Choose the correct answer :
In a pond ecosystem , benthos means :

Options

A. Virus
B. Bacteria
C. Zooplanktons in water surface
D. Primary consumers in the depth of a pond

Answer

To solve the question regarding the meaning of "benthos" in a pond ecosystem, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Term "Benthos":**
- Benthos refers to the organisms that live on or in the bottom sediments of a body of water, such as a pond. This includes both plants and animals that are found in the benthic zone.

2. **Identifying the Layers of a Pond Ecosystem:**
- In a pond ecosystem, there are different layers, including the surface water, the water column, and the bottom sediments. The bottom layer, where benthos is found, is typically rich in nutrients and supports a variety of organisms.

3. **Characteristics of Benthos:**
- Benthos includes organisms such as worms, crustaceans, and various types of algae that are adapted to live in the sediment. These organisms play a crucial role in the ecosystem by breaking down organic matter and recycling nutrients.

4. **Conclusion:**
- Based on the information provided, benthos is defined as the last layer of the soil or sediment in a pond ecosystem, where various organisms reside.

5. **Choosing the Correct Answer:**
- Given the options provided in the question, the correct answer is the one that describes benthos as the organisms living in the bottom layer of the pond.

### Final Answer:
- The correct answer is **Option D**, which describes benthos as the organisms found in the last layer of the pond ecosystem.