Which of the following is not a semelparous organism?

Options

A. Pacific salmon
B. Lamprey
C. Spider
D. Cow

Answer

To determine which of the following organisms is not a semelparous organism, we first need to understand the definition of semelparity. Semelparous organisms are those that reproduce only once in their lifetime and then die.

### Step-by-Step Solution:

1. **Define Semelparity**: Semelparous organisms reproduce only once during their entire life cycle. After this single reproductive event, they typically die.

2. **Identify Examples of Semelparous Organisms**:
- **Pacific Salmon**: These fish migrate to spawn, reproduce once, and then die. They are a classic example of semelparity.
- **Lamprey**: Similar to salmon, lampreys also reproduce once and die after laying their eggs. They are semelparous.
- **Spiders**: Many spider species lay eggs once and die shortly after. They are also considered semelparous.

3. **Identify the Non-Semelparous Organism**:
- **Cow**: Cows are mammals that can reproduce multiple times throughout their lives. They do not fit the definition of semelparity because they can give birth to several calves over their lifetime.

4. **Conclusion**: Among the options provided, the cow is the organism that is not semelparous.

### Final Answer:
The organism that is not a semelparous organism is the **cow**.