Science: Invertebrates: Insects, Arachnids, and Mollusks
Classifying animals by body structures and traits
Science: Invertebrates: Insects, Arachnids, and Mollusks
Classifying animals by body structures and traits
Biology - Grade 4-5
- 1
An animal has six legs, three body parts, and two antennae. Is it an insect, an arachnid, or a mollusk? Explain how you know.
Think about the body plan of a butterfly or an ant.
It is an insect. Insects have six legs, three main body parts, and one pair of antennae. - 2
A spider has eight legs and no antennae. Is a spider an insect, an arachnid, or a mollusk? Explain your answer.
A spider is an arachnid. Arachnids have eight legs and do not have antennae. - 3
A snail has a soft body and often carries a shell. Is it an insect, an arachnid, or a mollusk? Explain how you know.
Think about animals with soft bodies that may live on land or in water.
A snail is a mollusk. Mollusks have soft bodies, and many mollusks have shells for protection. - 4
Name one way insects are different from arachnids.
One way insects are different from arachnids is that insects have six legs, while arachnids have eight legs. - 5
A crab is not one of the three groups in this worksheet. Explain why a crab is not an insect, arachnid, or mollusk.
Not all animals without backbones belong to these three groups.
A crab is not an insect, arachnid, or mollusk because it is a crustacean. Crabs have a different body structure and belong to a different invertebrate group. - 6
A bee, an ant, and a butterfly all belong to the same group. What group is it, and what trait do they share?
They all belong to the insect group. They share traits such as having six legs and three main body parts. - 7
Why is an octopus classified as a mollusk even though it does not have a shell?
Some members of a group share important traits even if they do not all look the same.
An octopus is classified as a mollusk because it has a soft body and belongs to the mollusk group. Not all mollusks have outside shells. - 8
Which group usually has antennae: insects, arachnids, or mollusks? Write a sentence to explain.
Insects usually have antennae. Arachnids do not have antennae, and mollusks have different body structures. - 9
A scorpion has eight legs and belongs to the same group as spiders. What group is it in, and what feature helps you classify it?
Count the legs and compare them to a spider.
A scorpion is an arachnid. Its eight legs help classify it in the arachnid group. - 10
Explain why a clam is a mollusk.
A clam is a mollusk because it has a soft body and a shell that protects it. These are common traits of many mollusks. - 11
A student says a centipede is an insect because it has many legs. Is the student correct? Explain your answer.
Having legs does not automatically make an animal an insect.
The student is not correct. A centipede is not an insect because insects have exactly six legs, while centipedes have many more than six legs. - 12
Write one sentence that tells how insects, arachnids, and mollusks are alike.
Insects, arachnids, and mollusks are alike because they are all invertebrates, which means they do not have backbones.