Stratification refers to the vertical distribution of different species occupying different levels within an ecosystem. It is an important concept in ecology and helps to understand the organization and structure of biological communities.

Vertical Distribution of Different Species
The correct answer, option 'A', best describes the term 'Stratification' as the vertical distribution of different species occupying different levels within an ecosystem. This means that within an ecosystem, different species are found at different vertical levels or strata, based on their specific ecological requirements.

Explanation of the Answer
Stratification is a common phenomenon in various ecosystems, including forests, aquatic habitats, and even grasslands. In a forest ecosystem, for example, different species of plants and animals are found at different vertical levels. The tallest trees make up the canopy layer, followed by the understory layer, shrub layer, and forest floor. Each of these layers has a distinct set of species adapted to the specific conditions and resources available at that level.

Importance of Stratification
1. Resource Utilization: Stratification allows for efficient utilization of resources within an ecosystem. Different species occupy different levels and have specific adaptations to utilize available resources effectively. This reduces competition between species and increases overall productivity.

2. Biodiversity: Stratification contributes to biodiversity by creating diverse habitats within an ecosystem. Different levels provide a variety of microhabitats, which support a wide range of species with different ecological requirements. This enhances the overall biodiversity and ecological resilience of the ecosystem.

3. Trophic Interactions: Stratification also influences trophic interactions within an ecosystem. Different levels support different primary producers, herbivores, and predators, creating complex food webs and energy flows. These trophic interactions are essential for maintaining the balance and stability of the ecosystem.

Examples of Stratification
1. Forest Ecosystem: As mentioned earlier, a forest ecosystem exhibits clear stratification. The tallest trees form the canopy layer, which receives the maximum sunlight. Below the canopy, there is the understory layer, followed by the shrub layer and forest floor. Each layer supports a unique set of species adapted to the specific light, temperature, and nutrient conditions.

2. Coral Reef Ecosystem: Coral reefs also display stratification. The reef-building corals occupy the uppermost layer, where they have access to sunlight for photosynthesis. Below the corals, there are various organisms such as algae, sponges, and sea fans. Finally, at the bottom, there are the substrate-dwelling organisms like sea cucumbers and sea urchins.

Conclusion
Stratification refers to the vertical distribution of different species occupying different levels within an ecosystem. It is an important concept in ecology as it helps to understand the organization and structure of biological communities. Stratification allows for efficient resource utilization, enhances biodiversity, and influences trophic interactions within an ecosystem. Examples of stratification can be observed in forest ecosystems, coral reefs, and various other habitats.