Arthropod Classification worksheet with key features of Arachnids, Crustaceans, Insects, and Myriapods.

Let's complete the Arthropod Classification table based on the key features of each class. Arthropods are a large phylum that includes insects, spiders, crustaceans, and centipedes, among others. All share common traits: a tough exoskeleton made of chitin, segmented bodies, and jointed legs.

We'll fill in the table with accurate biological information for each class:

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✔ Completed Table

| Arthropod Class | Examples | Number of body segments? | Number of pairs of legs? | Presence of antennae? | Presence of gills? |
|---------------------|-------------|-------------------------------|-------------------------------|---------------------------|------------------------|
| Arachnids | Spiders, scorpions, ticks, mites | 2 (cephalothorax + abdomen) | 4 pairs (8 legs) | No | Usually no (respiratory organs: book lungs or tracheae) |
| Crustaceans | Crabs, lobsters, shrimp, crayfish | 3 (head, thorax, abdomen) | Varies (e.g., crabs have 5 pairs) | Yes (usually 2 pairs) | Yes (gills) |
| Insects | Bees, ants, butterflies, beetles | 3 (head, thorax, abdomen) | 3 pairs (6 legs) | Yes (1 pair) | No (respiration via tracheae) |
| Myriapods | Centipedes, millipedes | Many segments (each segment usually has one pair of legs) | Many pairs (centipedes: 15–177 pairs; millipedes: up to 300+ pairs) | Yes (1 pair) | No (respiration via tracheae or diffusion) |

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🔍 Explanation of Each Class

#### 1. Arachnids
- Examples: Spiders, scorpions, ticks, mites.
- Body Segments: Two main parts — cephalothorax (fused head and thorax) and abdomen.
- Legs: 4 pairs (8 legs total). They do not have wings.
- Antennae: Absent. Instead, they use pedipalps (appendages near mouth) for sensing.
- Gills: No. Most breathe through book lungs or tracheae.

#### 2. Crustaceans
- Examples: Crabs, lobsters, shrimp, barnacles.
- Body Segments: Three distinct regions — head, thorax, and abdomen.
- Legs: Typically 5 pairs of walking legs, but can vary (e.g., crabs have 5 pairs, some have modified claws).
- Antennae: Yes, usually two pairs (antennules and antennae), used for sensing and movement.
- Gills: Yes, they have gills for breathing underwater.

#### 3. Insects
- Examples: Bees, butterflies, ants, flies.
- Body Segments: Three parts — head, thorax, and abdomen.
- Legs: 3 pairs (6 legs total). Wings are present in most adults (but not all).
- Antennae: Yes, usually one pair (varies in shape and function).
- Gills: No. They breathe using tracheal systems (air tubes).

#### 4. Myriapods
- Examples: Centipedes, millipedes.
- Body Segments: Many segments, each bearing a pair of legs (except head).
- Legs: Many pairs — centipedes have 15–177 pairs, millipedes can have over 300.
- Antennae: Yes, one pair (long and sensory).
- Gills: No. They respire through tracheae or direct diffusion through the skin.

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🌟 Summary Notes:

- All arthropods have an exoskeleton, segmented bodies, and jointed appendages.
- The differences in number of body segments, legs, antennae, and respiratory structures help classify them into these four major classes.

This classification helps biologists identify and understand the evolutionary relationships and adaptations of different arthropods.