Jawless fishes probably evolved

Options

A. before the seaweeds .
B. before the first photosynthetic organisms.
C. at the time of primitive atmosphere of Earth.
D. after the origin of turtles.

Answer

To solve the question regarding the evolution of jawless fishes, we will analyze the provided options in relation to the timeline of evolutionary events.

### Step-by-Step Solution:

1. **Identify the Group**: The question refers to jawless fishes, which are scientifically known as Agnatha.

2. **Determine the Evolution Timeline**: According to the information, jawless fishes (Agnatha) evolved approximately 500 million years ago.

3. **Examine the Options**:
- **Option 1**: Before the seaweeds.
- **Option 2**: Before the first photosynthetic organism.
- **Option 3**: Before the first land plants.

4. **Research the Evolution of Seaweeds**: Seaweeds are known to have evolved around 540 million years ago. Since jawless fishes evolved 500 million years ago, they indeed evolved after the emergence of seaweeds but before the first land plants.

5. **Research the Evolution of Photosynthetic Organisms**: The first photosynthetic organisms appeared approximately 3.2 to 3.5 billion years ago. This is significantly earlier than the evolution of jawless fishes.

6. **Analyze the Options**:
- **Option 1** (Before the seaweeds): This is incorrect because jawless fishes evolved after seaweeds.
- **Option 2** (Before the first photosynthetic organism): This is correct as jawless fishes evolved much later than the first photosynthetic organisms.
- **Option 3** (Before the first land plants): This is also correct since land plants evolved after jawless fishes.

7. **Conclusion**: The most accurate statement regarding the evolution of jawless fishes is that they evolved after the first photosynthetic organisms and before the first land plants. However, the question specifically asks about the timing relative to seaweeds, making the first option misleading.

### Final Answer: Jawless fishes probably evolved after the seaweeds.