Autotrophs:
Green plants are considered autotrophs because they have the ability to produce their own food through the process of photosynthesis. This means they can convert light energy from the sun into chemical energy in the form of glucose.

Photosynthesis:
During photosynthesis, green plants use carbon dioxide, water, and sunlight to create glucose and oxygen. The chlorophyll present in their leaves helps in capturing sunlight, which is then used to convert carbon dioxide and water into glucose.

Importance:
Being autotrophs is crucial for the survival of green plants as they are able to sustain themselves without relying on other organisms for their food. This ability to produce their own food is what sets them apart from heterotrophs, which depend on other organisms for nutrition.

Role in Ecosystem:
Autotrophs, like green plants, play a vital role in the ecosystem by serving as the primary producers. They form the base of the food chain, providing energy to other organisms in the ecosystem. Without autotrophs, the entire ecosystem would collapse as there would be no source of food for other organisms.
In conclusion, green plants are called autotrophs because they have the unique ability to produce their own food through photosynthesis. This ability not only sustains the plants themselves but also plays a crucial role in maintaining the balance of the ecosystem.