in which of the following the notochord is present in embryonic stage

Options

A. All chordates
B. Some chordates
C. Vertebrates
D. Non- chordates

Answer

To determine in which of the following the notochord is present in the embryonic stage, we can analyze the options given:

1. **All Chordates**
2. **Some Chordates**
3. **Vertebrates**
4. **Non-Chordates**

### Step-by-Step Solution:

**Step 1: Understand the Definition of Notochord**
- The notochord is a flexible rod-like structure that provides support and is a characteristic feature of chordates during their embryonic development.

**Step 2: Identify the Groups of Organisms**
- Chordates are a diverse group of animals that include all vertebrates (like mammals, birds, reptiles, amphibians, and fish) and some invertebrates (like tunicates and lancelets).

**Step 3: Analyze the Presence of Notochord**
- In all chordates, the notochord is present during the embryonic stage. It serves as a precursor to the vertebral column in vertebrates.
- In vertebrates specifically, the notochord is present during the embryonic stage but is later replaced by the bony vertebral column as the organism develops.
- Non-chordates, such as certain worms, do not possess a notochord at any stage of their development.

**Step 4: Evaluate the Options**
- **All Chordates**: Correct, as the notochord is present in all chordates during the embryonic stage.
- **Some Chordates**: Incorrect, as this implies that not all chordates have a notochord in the embryonic stage.
- **Vertebrates**: While vertebrates do have a notochord in the embryonic stage, this option is too specific since it excludes non-vertebrate chordates.
- **Non-Chordates**: Incorrect, as non-chordates do not have a notochord.

**Final Answer: All Chordates**