Year 8 Science · Unit 1 · Lesson 22
Foundation Worksheet
Learning Goals
Fill the gap
Choose the correct word from the word bank. Two words will not be used.
All the organisms of one species living in one area make up a . It grows when there are more than . Animals moving into the area from somewhere else is called , and animals leaving the area is called .
True or false? Fix the false ones
Circle T or F. If a statement is false, correct it on the line.
1. Introduced species always die out quickly in a new country.
Correct it:
2. Cane toads were brought to Australia to eat rabbits.
Correct it:
3. Kangaroo numbers can rise when there is plenty of grass.
Correct it:
4. Cane toads are harmless to native animals because they mainly eat insects.
Correct it:
5. Foxes and cats have caused the decline of many small native mammals.
Correct it:
6. By stripping away plants, rabbits caused soil erosion in Australia.
Correct it:
Sort it: bigger or smaller?
Write each change in the box for what it does to a population.
Makes the population bigger
Makes the population smaller
Put the rabbit story in order
Number the events from 1 (first) to 5 (last).
| Event (1–5) | What happened |
|---|---|
| With a mild climate, plenty of food and almost no predators, far more rabbits were born than died. | |
| Bare ground was left behind, and the soil washed and blew away. | |
| Rabbit numbers exploded and spread across the continent. | |
| Rabbits were brought to Australia in 1859. | |
| Huge numbers of rabbits ate native plants and competed with native herbivores such as bilbies. |
Read the data
Scenario: a rock pool survey
A class counted the periwinkle snails in one rock pool at low tide every week for 6 weeks. They also wrote down anything unusual that happened that week.
| Week | Snails counted | Notes |
|---|---|---|
| 1 | 42 | calm weather |
| 2 | 45 | calm weather |
| 3 | 29 | big storm and heavy rain |
| 4 | 33 | calm weather |
| 5 | 36 | calm weather |
| 6 | 21 | many predatory fish seen in the pool |
Source: sample class results.
1. In which week was the count highest? How many fewer snails were counted in week 6 than in week 5?
2. There are two sudden drops in Table 1. For each one, use the notes to suggest a cause.
3. Foxes now live across almost all of mainland Australia. A local council plans to get rid of every fox in its district within one year. Explain why foxes did so well after arriving here, and why the council’s plan is unlikely to work.
Fill the gap
population; births; deaths; immigration; emigration. Not used: decomposers, extinction.
True or false
1. False: many introduced species thrive, because they have plenty of food and few natural predators or diseases. 2. False: cane toads were brought in (1935) to control beetles in sugar cane fields. 3. True. 4. False: their skin is toxic, so goannas, quolls and snakes that try to eat them are poisoned; they also compete with native species for food. 5. True. 6. True.
Sort it: bigger or smaller?
Bigger: more babies are born; animals arrive from a nearby area; plenty of food after good rain. Smaller: a drought kills the grass; a disease spreads; a new predator arrives.
Put the rabbit story in order
Reading down the table as printed: 2, 5, 3, 1, 4.
Read the data
1. Week 2 (45 snails). 36 − 21 = 15 fewer. [2 marks]
2. Week 3: the storm and heavy rain probably killed snails or washed them out of the pool. Week 6: the predatory fish probably ate many snails. [2 marks: 1 each]
Show What You Know
3. Marking guide: 1 in Australia foxes face few diseases and limited competition, and they are skilled hunters with plenty of prey; 1 so births stayed higher than deaths and the population spread across the continent; 1 hard to remove because they are widespread and breed quickly, so every surviving fox can rebuild numbers; 1 foxes from neighbouring districts would move back in (immigration), so control needs long-term effort over large areas. Model answer: Foxes had plenty of prey and few diseases or competitors here, so births outnumbered deaths and they spread almost everywhere. The council cannot find every fox in a year, and any that survive keep breeding. Foxes from nearby districts would also move in, so the population would soon recover unless control continues for many years. [4 marks]
Common error to watch for: thinking a pest can just be “rounded up”. Once an introduced species is widespread and breeding, removing every animal is extremely difficult.