Arthropods lack

Options

A. jointed appendages
B. cilia
C. respiratory organs
D. segmented body

Answer

The question "Arthropods lack" is not directly addressed in the video transcript provided, which focuses on silk fibers and their protein composition. However, I can provide a step-by-step solution based on general knowledge about arthropods.

### Step-by-Step Solution:

1. **Understanding Arthropods**: Arthropods are a diverse group of invertebrates that include insects, arachnids, myriapods, and crustaceans. They are characterized by their segmented bodies, jointed appendages, and exoskeleton made of chitin.

2. **Key Characteristics of Arthropods**:
- They possess an exoskeleton, which provides protection and support.
- They have jointed legs and segmented bodies.
- They undergo molting (ecdysis) to grow.

3. **Identifying What Arthropods Lack**:
- Unlike chordates, arthropods lack a backbone or vertebral column.
- They do not have a closed circulatory system; instead, they have an open circulatory system.
- They lack true bones, which are characteristic of vertebrates.

4. **Conclusion**: Based on the characteristics of arthropods, the statement can be concluded that "Arthropods lack a backbone (vertebral column)."

### Final Answer:
Arthropods lack a backbone (vertebral column).