Year 8 Science · Unit 1 · Lesson 15
Apply Worksheet
Learning Goals
Match each damaged part to its first knock-on effect
Write the matching letter in the middle column. Each letter is used once.
| Damaged part | Letter | First knock-on effect |
|---|---|---|
| Torn roots | A. Less digested food is absorbed into the blood. | |
| Blocked air passages | B. Wastes build up in the blood instead of being removed. | |
| Damaged lining of the small intestine | C. Less water and fewer minerals enter the plant. | |
| Weakened heart muscle | D. Less air reaches the gas-exchange surfaces in the lungs. | |
| Kidneys that stop working | E. Blood is pushed around the body more weakly, so tissues receive less. |
Odd one out
Circle the odd one out in each row and say why it does not belong.
| Items | Odd one out, and why |
|---|---|
| 1. less oxygen enters the blood · leaves droop · less water taken in · stem carries less water | |
| 2. heart · lungs · blood vessels · blood | |
| 3. torn roots · smoke in the lungs · a blocked blood vessel · a warm, sunny day |
Cause and effect: a leafless lemon tree
Caterpillars ate most of the leaves on a young lemon tree. Its roots were never touched, yet a few weeks later the roots had grown very little. Complete the chain. Each box is caused by the box before it.
Strong or weak explanation?
A strong explanation follows the cause all the way to the wider effect. Write “strong” or “weak” for each, and give a reason.
| Student explanation | Strong or weak? Why? |
|---|---|
| “Smoke reduced gas exchange in the firefighter’s lungs, so less oxygen entered her blood and reached her muscles, so she tired quickly.” | |
| “The fern’s leaves wilted because its roots were damaged.” | |
| “The roots turned brown, so the leaves decided to wilt as a warning.” | |
| “The kidneys stopped removing wastes, so wastes built up in the blood and were carried to cells all over the body, which then could not work properly.” |
Scenario: fish in a muddy creek
After heavy rain, fine mud washed into a creek. Fish exchange gases with the water through their gills, and fine mud particles can coat and clog the gills. A school water-watch group measured how muddy the water was at four sites (turbidity, in NTU: the higher the number, the muddier the water). They also watched five small fish at each site and counted how many times per minute each fish moved its gill covers, which pumps water over the gills.
| Site | Turbidity (NTU) | Gill-cover movements per minute (average of 5 fish) |
|---|---|---|
| A | 5 | 62 |
| B | 40 | 75 |
| C | 120 | 96 |
| D | 300 | 118 |
Source: sample data.
1. Describe the pattern in Table 1. Then calculate how many more gill-cover movements per minute the fish made at Site D than at Site A.
Answer movements per minute
2. The mud touches only the gills, yet a fish at Site D swims slowly and is easier for a bird to catch. Explain how a problem at the gills can affect the fish’s muscles. Name the two body systems involved.
3. (a) Suggest why fish in muddier water moved their gill covers faster. (b) The sites also differed in other ways. Name one other difference between the sites that could change how fast the fish move their gill covers, and say what this means for any conclusion drawn from Table 1.
4. A student says: “A problem in one organ only affects that organ’s own system.” Evaluate this claim. Use one plant example and one animal example from this sheet, and trace each one into at least one other part or system.
Match each damaged part to its first knock-on effect
Torn roots → C; Blocked air passages → D; Damaged lining of the small intestine → A; Weakened heart muscle → E; Kidneys that stop working → B.
Odd one out
1. less oxygen enters the blood (animal; the rest are the damaged-roots chain). 2. lungs (respiratory; the rest are circulatory). 3. a warm, sunny day (normal; the rest damage or block a component).
Cause and effect: a leafless lemon tree
Box 2: fewer leaves, so less photosynthesis and less sugar (food) made. Box 3: less sugar carried down the stem (phloem) to the roots, so root cells get less food for growth.
Strong or weak explanation?
Firefighter: strong (lungs → blood → muscles). Fern: weak (missing link: less water taken in and carried to the leaves). Brown roots: weak (leaves do not “decide”; no mechanism). Kidneys: strong (kidneys → blood → cells everywhere).
Go Deeper
1. The muddier the water, the more gill-cover movements per minute. 118 − 62 = 56 more movements per minute. [2 marks: 1 pattern, 1 calculation]
2. Clogged gills exchange less gas, so less oxygen passes from the water into the blood (respiratory system). The circulatory system then carries less oxygen to the muscle cells, so they release less energy and the fish swims slowly. [3 marks: 1 per step; both systems named]
3. (a) Less oxygen gets in with each movement, so the fish pumps more water over its gills to try to take in enough oxygen. (b) Any one: water temperature, oxygen dissolved in the water, fish size or species, water flow. So the data show a link, not proof that mud alone caused the change. [3 marks: 1 (a), 1 difference, 1 what it means]
Show What You Know
4. Marking guide (points expected): 1 position (the claim is wrong); 2 plant example traced beyond the damaged part (e.g. leaves eaten → less sugar → roots grow less); 2 animal example across two systems (e.g. clogged gills → less oxygen into blood → less carried to muscles; or kidneys → wastes in blood → cells affected); 1 principle: components interact, so a fault in one can spread. [6 marks]
Common error to watch for: in Q3 claiming the table “proves” mud caused the faster gill movements. The sites differ in more than mud, so the data only show a link.