Here's how it works:

* Sunlight: They capture sunlight using chlorophyll, a green pigment found in their chloroplasts.

* Carbon Dioxide: They absorb carbon dioxide from the surrounding water or air.

* Water: They take in water through their cell membranes.

* Photosynthesis: Chlorophyll uses sunlight to convert carbon dioxide and water into glucose (sugar) and oxygen.

* Glucose: This is their energy source for growth and reproduction.

* Oxygen: This is released as a byproduct.

In essence, green algae are like tiny solar panels, converting light energy into chemical energy (glucose) for their own use.