Environmental Problems, Their Causes, and Sustainability 1

and hold moisture and mineral nutrients used by bothspecies. The algae, through photosynthesis, providesugars as food for themselves and the fungi.A mutualistic relationship that combines nutritionand protection is birds that ride on the backs of largeanimals like African buffalo, elephants, and rhinoceroses(Figure 8-10a). The birds remove and eat parasitesfrom the animal’s body and often make noises warningthe animal when predators approach.Another example is clownfish species, which livewithin sea anemones, whose tentacles sting and paralyzemost fish that touch them (Figure 8-10b). Theclownfish, which are not harmed by the tentacles, gainprotection from predators and feed on the detritus leftfrom the meals of the anemones. The sea anemonesbenefit because the clownfish protect them from someof their predators.Another example of nutritional mutualism is thehighly specialized fungi that combine with plant rootsto form mycorrhizae (from the Greek words for fungusand roots). The fungi get nutrition from the plant’sroots. In turn the fungi benefit the plant by using theirmyriad networks of hairlike extensions to improve theplant’s ability to extract nutrients and water from thesoil (Figure 8-10c).In gut inhabitant mutualism, vast armies of organismssuch as bacteria live in an animal’s digestive tract.The bacteria receive a sheltered habitat and food fromtheir host. In turn, they help break down (digest) theirhost’s food. Examples are the bacteria inside a termite’sgut that digest wood or cellulose and providethe termite with food. Similarly, bacteria in your guthelp digest the food you eat. Thank these little crittersfor helping keep you alive.(a) Oxpeckers and black rhinoceros(b) Clownfish and sea anemone(c) Mycorrhizae fungi on juniper seedlingsin normal soil(d) Lack of mycorrhizae fungi on juniperseedlings in sterilized soilFigure 8-10 Examples of mutualism. (a) Oxpeckers (or tickbirds) feed on and remove parasitic ticksthat infest large thick-skinned animals such as a black rhinoceros. (b) A clownfish gains protection andfood by living among deadly stinging sea anemones and helps protect the anemones from some oftheir predators. (c) Beneficial effects of mycorrhizal fungi attached to roots of juniper seedlings on plantgrowth compared to (d) growth of such seedlings in sterilized soil without mycorrhizal fungi.http://biology.brookscole.com/miller14155