Question

6.2 invertebrates: arthropods
exercise 24
a. each sentence below is false. replace the underlined term
and rewrite the sentence to make it true.

1. an arthropod is an animal with an inner skeleton.

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1. arthropods have jointed heads.

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1. spiders are the largest group of arthropods.

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1. an insects body has two main parts.

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1. insects have feelers, which are called parasites.

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1. a crustaceans front pair of legs are called walking legs.

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b. complete the chart below with the correct numbers. the
first one is done for you.
critical thinking
on a separate sheet of paper, name three ways you can tell insects,
spiders, and crustaceans apart.

Explanation:

1. Arthropods have an exoskeleton (outer skeleton), not an inner skeleton.
2. Arthropods have jointed appendages (not just heads).
3. Insects are the largest group of arthropods, not spiders.
4. An insect's body has three main parts (head, thorax, abdomen), not two.
5. Insects' feelers are called antennae, not parasites.
6. A crustacean's front - pair of legs are called chelipeds (not walking legs).

For part B:

• Insects have 3 body segments.
• Spiders have 2 body segments.
• Crustaceans have 3 (or more variable, but often 3 main regions like cephalothorax and abdomen).
• Spiders have 4 pairs of legs.
• Crustaceans have 5 or more pairs of legs (depending on the species, but common crustaceans like crabs have 5 pairs of legs including chelipeds).

For critical thinking:

• Body segments: Insects (3), Spiders (2), Crustaceans (often 3 - cephalothorax and abdomen).
• Leg pairs: Insects (3 pairs), Spiders (4 pairs), Crustaceans (5 or more pairs).
• Antennae: Insects have 1 pair, Crustaceans have 2 pairs, Spiders have no antennae.

Answer:

1. An arthropod is an animal with an exoskeleton.
2. Arthropods have jointed appendages.
3. Insects are the largest group of arthropods.
4. An insect's body has three main parts.
5. Insects have feelers, which are called antennae.
6. A crustacean's front pair of legs are called chelipeds.

B:

• Insects: Number of body segments - 3; Number of pairs of legs - 3.
• Spiders: Number of body segments - 2; Number of pairs of legs - 4.
• Crustaceans: Number of body segments - 3 (e.g., cephalothorax and abdomen); Number of pairs of legs - 5 (e.g., crabs).

Critical thinking:

• By body segments: Insects (3), Spiders (2), Crustaceans (3 - cephalothorax and abdomen).
• By leg pairs: Insects (3), Spiders (4), Crustaceans (5 or more).
• By antennae: Insects (1 pair), Crustaceans (2 pairs), Spiders (none).