Oxpeckers land on rhinos or zebras and eat ticks and other parasites that live on their skin. The oxpeckers get food and the beasts get pest control. Organisms in a symbiotic relationship evolved together. The bee and the flower.
Bees fly from flower to flower gathering nectar, which they make into food, benefiting the bees.
This benefits the plants. In this symbiotic relationship, the bees get to eat, and the flowering plants get to reproduce. The spider crab and the algae. Spider crabs live in shallow areas of the ocean floor, and greenish-brown algae lives on the crabs' backs, making the crabs blend in with their environment, and unnoticeable to predators. The algae gets a good place to live, and the crab gets camouflage.