Year 8 Science · Unit 1 · Lesson 14
Challenge Worksheet
Learning Goals
Find the errors
This paragraph has exactly three errors. Underline each one and correct it below.
A student’s comparison
A fig tree and a flying-fox (fruit bat) are both living systems, because each has organised parts that work together. However, only the flying-fox needs to move materials around; the fig tree has no transport at all because it has no heart. Both take in materials from their surroundings: the fig tree takes in water and minerals through its leaves, and the flying-fox eats figs. Because the two do similar jobs, they must use the same structures to do them.
1. Write the three corrections.
Fact file: moving materials in a tall tree and in a person
A tree and a person both need to move materials around. The tree has no pump: water rises through tubes in its trunk. A person’s heart pumps blood through blood vessels.
| Living thing | What is moved | What moves it | Typical figure |
|---|---|---|---|
| Tree, 30 m tall | water from roots to top leaves | no pump; tubes in the trunk | rises about 2 m per hour on a sunny day |
| Resting adult | blood around the whole body | the heart, through blood vessels | one full trip around the body takes about 1 minute |
Source: rounded values for teaching; real speeds vary with the tree, the weather and the person.
2. (a) How many hours does it take water to travel from the roots to the top leaves of the tree? (b) In that same time, how many full trips around the body could the resting adult’s blood make?
(a) hours (b) trips
3. A student says, “The tree’s transport is so slow that it does not really count as a transport system.” Use Table 1 and your answers to Q2 to evaluate this.
Rank the comparisons
Three answers to “Compare how a wattle and a wombat take in water.”
X: “They are completely different. The wattle is a plant and the wombat is an animal.”
Y: “Both need water. The wattle’s roots take in water from the soil, while the wombat drinks and also gets water from the grass it eats. Same need, different structures.”
Z: “They are the same, because the wattle’s roots are its mouth.”
4. Decide which of X, Y and Z is the best comparison and which is the poorest, with a reason for each. Then fix answer Z so that it is correct.
5. A student claims: “Plants and animals are basically the same as living systems. They both have interacting parts, so the details are just minor variations.” Evaluate this claim.
Find the errors
1. (i) The fig tree does move materials: water and minerals travel up through tubes in its trunk (stem), with no heart needed. (ii) The fig tree takes in water and minerals through its roots, not its leaves. (iii) Similar jobs can be done by different structures (for example, trunk tubes in the tree, and the heart and blood vessels in the flying-fox). [3 marks: 1 per correction]
Your Turn
2. (a) 30 m ÷ 2 m per hour = 15 hours. (b) 15 hours × 60 = 900 minutes, at 1 trip per minute = about 900 trips. [3 marks: 1 (a); 1 converting hours to minutes; 1 (b)]
3. Partly true: it is far slower (about 900 blood trips in the time water climbs the tree once). But it is still a transport system: tubes in the trunk move water and minerals from the roots to every leaf, even 30 m up, which keeps the tree alive. The job is the same; the structure and speed are different. [3 marks: 1 slower, with data; 1 still moves materials to where they are needed; 1 judgement: a different structure doing the same job]
Rank the comparisons
4. Strongest Y: it names the shared need and the different structure in each. Middle X: true that they differ, but it names no structures or jobs and misses what they share. Weakest Z: it wrongly says the structures are the same; roots are not a mouth. (Accept X and Z swapped if well argued.) Rewrite of Z, for example: “Both need water, but they use different structures: the wattle’s roots take in water from the soil, and the wombat drinks through its mouth.” [4 marks: 1 ranking; 1 reasons; 2 correct rewrite naming both structures]
Show What You Know
5. Marking guide (points expected): 1 correct part: both are living systems with interacting parts and both need materials from the environment; 2 two life jobs with both structures named (for example, moving materials: stem tubes, no pump, against heart, blood vessels and blood; getting food: leaves make food using light, against eating and digesting; taking in water: roots against drinking); 1 the role of each named structure is stated (structure → role → function); 1 why these are not minor: the body plan and the way each job is done are different, so they cannot be swapped part for part; 1 judgement: similar jobs, different structures, so they are not “basically the same”. [6 marks]
Common error to watch for: treating “not the same” as “nothing in common”. The strongest answers keep the shared jobs and the different structures side by side.