Relationships between organisms that help one or both survive are called symbiotic relationships. There are three types of symbiotic relationships; mutualism, commensalism, and parasitism.
Mutualism
The white-tailed dove and saguaro cactus have a mutualistic relationship. The dove eats the seeds of the cactus. When it leaves, it deposits and spreads the seeds of the cactus around. The cactus benefits from the relationship by getting its offspring spread, and the white-tailed dove receives food. This is an example of mutualism because both species benefit from the interaction.
http://mbreiding.us/ert/Arizona/Rincons/nps.gov/sagu/www.nps.gov/sagu/saguaro_q_a/saguaroqa/doanimalsusesaguaros.htm
http://mbreiding.us/ert/Arizona/Rincons/nps.gov/sagu/www.nps.gov/sagu/saguaro_q_a/saguaroqa/doanimalsusesaguaros.htm
Commensalism
Commensalism is the relationship between animals when one benefits from the other, but the used organism is effected neither positively nor negatively. The cactus wren uses the cholla cactus to nest in. Because of the cactus' spines, the wren's babies are protected from predators. The cholla cactus is not affected by the use of it's defense mechanism.
http://conserveonline.org/workspaces/cacwnetwork
http://conserveonline.org/workspaces/cacwnetwork
Parasitism
Parasitism is the symbiotic relationship when one organism benefits from the use of the other, who is harmed by the parasite. Ticks are a prime example of a parasite. This tick is surviving off of the blood of a coyote. The tick benefits, but the coyote suffers because the tick transfers diseases.
http://king.portlandschools.org/files/houses/y2/animalmaineia/files/species/coyotebq/ecology/Ecology.html
http://king.portlandschools.org/files/houses/y2/animalmaineia/files/species/coyotebq/ecology/Ecology.html