Which of the following statements is true?

Options

A. All chordates are vertebrates
B. All vertebrates are chordates
C. Non-chordates have a vertbral column
D. Invertebrates possess a tubular nerve cord

Answer

To determine which of the statements is true regarding chordates and vertebrates, we can analyze each statement step by step:

### Step 1: Understand the Definitions
- **Chordates**: This is a phylum (Phylum Chordata) that includes animals with a notochord, a dorsal nerve cord, pharyngeal gill slits, and a post-anal tail at some stage of development.
- **Vertebrates**: This is a subphylum (Subphylum Vertebrata) within Chordata that includes animals with a backbone or vertebral column.

### Step 2: Analyze the Statements
1. **Statement 1**: "All chordates are vertebrates."
- This statement is **false** because not all chordates have a vertebral column. For example, tunicates (urochordates) and lancelets (cephalochordates) are chordates but are not vertebrates.

2. **Statement 2**: "All vertebrates are chordates."
- This statement is **true** because vertebrates are a subgroup of chordates. Therefore, all vertebrates possess the characteristics of chordates.

3. **Statement 3**: "Non-chordates have a vertebral column."
- This statement is **false** because non-chordates do not possess a vertebral column. The vertebral column is a characteristic feature of chordates.

4. **Statement 4**: "Invertebrates possess a tubular nerve cord."
- This statement is **false** because the tubular nerve cord is a defining feature of chordates, particularly vertebrates. Invertebrates do not have this structure.

### Conclusion
After analyzing each statement, the only true statement is:
- **"All vertebrates are chordates."**