1. Consumers Producers Sunlight
Mangrove's ecosystems
Consumers
Producers
Sunlight

2. question/claim
How can you use a model to describe that energy in animals’ food was once energy from the sun?
The energy in animals' food was once energy from the sun.

3. producers/consumers Sunlight Producer: a mangrove (flora)
First Consumer: mangrove crab
Second Consumer: small fish (silver perch)
Third (final) Consumer: pelican 

4. What eats what? The mangrove (flora) get its energy from the sunlight
The mangrove crab eats the flora and the crab now has its energy
The small fish (silver perch) eats and gets its energy from the crab
The pelican eats the small fish 

5. Reasoning
As you can see, the food chain is how everyone gets food and their energy. Sunlight is the most important part and the start of the food chain!