Primary 3 Science · Answers and explanations
Life Cycles of Plants
Use this page to check the worksheet together. Talk about why each answer is right. Total: 20 marks.
Section A · Multiple choice 8 marks
1. Look at Figure 1. How tall was Plant A on Day 4?1 mark
Figure 1: Height of three bean seedlings (cm)
| Plant | Day 2 | Day 4 | Day 6 | Day 8 |
|---|
| Plant A | 2 | 5 | 9 | 14 |
| Plant B | 1 | 3 | 6 | 8 |
| Plant C | 1 | 3 | 8 | 16 |
(A) 2 cm(B) 5 cm(C) 9 cm(D) 14 cm
Answer: (B) 5 cmRead across the row for Plant A to the Day 4 column.
2. Look at Figure 1. Which plant was the tallest on Day 8?1 mark
Figure 1: Height of three bean seedlings (cm)
| Plant | Day 2 | Day 4 | Day 6 | Day 8 |
|---|
| Plant A | 2 | 5 | 9 | 14 |
| Plant B | 1 | 3 | 6 | 8 |
| Plant C | 1 | 3 | 8 | 16 |
(A) Plant C(B) Plant A(C) Plant B(D) All the plants were the same height
Answer: (A) Plant COn Day 8 the heights were A 14 cm, B 8 cm and C 16 cm.
3. Look at Figure 1. By how many centimetres did Plant B grow from Day 2 to Day 6?1 mark
Figure 1: Height of three bean seedlings (cm)
| Plant | Day 2 | Day 4 | Day 6 | Day 8 |
|---|
| Plant A | 2 | 5 | 9 | 14 |
| Plant B | 1 | 3 | 6 | 8 |
| Plant C | 1 | 3 | 8 | 16 |
(A) 6 cm(B) 4 cm(C) 3 cm(D) 5 cm
Answer: (D) 5 cmOn Day 2 it was 1 cm and on Day 6 it was 6 cm, so 6-1=5.
4. The three cards in Figure 2 show stages of a plant. Which order shows the life cycle starting from the seed?1 mark
Figure 2: Three stages of a plant
(A) 2, 1, 3(B) 3, 2, 1(C) 2, 3, 1(D) 1, 3, 2
Answer: (C) 2, 3, 1Card 2 is the seed, card 3 is the young plant and card 1 is the adult plant with flowers and fruits.
5. Which part of an adult plant holds seeds?1 mark
(A) The leaf(B) The fruit(C) The stem(D) The soil
Answer: (B) The fruitAdult plants make flowers, and the flowers grow into fruits. Fruits contain seeds.
6. Look at Figure 3. Which young living thing does NOT look like its adult?1 mark
Figure 3: Some young living things and their adults
| Living thing | Young | Adult |
|---|
| Chick and hen | Fluffy feathers, two legs, a beak. Lives on land. | Feathers, two legs, a beak. Bigger. Lives on land. |
| Tadpole and frog | Has a tail and no legs at first. Lives in water. | Has four legs and no tail. Lives on land and in water. |
| Puppy and dog | Four legs, fur, a tail. Lives on land. | Four legs, fur, a tail. Bigger. Lives on land. |
(A) Tadpole(B) Chick(C) Puppy(D) All of them look like their adults
Answer: (A) TadpoleA tadpole has a tail and no legs at first, but an adult frog has four legs and no tail.
7. Why is it important for living things to reproduce?1 mark
(A) So the young never change(B) So the adult can stay small(C) So plants can stop making seeds(D) So living things of the same kind continue to exist
Answer: (D) So living things of the same kind continue to existReproduction makes new young, so that living things of the same kind keep existing.
8. Look at Figure 4. When did Plant D grow the most?1 mark
(A) Day 2 to Day 4(B) Day 6 to Day 8(C) Day 4 to Day 6(D) Day 8 to Day 10
Answer: (C) Day 4 to Day 6Work out the growth between each pair of days: Day 2 to Day 4: 2 cm, Day 4 to Day 6: 4 cm, Day 6 to Day 8: 1 cm, Day 8 to Day 10: 1 cm.
Section B · Show what you know 12 marks
9. Look at Figure 1. Describe how the height of Plant A changed from Day 2 to Day 8. Then predict its height on Day 10: will it be shorter than, the same as, or taller than 14 cm?2 marks
Figure 1: Height of three bean seedlings (cm)
| Plant | Day 2 | Day 4 | Day 6 | Day 8 |
|---|
| Plant A | 2 | 5 | 9 | 14 |
| Plant B | 1 | 3 | 6 | 8 |
| Plant C | 1 | 3 | 8 | 16 |
Answer: Plant A got taller each time it was measured (from 2 cm to 14 cm). On Day 10 it will be taller than 14 cm.1 mark for saying it grows taller over time (the numbers go up each time). 1 mark for predicting taller than 14 cm, using the pattern.
10. Look at Figure 2. Write the life-cycle stages in the correct order, beginning with the seed. Then name the part that the adult plant makes so that the cycle can start again.2 marks
Figure 2: Three stages of a plant
Answer: Seed, young plant, adult plant. The adult plant makes flowers and fruits that contain seeds.1 mark for the order seed, young plant, adult plant. 1 mark for flowers and fruits (the fruits hold the seeds), so the cycle repeats.
11. Look at Figure 3. Choose one of the animals. Say whether its young looks like its adult or looks different, and give one piece of evidence from the table.2 marks
Figure 3: Some young living things and their adults
| Living thing | Young | Adult |
|---|
| Chick and hen | Fluffy feathers, two legs, a beak. Lives on land. | Feathers, two legs, a beak. Bigger. Lives on land. |
| Tadpole and frog | Has a tail and no legs at first. Lives in water. | Has four legs and no tail. Lives on land and in water. |
| Puppy and dog | Four legs, fur, a tail. Lives on land. | Four legs, fur, a tail. Bigger. Lives on land. |
Answer: Example: A chick looks like a hen because both have feathers, two legs and a beak. (Or: a tadpole looks different from a frog because the tadpole has a tail and no legs, but the frog has four legs and no tail.)1 mark for the right statement (chick and puppy look like their adults; tadpole looks different). 1 mark for matching evidence from the table.
12. Sam planted a seed in a bag and measured it. Look at Figure 5. Sam says, "My plant is only a tiny seedling, so it is not growing." Do you agree? Use the numbers to explain.2 marks
Figure 5: Sam's seed diary (height in cm)
Answer: No. The seedling grew taller each time, from 1 cm to 3 cm to 7 cm, so it is growing.1 mark for disagreeing. 1 mark for using the numbers to show the height increases (the seed is growing into a young plant).
13. Mrs Lim ate a mango and planted its seed. Explain how this seed can lead to more mangoes in the future.2 marks
Answer: The seed grows into a young plant, which grows into an adult mango tree. The adult tree makes flowers and fruits with new seeds, so the cycle repeats.1 mark for the seed growing into a young plant and then an adult. 1 mark for the adult making flowers and fruits with seeds, so the cycle repeats.
14. Look at Figure 1. Which plant, A or C, grew more from Day 2 to Day 8? By how many centimetres more?2 marks
Figure 1: Height of three bean seedlings (cm)
| Plant | Day 2 | Day 4 | Day 6 | Day 8 |
|---|
| Plant A | 2 | 5 | 9 | 14 |
| Plant B | 1 | 3 | 6 | 8 |
| Plant C | 1 | 3 | 8 | 16 |
Answer: Plant C grew more, by 3 cm more.Plant A grew 14-2=12 cm. Plant C grew 16-1=15 cm. 1 mark for the plant, 1 mark for the difference of 3 cm.
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