1. A particular species of a unicellular organism inhabits the intestines of termites, where the unicellular organisms are protected from predators. Wood that is ingested by the termites is digested by the unicellular organisms, forming food for the termites.
Mutualism

2. Mistletoe grows on trees
Mistletoe grows on trees. It sends its roots into the tree and uses the nutrients that could otherwise be used by the tree. Therefore, the tree does not get to use all the nutrients and usually dies.
Parasitism

3. Lichen species are made up of a fungus that contains either a bacterium or an alga. The fungus protects the bacterium or alga, and the bacterium or alga provides food for the fungus.
Mutualism

4. An American Robin benefits by building its nest in a Red Maple tree
An American Robin benefits by building its nest in a Red Maple tree. The tree is unaffected.
Commensalism

5. Some ant species use excess plant sap for their own nutrition
Some ant species use excess plant sap for their own nutrition. These ants will find a colony of aphids and milk the waste plant sap from the cornicles. In return the ants protect the aphids from predators and parasites.
Mutualism

6. Barnacles live by using long, feathering appendages to sweep the surrounding water for small, free-floating organisms. The critical resource for barnacles is a place to stay. Barnacles attach to rocks, ships, shells, whales, and just about anywhere else they can gain a foothold.
Commensalism

7. The honey bee gets to eat the pollen from the flower
The honey bee gets to eat the pollen from the flower. The dandelion uses the bee to spread its pollen to another flower.
Mutualism

8. The tick gets food from the deer without killing it
The tick gets food from the deer without killing it. The deer is harmed by losing blood to the tick, and possibly by getting an infected wound.
Parasitism

9. Birds and mammals eat berries and fruit off of plants in the wild
Birds and mammals eat berries and fruit off of plants in the wild. The birds and mammals derive a food benefit by eating the berries and fruits. The plant, in turn, disperses it seeds.
Mutualism

10. Many species of moss or algae may live on the bark of a tree
Many species of moss or algae may live on the bark of a tree. The tree is completely unaffected and the moss or algae has a place to live.
Commensalism

11. Female mosquitoes ingest blood from humans and mammals for the protein to feed their larva. The saliva of the mosquito causes the skin to become irritated and itchy.
Parasitism

12. 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.
Mutualism

13. A few species of pseudo-scorpions disperse by concealing themselves under the wing covers of large beetles. The pseudo-scorpions gain the advantage of being dispersed over wide areas while simultaneously being protected from predators. The beetle is, presumably, unaffected by the presence of the hitchhikers.
Commensalism

14. Hookworms infect humans by residing in the small intestine and feeds off of the digested food in the small intestines. As the hookworm grows larger, the human slowly starves to death.
Parasitism

15. Assignment
Practice your marketing skills! Create an advertisement to “sell” your relationship. Pick one of the symbiotic relationships and come up with a visual and a catchy slogan.