To determine which ecological unit or relationship is least related to abiotic factors, we can analyze the options provided:
1. **Community**: A community consists of different populations of species that live together in a particular area. Communities are influenced by abiotic factors such as climate, soil, and water availability, as these factors affect the survival and distribution of the species within the community. Therefore, communities are significantly related to abiotic factors.
2. **Symbiosis**: Symbiosis refers to the close and often long-term interaction between two different biological species. This relationship can be mutualistic, commensalistic, or parasitic. In mutualism, for example, both species benefit from the relationship, and their interaction may reduce their dependence on abiotic factors since they can rely on each other for resources. Thus, symbiosis is less dependent on abiotic factors compared to other ecological units.
3. **Population**: A population is a group of individuals of the same species living in a specific area. Populations are also influenced by abiotic factors, as these factors can affect the growth, reproduction, and survival of the individuals within the population. Hence, populations are related to abiotic factors.
4. **Ecosystem**: An ecosystem includes both biotic (living organisms) and abiotic (non-living elements) components interacting with each other. Ecosystems are heavily influenced by abiotic factors such as temperature, water, and nutrients, making them highly dependent on these factors.
Based on this analysis, the ecological unit or relationship that is least related to abiotic factors is **symbiosis**.
### Step-by-Step Solution:
1. **Identify the ecological units**: Understand the definitions of community, symbiosis, population, and ecosystem.
2. **Analyze the relationship with abiotic factors**: Consider how each unit interacts with abiotic factors.
3. **Compare the level of dependence**: Evaluate which unit has the least dependence on abiotic factors.
4. **Conclude**: Determine that symbiosis is the least related to abiotic factors.
