Natural Experimental Combined
grasslands, heaths and forests have roots that have an intimate mutualistic association with fungi. Most corals depend on the unicellular algae within their cells, many flowering plants need their insect pollinators, and many animals carry communities of microorganisms within their guts that they require for effective digestion.
The rest of this chapter is organised as a progression. We start with mutualisms in which no intimate symbiosis is involved. Rather, the association is largely behavioral: that is, each partner behaves in a manner that confers a net benefit on the other. By Section 13.5, when we discuss mutualisms between animals and the microbiota living in their guts, we will have moved on to closer associations (one partner living within the other), and in Sections 13.6-13.10 we examine still more intimate symbioses in which one partner enters between or within another's cells. In Section 13.11 we interrupt the progression to look briefly at mathematical models of mutualisms. Then, finally, in Section 13.12 - for completeness, though the subject is not strictly 'ecological' - we examine the idea that various organelles have entered into such intimate symbioses within the cells of their many hosts that it has ceased to be sensible to regard them as distinct organisms.
Was this article helpful?