Step 1: Understanding the Concept
Ecosystems provide services such as pollination, pest control and nutrient cycling.
Step 2: Link to the question
Crop production and fruit formation depend on pollen transfer by insects, birds and other agents.
Step 3: Conclusion
The service is pollination.
Final Answer:
Pollination is the service required for fruit formation.
\[ \boxed{\text{(D) }\text{Pollination}} \]