Year 8 Science · Unit 1 · Lesson 23
Foundation Worksheet
Learning Goals
Fill the gap
Choose the correct word from the word bank. Two words will not be used.
A species that no longer exists anywhere on Earth is . A species that is still alive but at serious risk of disappearing is . The general word that covers every species at risk of extinction, including endangered ones, is . Australia’s long as an island continent meant its animals evolved without defences against many new dangers. Introduced such as foxes and cats hunt small native mammals, and land clearing for farms and cities causes loss.
1. Kangaroos, koalas and bilbies are marsupials. Explain why Australia’s long isolation let marsupials thrive, but also left them at risk once Europeans arrived.
Sort it
Write each threat in the correct box. Each box gets exactly two threats.
Habitat loss
Introduced species
Climate change
Put the steps to extinction in order
These events happened to a made-up small Australian marsupial. Number them from 1 (first) to 5 (last).
| Step (1–5) | Event |
|---|---|
| With so few animals left, the species is listed as endangered. | |
| Years later, the last animal dies and the species is extinct. | |
| The animals that remain are left in small, separate patches of bush. | |
| Settlers clear bushland for farms, so the marsupial loses most of its habitat. | |
| Foxes and cats hunt the animals in those small patches, and numbers keep falling. |
Read the data
Scenario: koalas in a growing shire
A council on the edge of a growing city counts the koalas in its bushland every five years. It also measures how much bushland is left.
| Year | Bushland left (hectares) | Koalas counted |
|---|---|---|
| 2000 | 1200 | 86 |
| 2005 | 1050 | 74 |
| 2010 | 820 | 51 |
| 2015 | 640 | 38 |
| 2020 | 500 | 27 |
Source: sample bushland survey figures.
2. Describe the pattern between bushland left and koalas counted, using numbers from Table 1. Explain it using what koalas need from their habitat.
3. A councillor says: “The koalas have just moved somewhere else. Clearing the bushland has nothing to do with it.” Give one piece of evidence from Table 1 against this claim. Then name two other threats from the lesson that could also explain part of the drop in koalas near a growing city.
4. Why are so many of Australia’s unique animals at risk? Connect the ideas of isolation, introduced species and habitat loss. Then use the numbat to describe one conservation approach that has helped.
Fill the gap
extinct; endangered; threatened; isolation; predators; habitat. Not used: zoo, drought.
1. Isolated for millions of years, marsupials had few placental mammals to compete with, so they thrived. But they evolved without defences against predators such as foxes and cats, so when these arrived with European settlers the marsupials had no time to adapt. [2 marks: 1 few competitors, 1 no defences against new predators]
Sort it
Habitat loss: bushland cleared for a housing estate; water taken from rivers, so wetlands shrink. Introduced species: foxes hunting bilbies; rabbits competing for food and burrows. Climate change: longer droughts; more frequent bushfires.
Put the steps to extinction in order
Reading down the table as printed: 4, 5, 2, 1, 3.
Read the data
2. As bushland decreased, the number of koalas decreased (86 down to 27). Koalas need bushland (gum trees) for food and shelter, so less bushland supports fewer koalas. [2 marks: 1 pattern, 1 reason linked to food or shelter]
3. Evidence: every time bushland fell, koala numbers fell too; the biggest loss of bushland (2005 to 2010, 230 hectares) came with the biggest drop in koalas (23). Other threats (any two): car strikes, dog attacks, disease such as chlamydia, bushfires. Accept a note that the table shows a link but cannot on its own prove the cause. [3 marks: 1 evidence, 1 per threat]
Show What You Know
4. Marking guide (points expected): 1 Australia was isolated for millions of years, so native species evolved without defences against predators such as foxes and cats; 1 introduced species named with its effect (foxes and cats hunt small mammals, or rabbits compete for food and burrows); 1 habitat loss from land clearing removes the food and shelter species need; 1 numbat: it survived only in small parts of Western Australia; 1 predator control and habitat protection let numbers grow, because threats were reduced where it lives. [5 marks]
Common error to watch for: using “endangered” and “extinct” as if they mean the same thing. Extinct is permanent; an endangered species is still alive, so there is still time to act.