Example: Bees and flowers. Bees collect nectar and pollen from flowers for food, while the flowers get help from the bees with pollination.
2. Commensalism- one species benefits, and the other species does not receive any benefits or is not harmed.
Example: Barnacles attached to a whale. The whale is unaffected by the barnacles, while the barnacles get a convenient place to live.
3. Parasitism- one species benefits at the expense of the other.
Example: Fleas on a dog. The fleas get food (blood) from the dog, while the dog gets irritated and may become anemic.