Biology

Prokaryotes primarily take in carbon dioxide for photosynthesis through free diffusion.

Carbon dioxide is a small, nonpolar molecule. It can freely pass through the lipid bilayer of the prokaryotic cell membrane from an area of higher concentration (usually the surrounding environment) to an area of lower concentration (inside the cell) due to the concentration gradient. This is the most common and energy-efficient way for prokaryotes to take in carbon dioxide for use in the process of photosynthesis (specifically in the carbon fixation reactions like the Calvin cycle).

The other options are incorrect:

Active transport requires the expenditure of energy (usually in the form of ATP) to move substances against their concentration gradient. Carbon dioxide is a small, nonpolar molecule, and there is no need for the cell to use energy to actively transport it in, as it can move free...