Year 8 Science · Unit 1 · Lesson 25
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Learning Goals
Read the graph
Estimated causes of Australian terrestrial mammal extinctions since 1788
Data: Woinarski et al. (2015), The Action Plan for Australian Mammals, CSIRO Publishing.
(a) Which two causes together account for 85% of Australian mammal extinctions? What does this tell us about the most important areas for conservation action?
(b) Overexploitation accounts for 10% of extinctions. Suggest one specific example of overexploitation that may have contributed to this, and explain why it is hard to reverse once it begins.
(c) The graph shows data from 1788 to 2015. Predict how the bar for "climate change" might look if a new bar were added for extinctions projected between 2015 and 2050. Justify your prediction.
Real-world context
Tasmanian devils (Sarcophilus harrisii) are the world's largest carnivorous marsupial. Since the 1990s, a contagious facial tumour disease (DFTD) has spread through the Tasmanian devil population, causing declines of up to 80% in many areas. Because DFTD is spread by biting during feeding and mating, high-density populations suffer the fastest spread. Scientists at the Save the Tasmanian Devil Program have established insurance populations on mainland Australia and on Maria Island, Tasmania, using captive-bred devils that are DFTD-free.
(a) Tasmanian devils are apex predators in Tasmania. Using your knowledge of food webs and biodiversity, explain what might happen to the Tasmanian ecosystem if Tasmanian devil numbers continue to decline sharply.
(b) The Maria Island insurance population was deliberately kept separate and isolated from the mainland. Using your understanding of conservation strategies, explain two reasons why this isolation was important.
1. Explain the difference between endemic and invasive species. Give one Australian example of each and explain why invasive species pose such a serious threat to endemic wildlife.
2. The IUCN Red List includes the category "Critically Endangered." Describe what this category means and explain why a species might move from "Endangered" to "Critically Endangered" over time.
Wrap Up
In one sentence, what was the main idea of this lesson?