photosynthesis makes food for the plant & a leaf performs photosynthesis / gas exchange ->  a leaf makes food for the plant by performing photosynthesis  a leaf makes food for the plant by performing photosynthesis & providing food is a kind of specific life process ->  a leaf performs a specific life process of making food for the plants  a leaf performs a specific life process of making food for the plants & organs perform specific life process in organisms -> a leaf in a plant is performing like an organ in organisms