- The sun is the source of energy for life on earth
- Organisms are a kind of life on earth
- So, the sun is the source of energy for organisms on earth

- A beach is a kind of habitat / environment
- Environments are a part of earth
- Hence, a beach is a part of earth

- The sun is the source of energy for organisms on earth
- A beach is a part of earth
- Therefore, the sun is a source of energy for organisms on a beach

Hence, the sun is a source of energy for organisms on a beach
Question: What is the primary source of energy for organisms from a beach ecosystem?
Context: - The sun is the source of energy for life on earth 
- A beach is a kind of habitat / environment 
- Organisms are a kind of life on earth 
- Environments are a part of earth