- Producers are a source of food energy in an ecosystem
- Living things are a part of an ecosystem
- Therefore, producers are a source of food energy for living things

- Living things all require energy for survival
- If something requires something else then that something requires a source of that something else
- Therefore, living things all require a source of energy for survival

- Producers are a source of food energy for living things
- Living things all require a source of energy for survival
- Therefore, living things all require a producers for survival

- Living things all require a producers for survival
- If a living thing requires something for survival then that living thing is dependent on that something
- So, all living things are dependent on producers

- Green plants provide food for themselves / animals / consumers by performing photosynthesis
- To provide something can mean to produce something
- Therefore, green plants produce food for themselves / animals / consumers

- Green plants produce food for themselves / animals / consumers
- A producer produces its own food
- Therefore, green plants are a kind of producer

- All living things are dependent on producers
- Green plants are a kind of producer
- Therefore, all living things are dependent on plants because plants are a kind of producer

Therefore, all living things are dependent on plants because plants are a kind of producer
All living organisms are dependent on plants because plants
- Green plants provide food for themselves / animals / consumers by performing photosynthesis 
- Producers are a source of food energy in an ecosystem 
- A producer produces its own food 
- To provide something can mean to produce something 
- Living things are a part of an ecosystem 
- If a living thing requires something for survival then that living thing is dependent on that something 
- Living things all require energy for survival 
- If something requires something else then that something requires a source of that something else