The document discusses the key parts and functions of leaves. It explains that leaves contain chlorophyll which makes them appear green. Leaves have a blade and veins which transport substances like water and minerals. Stomata on the lower leaf surface allow plants to breathe. Leaves act as the food factory of plants, manufacturing food through photosynthesis using sunlight, water and carbon dioxide. Photosynthesis produces oxygen and sugar as a byproduct, with the sugar transported through the plant. Plants and animals depend on each other, as plants produce oxygen for animals and animals produce carbon dioxide for plants. Food chains demonstrate how each organism depends on others as a source of food.