Seasonal Affective Disorder (SAD) isn't directly an example of the relationship between biotic and abiotic parts of an ecosystem. Instead, it's an example of how abiotic factors can influence biotic factors (humans) through their impact on biological processes. Here's a breakdown:

* Abiotic Factor: The primary abiotic factor involved in SAD is light, specifically the decrease in sunlight during winter. The reduced sunlight affects the production of melatonin, a hormone that regulates sleep patterns.

* Biotic Factor: Humans, as part of the biotic world, are affected by this abiotic change. The lack of sunlight can disrupt their circadian rhythms and lead to the symptoms of SAD, such as low energy, mood changes, and difficulty sleeping.

Therefore, SAD demonstrates how a change in the abiotic environment (light) can have a direct impact on the biological processes of a biotic component (humans), leading to a change in their well-being.

It's important to remember that ecosystems are complex systems where everything is interconnected. The example of SAD highlights this interconnectedness, but it's not a direct example of biotic-abiotic interactions within a particular ecosystem.