A biome is

Options

A. sum of ecosystems in a geographical area
B. sum of all ecosystems on the earth
C. biotic components in a population
D. biotic components in an ecosystem

Answer

### Step-by-Step Solution:

1. **Understanding the Definition of a Biome**:
- A biome is a large ecological area on the Earth's surface, characterized by specific climate conditions, vegetation, and wildlife. It encompasses various ecosystems that share similar characteristics.

2. **Identifying Key Components**:
- Biomes are defined by their climate, soil, vegetation, and wildlife. These components interact with each other to form a unique environment.

3. **Differentiating Between Options**:
- Let's analyze the given options:
- **Option 1**: Sum of ecosystems in a geographical area.
- **Option 2**: Sum of all ecosystems of the earth.
- **Option 3**: Biotic components in a population.
- **Option 4**: Biotic components in an ecosystem.
- From our understanding, a biome is specifically a collection of ecosystems within a defined geographical area, rather than the entire Earth or just biotic components.

4. **Selecting the Correct Answer**:
- Based on our analysis, the correct answer is **Option 1**: "Sum of ecosystems in a geographical area." This accurately reflects the definition of a biome.

### Final Answer:
A biome is the sum of ecosystems in a geographical area.