Year 4 Science: Animals without a backbone
Part of the Year 4 Science grouping living things chapter. Chapter overview · whole chapter on one page
Animals without a backbone
Animals without a backbone are called invertebrates. There are many more invertebrates than vertebrates. The groups below are the ones often found in gardens and parks.
The table gives the main features of each group.
| Group | Main features |
|---|---|
| Snails and slugs | soft body; snails have a shell, and slugs have little or no visible shell |
| Worms | long soft body, no legs |
| Spiders | 8 legs and 2 body parts |
| Insects | 6 legs and 3 body parts |
Key ideas
- Invertebrates are animals without a backbone.
- A spider has 8 legs and 2 body parts.
- An insect has 6 legs and 3 body parts.
- Worms have a long soft body and no legs.
Method. Find the insect row in the table.
- Find the row. The row for insects says 6 legs and 3 body parts.6 legs
- Read the number. So an insect has 6 legs.6
- Write the answer. 6
Check. Count six legs on the insect picture. ✓
Method. Compare the body parts.
- Read the numbers. A spider has 2 body parts, and an insect has 3.2 and 3
- Compare them. An insect has 3 body parts, which is more than the spider, so the answer is insect.insect
- Write the answer. insect
Check. Three is more than two. ✓
Method. Check whether the worm has a backbone.
- Check the worm. A worm has a long soft body and no backbone.no backbone
- Decide. An animal without a backbone is not a vertebrate, so the answer is no.no
- Write the answer. no
Check. A worm is an invertebrate. ✓
Watch out
Watch out: a spider is not an insect. A spider has 8 legs and 2 body parts, while an insect has 6 legs and 3 body parts.
Try it at home or school (with a grown-up). Find a spider or an insect in a garden, with a grown-up, and look at it from a safe distance. Count its legs, and count its body parts. Do not touch the animal. Wash your hands afterwards.
Exam tip
Grown-up tip. Ask: “How many legs did you count? How many parts can you see on the body?” Let your child count carefully, and do not handle the animal.
Exercise 2C Animals without a backbone
Method. Read the table in section 2.3.
- Read the row for worms. Worms have a long soft body and no legs.no legs
- Decide. A worm has no backbone, so the answer is no.no
- Write the answer. no
Check. Worms are invertebrates. ✓
Method. Read the row for spiders.
- Read the row. The row for spiders says 8 legs.8 legs
- Write the number. A spider has 8 legs.8
- Write the answer. 8
Check. Spiders have eight legs. ✓
Method. Read the row for insects.
- Read the row. The row for insects says 6 legs.6 legs
- Write the number. An insect has 6 legs.6
- Write the answer. 6
Check. Insects have six legs. ✓
Method. Read the row for insects.
- Read the row. The row for insects says 3 body parts.3 body parts
- Write the number. An insect has 3 body parts.3
- Write the answer. 3
Check. The three parts are the head, the middle part and the back part. ✓
Method. Read the row for spiders.
- Read the row. The row for spiders says 2 body parts.2 body parts
- Write the number. A spider has 2 body parts.2
- Write the answer. 2
Check. A spider has fewer body parts than an insect. ✓
Method. Read the key idea in section 2.3.
- Read the key idea. Animals without a backbone are called invertebrates.invertebrates
- Write the answer. invertebrate
Check. Vertebrate means with a backbone, so invertebrate means without one. ✓
Method. Read the table in section 2.3.
- Read the numbers. The numbers 8 legs and 2 body parts are in the row for spiders.spiders
- Write the answer. spiders
Check. An insect has 6 legs and 3 body parts. ✓
Method. Compare the number of legs.
- Read the numbers. A spider has 8 legs, and an insect has 6 legs.8 and 6
- Compare them. 8 is more than 6, so the spider has more legs.spider
- Write the answer. spider
Check. Eight is more than six. ✓
Method. Check whether the snail has a backbone.
- Check the snail. A snail has a soft body and no backbone.no backbone
- Decide. So a snail is an invertebrate, not a vertebrate.no
- Write the answer. no
Check. Snails and slugs are invertebrates. ✓
Method. Compare the legs of each animal.
- Read the numbers. A spider has 8 legs, and an insect has 6 legs.8 and 6
- Choose the one with 6. So the animal with 6 legs is the insect.insect
- Write the answer. insect
Check. Count the legs on the picture to check. ✓
Method. Read the table in section 2.3.
- Read the row. The row for worms says a long soft body and no legs.no legs
- Write the answer. worms
Check. Earthworms are an example of worms. ✓
Method. Compare the two groups.
- Look at the insect. An insect has 6 legs and 3 body parts.6 legs and 3 body parts
- Look at the spider. A spider has 8 legs and 2 body parts.8 legs and 2 body parts
- Write the answer. Accept any sentence that says an insect has 6 legs and 3 body parts, while a spider has 8 legs and 2 body parts.
Check. Counting legs and body parts tells the two groups apart. ✓