Year 7 Science · Unit 1 · Lesson 12
Challenge Worksheet
Learning Goals
1. List the six sections of a scientific report in order. Which section must contain no explaining at all?
Which explanation works?
Four students explain the bilby’s claws
A. “Bilbies are better animals than kangaroos because they can dig.”
B. “Long, strong claws let the bilby dig a deep burrow, where it shelters by day in soil much cooler than the scorching desert surface.”
C. “The bilby grew long claws because it needed to escape the heat.”
D. “Long claws are a better design than short claws.”
2. Which statement is a scientific explanation of an adaptation? Name the mistake made in each of the other three.
Mark the report
Below is a Year 7 student’s Discussion paragraph from a habitat survey. You are marking it, not rewriting it yet.
Student’s Discussion
“The leaves on the ridge were small and the leaves in the gully were big. The ridge plants grew small leaves so they could survive the dry weather. This proves that ridge plants are better adapted. There could have been some errors in our experiment.”
3. A Discussion should open by stating the result. What does the first sentence need so that it states the result properly?
4. The second sentence describes the plants as choosing a feature. Rewrite it so that it describes what the feature does in that habitat instead.
5. Explain what is wrong with the third sentence, and what is wrong with the last one.
Compare two surveys
Scenario: two surveys of one creek bank
Two students survey the same creek bank on the same morning. Student A walks along the bank and photographs anything that looks interesting. Student B places a 50 cm quadrat every 5 m along a 40 m tape (9 quadrats, from 0 m to 40 m) and records everything inside each one.
Student A’s photos: an eastern water dragon on a rock, a flowering bottlebrush, a large orb-weaver spider web, a kookaburra.
| Organism | Quadrats where found |
|---|---|
| Grass | 8 |
| Ants | 6 |
| Moss | 5 |
| Leaf-litter beetles | 4 |
| Tree seedlings | 2 |
| Eastern water dragon | 0 |
Source: made-up sample results for this worksheet.
6. Moss turned up in 5 of Student B’s 9 quadrats. What percentage of the quadrats is that? Give it to the nearest 1%.
Answer %
7. Student A concludes: “The creek bank is mostly large animals and flowering plants.” Use both sets of results to explain why only Student B’s survey can support a conclusion about what lives on the creek bank.
8. Student B’s survey still has limits. Name one specific limitation Student B should declare, and say how it affects the conclusion.
9. Rewrite the student’s Discussion paragraph from “Mark the report” so that it uses all five steps. Invent sensible measurements where the student gave none.
Question 1
Aim, Prediction, Method, Results, Discussion, Conclusion (1). Results: only measurements and observations, no explaining (1). [2 marks]
Which explanation works?
No separate marks: this stimulus is marked in Question 2.
Question 2
B is the scientific explanation: it names the feature, the condition and how they connect (1). A ranks two organisms as “better”, which has no meaning without a habitat (1). C describes the bilby getting a feature because it needed it; individuals do not grow adaptations on purpose; bilbies with those claws survived and reproduced more (1). D calls one feature better without saying in what conditions (1). [4 marks]
Mark the report
Marked in Questions 3 to 5.
Question 3
Measurements, e.g. average leaf lengths at each site (22 mm vs 41 mm), instead of “small” and “big” (1). [1 mark]
Question 4
E.g. “On the dry, windy ridge, small leaves lose less water, so plants with smaller leaves survive and reproduce better there.” Describes what the feature does (1) and names the ridge conditions (1). [2 marks]
Question 5
Third sentence: “better adapted” ranks the plants; each is suited to its own site (1), and one survey cannot “prove” anything (1). Last sentence: too vague; it must name a specific weakness, such as the number of leaves measured or a second difference between the sites (1). [3 marks]
Compare two surveys
Marked in Questions 6 to 8.
Question 6
5 ÷ 9 × 100 (1) = 55.6, so 56% (1). [2 marks]
Question 7
Student A chose what to record while recording it, so the photos are biased to large, colourful or unusual organisms (1). Student B’s data show the bank is mostly small, drab organisms (grass in 8 of 9 quadrats, ants 6, moss 5), none of which A recorded (1). B fixed the sampling rule before starting, so what was recorded did not depend on what caught the eye (1), and another student could repeat it and compare results (1). [4 marks]
Question 8
Any specific limitation (1) with its effect (1), e.g. one tape on one morning samples a narrow strip at one time, so it cannot show other parts of the bank or seasonal change; mobile animals (such as the water dragon) move out of a quadrat, so they are under-counted. [2 marks]
Question 9
Marking guide: 1 result in numbers; 1 condition that differs (sun and wind on the ridge, shade and shelter in the gully); 1 mechanism (smaller, thicker leaf, less surface area per gram, less water lost); 1 direction (condition first, feature as the response); 1 what would have made it wrong; 1 a specific limitation. [6 marks]
Model answer: Wattle leaves on the ridge averaged 22 mm long, about half the 41 mm of leaves on the same species in the gully, and were thicker. The ridge is in full sun and wind all day while the gully is shaded and sheltered, so ridge plants lose water faster. A smaller, thicker leaf has less surface area for each gram of leaf, so less water escapes; that is an advantage on the ridge and unnecessary in the gully. If ridge leaves had been the same size or larger, this explanation would not hold. Only six leaves were measured at each site, and the sites also differ in soil depth, so shade and wind may not be the only cause.
Common error: writing the direction backwards, e.g. “it was dry because the leaves were small”, or ending with “there could have been errors”.