1. Symbiotic Relationships
A relationship in which two different species live together and interact closely over a long period of time.

2. Mutualism Both species benefit from the relationship
Ex/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. Also, when there is danger, the oxpeckers fly upward and scream a warning.

3. Parasitism
One species (the parasite) benefits, while the other (the host) is harmed.
Ex/Tapeworms are segmented flatworms that attach themselves to the insides of the intestines of animals such as cows, pigs, and humans. They get food by eating the host's partly digested food, depriving the host of nutrients.

4. Commensalism
Only one organism benefits, the other is not helped or harmed.
Ex/The Shark and the Remora have a symbiotic relationship. The remora benefits from the shark’s presence, but the shark is unaffected. The Remora stays along for the ride to catch scraps of food from the shark’s meals, and clean off pieces of the meal from the shark’s body.

5. Other interactions..
Competition – Organisms compete with each other over limited resources (Ex/ food, mating rights, shelter..)
Predator-Prey – generally have a cyclical relationship (predator population rises, the prey population falls, then predator population falls and so on…)