Year 7 Science · Unit 1 · Lesson 11
Foundation Worksheet
Learning Goals
Fill the gap: the Unit 1 map
Choose the correct word from the word bank. Each word is used once. Two words are not needed: cross them out.
Unit 1 asked one big question: what are living things, and how are they built and sorted? First, the seven characteristics summed up by tell us whether something is alive. Only living things are sorted into groups by their shared features, and this sorting is called . The biggest groups we used are domains and , and animals are split into vertebrates and . The idea called says that every living thing is made of one or more cells, and that all cells come from existing cells. Plant cells have three parts that animal cells lack: a cell wall, a large vacuole and . In large organisms, cells become for one job and group into tissues, then , then organ systems.
1. Every formal investigation follows the steps Q, H, M, R, D, C. Write the name of each step, in order.
Scenario: hatching brine shrimp
Brine shrimp are tiny animals that live in salty lakes. Priya asks: Does the amount of salt in the water affect how many brine shrimp eggs hatch? She fills 15 identical cups with 200 mL of water at 25 °C. Each group of three cups gets a different amount of salt: 0, 10, 30, 50 or 70 grams per litre (g/L). She adds 50 eggs to every cup and keeps all the cups on the same bench under the same lamp. After 48 hours she counts how many eggs have hatched in each cup.
Sort the variables
Write each item from Priya’s investigation in the correct box. The boxes do not hold the same number of items.
Independent (changed)
Dependent (measured)
Controlled (kept the same)
2. Write a hypothesis for Priya’s investigation by completing the sentence. Your “because” must give a reason.
If the amount of salt in the water …
then the number of eggs that hatch will …
because …
Read the data
Priya’s results
Table 1 shows how many of the 50 eggs hatched in each cup after 48 hours.
| Salt (g/L) | Cup 1 | Cup 2 | Cup 3 | Average |
|---|---|---|---|---|
| 0 | 2 | 0 | 1 | 1 |
| 10 | 18 | 21 | 18 | 19 |
| 30 | 39 | 41 | 40 | |
| 50 | 33 | 12 | 36 | 27 |
| 70 | 20 | 23 | 20 | 21 |
Source: made-up sample class results for this worksheet.
3. Calculate the average number of eggs hatched at 30 g/L. Show your working, then write the answer in Table 1.
Average eggs
4. Describe the pattern in the averages as the amount of salt goes up from 0 to 70 g/L. Quote two numbers from Table 1.
5. One cup at 50 g/L does not fit the other two. Which cup is it? Explain why it was useful that Priya set up three cups at each amount of salt, not one.
6. Jack repeats Priya’s investigation, but he uses only one cup at each amount of salt. There is no room on the bench, so he puts the two saltiest cups next to a warm heater. He says: “My results prove that salty water stops eggs hatching.” Explain two problems with Jack’s investigation and how he should fix each one.
Fill the gap: the Unit 1 map
MRS GREN; classification; kingdoms; invertebrates; cell theory; chloroplasts; specialised; organs. Not used: mitochondria (both cell types have them), photosynthesis.
Question 1
Question, Hypothesis, Method, Results, Discussion, Conclusion: all six in order (2), four or five (1). [2 marks]
Sort the variables
Independent: amount of salt (g/L). Dependent: number of eggs that hatch. Controlled: water temperature; volume of water; number of eggs added; time before counting; light from the same lamp.
Question 2
E.g. If the amount of salt increases, then more eggs will hatch, because brine shrimp live in salty lakes. Both variables with a direction (1); a reason (1); “fewer” is fine with a reason. [2 marks]
Question 3
(39 + 41 + 40) ÷ 3 (1) = 40 eggs (1). [2 marks]
Question 4
Rises from 1 at 0 g/L to a peak of 40 at 30 g/L (1), then falls to 21 at 70 g/L (1). [2 marks]
Question 5
Cup 2 (12 eggs) (1). Three cups let her spot an unusual result so one odd cup cannot decide it; with one cup she could not tell a fluke from a real effect (1). [2 marks]
Question 6
Marking guide: temperature changed as well as salt, a second independent variable (1), so he cannot tell which caused any change (1); fix: keep all cups at the same temperature (1). One cup per salt amount means one odd cup could decide the result (1); fix: three or more replicate cups, averaged (1). [5 marks]
Model answer: The saltiest cups were also the warmest, so Jack cannot tell if salt or heat caused a change; all cups need the same temperature. With one cup per level, one odd cup could mislead him, so he needs three or more cups per level, averaged.
Common error: calling the heater a “controlled variable”; it was different for some cups, so it is uncontrolled.