PS RS P4L42 Revision 10 WS_2

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Topic: LIFE CYCLES / DIGESTIVE SYSTEM (LESSON 42)

Rocket Science | Primary 4

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Primary 4: Rocket Science

Lesson Outline

• Notes
• Activity 1: Fun facts
• Activity 2: MCQS
• Activity 3: Open-ended Questions
• Activity 4: Science in daily life

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Primary 4: Rocket Science

Revision – Life cycles

• A seed germinates when it gets sufficient air, water and warmth.
• After a few days, a young plant will grow from the seed. The young

plant is called a seedling.
• Initially, the seedling gets its food from the seed leaves. When the first

true leaves appear and turn green, the plant is able to carry out

photosynthesis (make its own food.)
• More leaves gradually grow to enable the plant to make more food.

Roots grow further into the soil to take in water and mineral salts for the

plant.
• After many weeks, the plant flowers and producesfruits.
• Fruits eventually ripen.
• Each fruit contains many seeds. When the seeds fall to the ground,

they are able to germinate if the conditions are right. A new life cycle

begins.

Number of Stages Stages Examples
in Life Cycle
- Cockroach
Adult Egg - Dragonfly
- Damselfly
Nymph - Grasshopper

Three - Birds, eg. chicken, crow

Adult Egg - Reptiles, eg. crocodile, lizard
- Fishes, eg. goldfish, clownfish

- Mammals that lay eggs, eg.

AR Model – Anteater platypus and spiny anteater

Young - Amphibians

Adult - Butterfly
- Mosquito
Four Egg - Housefly
- Moth
- Mealworm beetle

Pupa Larva AR Model – Moth

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Primary 4: Rocket Science

Revision – Digestive system
Use the given words to complete the following concept map.

stomach gullet small intestine large intestine

simpler substances saliva blood mouth

Digestive system
function

To break down food into
1.

so that the food can be absorbed by the body

Food enters

2. where
(contains digestive juices) moistens the
food and partially digests it
Tongue pushes food into

3. AR Model – Digestive System

Food then enters Absorbed into the
6.
4. where food is broken
Carried to
down into simpler substances. Different parts of the
Food stays here for 4 – 6 hours. body

Food then enters Digested
food
5. where food is
broken down into simpler
substances.

Undigested food enters

7. where
water is absorbed from it.

Undigested food leaves the
body as faeces through the
Anus

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Primary 4: Rocket Science

Activity 1 – Fun facts: Shark reproduction

https://www.youtube.com/watch?v=BWI60arRyG4
Discussion Questions:
1. Sharks produce far fewer offspring as compared to most fishes.
How is this an advantage?

2. What is the relationship between the mass of the yolk sac and the
mass of the embryo as it develops in the egg?

3. How can overfishing make sharks especially vulnerable? (3.00min)

4. Some species of sharks give birth to live young. Give some examples
of small aquarium fish that give birth to live young.

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Primary 4: Rocket Science

Activity 2 – MCQs

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Primary 4: Rocket Science

1. Which one of the following is not an insect?
(1) (2)

(3) (4)

()

2. Study the table below carefully.

Animal Lay eggs Characteristics Has moist skin
✓
F ✓ Has feathers x
G ✓ ✓

x

Which group of animals can F and G be?

F G
(1) Insects Amphibians
(2) Birds Amphibians
(3) Birds
(4) Amphibian Insects
Insects

()

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3. Study the classification table below. Primary 4: Rocket Science
Group A
Group B

dolphin dog grasshopper bee

whale bat

Which animal is grouped wrongly? ()

(1) bat
(2) whale
(3) dolphin
(4) grasshopper

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Primary 4: Rocket Science

4. Study the following classification table.
Animals

Young lives on Young lives in
land water

3-stage 4-stage 3-stage 4-stage
life cycle life cycle life cycle life cycle

Cockroach A BC

What could A, B and C be? C
AB mosquito

(1) beetle grasshopper beetle
mosquito
(2) butterfly grasshopper butterfly

(3) butterfly frog

(4) mosquito frog

( )

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Primary 4: Rocket Science

5. Four students studied the life cycles of the mosquito and the housefly.

They made comparisons of the life cycles of the two animals shown below.
A tick (✓) indicates that the statement is correct and a cross (X) indicates

that the statement is incorrect.

Child Statement Mosquito Housefly

John Lays eggs in water X ✓
Mary X X
Tony Young resembles the ✓ ✓
Susan adult ✓ X

Has four stages in its life
cycle

Is considered a pest in the
adult stage

Who made the correct comparisons?

(1) John and Mary only
(2) Tony and Mary only
(3) John and Susan only
(4) Tony and Susan only

()

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Primary 4: Rocket Science

6. The graph below shows the number of days that Insects A and B spend at
each stage of their life cycles.

At which stage of their life cycles would Insects A and B be on the 9th day
after the eggs hatch?

