Question

The first trophic level in a food chain is always occupied by green plants. Why?

Answer 1

Food chain is like
1. Producer
2. Consumer
3. Sec.Consumer
Plants are the only producer in this world as in every food chain you can see in
1. Grass
2. Grasshopper
3. Toad
4. Snake
There are other examples of food chain like
grass -> deer-> Lion
In all cases some type of plant is present at the first level to produce food then that food is eaten by some consumer and then it is eaten by some other sec.consumer
Another example is in aquatic field like
Plankton(a sea plant) -> Whale -> Humans.
I this will be enough for you and hope that it helps

Answer 2

Answer:

This is because producers absorb sunlight and fix it into food chain. This energy is transferred to organisms.