 Multiple inheritance channels may be involved in the reconstruction of the phenotype. For example, as noted in the discussion of cellular heredity, inheritance of organelles during cell division is required for the survival of daughter cells in addition to the inheritance of the nuclear genome. The role of multiple channels is particularly apparent in cases where phenotypes depend on symbiotic associations and thus on the transmission of symbionts. Examples of transmission of symbionts include: (1) The transmission of gut bacteria, which are required for digestion and for normal intestinal development, from mother to offspring. (2) Fungus-growing ants depend on the cultivation of fungus for food in underground gardens. When new queens leave their parent colonies, they carry a fragment of the fungus with them to the site of the new colony. (3) Various species of aphids, clams, and sponges allow some bacteria to pass through the oocytes from parent to offspring, leading to vertical transmission parallel to genetic transmission. As a final example of multiple channels of inheritance note that cultural transmission in humans and animals, which is required for the reconstruction of behavioral phenotypes such as bird songs, food preferences, and other cultural traditions (Avital &amp; Jablonka 2000), may also be considered to constitute supplementary inheritance channels.