It can take populations a long time to recover, if at all, especially K-selected species. Overharvesting

Dryland salinity Dryland Salinity

Greenhouse Effect

Waste Disposal

Question 1 Rabbit numbers in Metropolitan Melbourne have soared over the past two years since the drought broke. There have been two excellent seasons of rain after a fifteen-year period of below average rainfall. Rabbits cost $200 million per year in lost productivity and various control measures. a. Explain fully two reasons for the enormous rise in rabbit numbers triggered by the high rainfall. (2 marks) Rabbits are controlled by various methods such as ‘1080’, a poison used to bait carrots which, when eaten, are deadly, or biological control methods such as myxomatosis virus or calicivirus. b. Explain biological control. (1 mark) c. Hume City Council has been targeting Reserves throughout its municipality in suburbs such as Sunbury, Bulla and Greenvale. Describe a method which could be used to estimate the population of rabbits in the Reserves of Hume City Council. (1 mark)

Question 2 The Carbon Tax was introduced on 1 July About 500 Companies now pay $23 per tonne of carbon based gas produced. The Government’s aim is to reduce greenhouse gas emissions by 2020 to 5% less than the 2000 levels. a.Name two carbon based gas which contributes to the greenhouse effect. (2 mark) b. Explain the greenhouse effect. (2 marks) c. Name an alternative to fossil fuels which can be used as an energy source to produce electricity which does not produce greenhouse gases. (1 mark) d. Explain why planting trees, used for construction, would reduce the greenhouse effect. (2 marks)

Question 3 Salinity is an increasing problem in Australia, with more and more agriculutural land falling victim to this process. a. Outline the key steps involved in dryland salinity (2 marks) b. To help prevent salinity from destroying the visibility of farmland, several methods of prevailing salinity or rejuvenating the soil may be taken. Identify two of these. (2 marks) Conservation of species is very important in maintaining the stability of ecosystems. c. List two ways in which species can be saved. (2 marks) Logging is still occurring in many parts of the world. However, many logging companies are now changing their practice to make the industry more sustainable. d. Identify two ways in which a logging company may argue that they are acting in a sustainable manner. (2 marks) In Tasmania, The Tabune National Park has what is known as a ‘skywalk’; a walkway supported by beams and wires, situated many metres above the forest floor. e. Explain how this is considered ecotourism. (2 marks)

Question 7 Changes to ecosystems by means of human activity can be seriously damaging. Rivers around the world have to a large extent been dammed, which causes floodplains to rapidly disappear due to sewage and waste disposal. Floodplains are extremely important in maintaining the balance of nutrients in bodies of water because nitrogen fixation and denitrification can only occur in oxygen-free environments. a. What process is occurring during nitrogen fixation? (1 mark) b. What process is occurring during denitrification? (1 mark) When water contains high levels of nitrogen, which is extremely common now due to the presence of nitrogen in fertilizers, organic matter from human waste and surface run off, the nitrogen moves into a floodplain area, and nitrogen can be released back into the atmosphere. However, if this doesn't occur, then excess nitrogen will remain in the water and because it is a limiting factor for algae it will cause big algal blooms and eutrophication. c. What is meant by the term limiting factor? d. What is the effect will algal blooms and eutrophication have on other organisms.