Monday

The course seedlings on the Windowsill have grown tall and lean hard toward the glass.

"They are reaching for the window," Rocket says. "Like they are hungry for it."

Raven measures the tallest one and writes the number. "What do you notice? We never fed them anything but water."

"Water is not food," Rocket says. "Where did all that green stuff come from?"

Nova hovers over the jar, her light bright and warm. "What comes through the window that does not come through the wall?" she asks.

"Light," Rocket says. "But you cannot eat light."

"A plant can do something with it that we cannot," Raven says, and underlines a new word in the Log: photosynthesis.

Some organisms can carry out photosynthesis and others cannot. An autotroph is an organism that can produce its own food.

The Greek roots of autotroph mean self feeder. Plants are the best-known autotrophs, but certain bacteria and algae are autotrophs too.

Heterotrophs cannot make their own food. They must get energy and carbon by consuming other organisms. The word means other feeder.

Humans are heterotrophs, and so are all animals. Even when an animal eats another animal, the food traces back to plants.

A deer gets energy by eating plants. A wolf that eats the deer gets energy that originally came from those plants.

Photosynthesis requires sunlight, carbon dioxide and water as starting reactants.

After the process is complete, photosynthesis releases oxygen and produces sugar molecules, most commonly glucose.

These sugar molecules contain the energy that living things need to survive. The plant builds itself and runs itself on them.

Photosynthesis also results in the release of oxygen into the air. To eat and to breathe, humans depend almost entirely on photosynthesizers.

Good thinking. Tomorrow you will go inside a leaf to find where the light is caught.