Insect A Insect B

(1) larva pupa

(2) larva adult

(3) adult pupa

(4) pupa larva

()

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Primary 4: Rocket Science

7. Study the flowchart below carefully.

Which of the following is correct?

PQRS

(1) Small intestine Stomach Gullet Large intestine

(2) Stomach Small intestine Gullet Large intestine

(3) Small intestine Stomach Large intestine Gullet

(4) Stomach Large intestine Small intestine Gullet

()

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Primary 4: Rocket Science

8. Which of the following shows the correct order when food moves through
some parts of the digestive system?

(1)

(2) stomach small intestine
large intestine

(3)

(4) large intestine stomach
small intestine
(
)

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Primary 4: Rocket Science

9. Study the diagram below.

W
X
Z

Y

Digestion does not take place in .

(1) Y only ()
(2) Z only
(3) X and Z only
(4) W and Z only

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Primary 4: Rocket Science

10. Lina had just finished eating an apple. What happens to the apple during
digestion?

Arrange the stages of digestion of the apple in the correct order.

A. Excess water is absorbed.
B. It is chewed into smaller pieces.
C. Undigested food is passed out of the body.
D. Nutrients is absorbed through the walls of the intestine into the blood.

(1) A B C D
(2) B A D C
(3) B D A C
(4) D A C B

()

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Primary 4: Rocket Science

11. The graph below shows the amount of digested food found in four different
organs of a human digestive system before absorption into the blood
stream.
Amount of digested food

AB C D Organs in digestive system

Which organ is the small intestine? ()

(1) Organ A
(2) Organ B
(3) Organ C
(4) Organ D

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Primary 4: Rocket Science

12. Kayla wanted to conduct an experiment to see if the size of food pieces
would affect the time taken to digest the food.
She prepared pieces of bread, cut into different sizes, and measured the
amount of time taken for the food to be completely digested. The diagram
below shows examples of the pieces of bread she had prepared.

Which graph most accurately shows the relationship between the size of
the bread pieces and the time taken for the food to be digested?

(1) Amount (2)
of time
taken for Amount
of time
food to be taken for
digested food to be
digested

(3) Size of bread Size of bread
pieces (4) pieces
Amount
of time Amount
taken for of time
food to be taken for
digested
food to be
digested

Size of bread Size of bread
pieces pieces

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Activity 3 – Open-ended Questions
1. Study the life cycles of two animals, X and Y, below carefully.

(a) By comparing the life cycles, state 1 similarity and 1 difference [2]
between animal X and animal Y.

(i) Similarity:

(ii) Difference:

(b) Eva keeps animal X as a pet after the egg has hatched. She went on a
holiday and forgot to feed animal X for 9 days. However, animal X did
not die.

(i) At which stage of the life cycle could animal X be? [1]

(ii) Explain your answer in (i). [1]

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2. John observed that insects A and B have been feeding on the leaves of the
plant. To know more about insects A and B, John started to study the life
cycles of both insects.

Insect AB

Mass of leaves eaten by 100 100
the larvae per day (grams)

Only the larvae of insects A and B feed on the leaves of the plant. The table
below shows the amount of leaves which the larvae of insects A and B feed
on per day.

Based on the data above, John concluded that insect A is more harmful
towards the plant than insect B.

Do you agree with John? Explain your answer. [2]

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Primary 4: Rocket Science

3. Joanne wanted to find out which type of food digests the fastest. She placed
the food, A, B and C in three separate identical cups of digestive juice for 5
hours.

digestive cup
juice

food A food B food C

The graph below shows the results of the amount of food left after 5 hours.

Type of
food

A

B

C

Amount of food left

(a) From the results above, which type of food, A, B or C digests the

fastest? [1]

(b) Explain your answer in (a). [1]

(c) Besides the cups, name two other variables that should be kept the

same for this experiment. [2]

(i)
(ii)

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Primary 4: Rocket Science

4. Daniel ate a burger in the afternoon. The graph below shows the amount of
digested food in the digestive system as it passes through each part of the
system.

Mass of

digested
food (g) 12

10

8

6

4

2

0

Mouth Gullet F Small Large

Intestine Intestine

(a) What does part F represent? [1]

(b) Explain why the value in the graph for “Large Intestine” is 0g. [1]

(c) Some types of bacteria cause food poisoning. When food poisoning
happens, a person cannot absorb digested food properly into the
body.

Suggest a value for the mass of digested food in the large intestine,

when this person eats a burger. Give a reason for your answer. [2]

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Primary 4: Rocket Science
Activity 4 – Science in daily life: Head lice feeding

https://www.youtube.com/watch?v=EdX2PFkKBtU&t=105s
Discussion Questions:
1. Are head lice insects? What characteristics do we look out for to confirm

this?
2. What are parasites? Name 2 other parasites that affect humans.
3. There are visible movements called peristalsis that is observed as the head

louse was feeding on the man. How does this movement help all digestive
systems?
4. Female mosquitos suck blood while male mosquitos suck plant sap.
How does this help the mosquito reproduce?

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