The following example is the opening paragraph of an article in Animal Behaviour about begging behaviour among young meerkats. 

Example:

Begging provides offspring with benefits in the form of 'free food' (reviewed in Wright & Leonard 2002). Such benefits to offspring occur at a cost to the adults that provide the food (Pugesek 1990; Wheelwright et al. 2003). This produces a conflict of interest between the offspring and the adults (Trivers 1974), such that offspring are expected to benefit from extending their begging period and attendant food supply, while adults benefit from stopping providing food to begging offspring. Eventually, all offspring cease demanding ‘free food’ and stop begging. Why do individuals stop begging, and so lose a low-cost source of nutrition? Three mechanistic explanations have been suggested, and these could apply to either vocal or nonvocal begging displays.

(Madden et al., 2009, p. 85)

A closer look at the sentences that make up the paragraph will reveal its structure:

Topic sentence

The topic of the paragraph is stated in an introductory topic sentence:

Begging provides offspring with benefits in the form of 'free food' (reviewed in Wright & Leonard 2002).

Comment: This sentence catches the essence of the paragraph and directs the reader to the issue under discussion - begging behaviour in young animals.

Supporting sentences

What is stated in the topic sentence is then followed up by three supporting sentences:

Such benefits to offspring occur at a cost to the adults that provide the food (Pugesek 1990; Wheelwright et al. 2003). This produces a conflict of interest between the offspring and the adults (Trivers 1974), such that offspring are expected to benefit from extending their begging period and attendant food supply, while adults benefit from stopping providing food to begging offspring. Eventually, all offspring cease demanding 'free food' and stop begging.

Comment: The first and the third supporting sentences ("Such benefits to offspring occur..." and "Eventually...") provide further information and clarification, whereas the second supporting sentence ("This produces...") offers an example of the statement that has been presented.

Concluding sentences

The last two sentences of the paragraph conclude the argument:

Why do individuals stop begging, and so lose a low-cost source of nutrition? Three mechanistic explanations have been suggested, and these could apply to either vocal or nonvocal begging displays.

Comment: The question-and-answer structure of the concluding part of the paragraph sums up what was suggested in the topic sentence. These concluding sentences also create a transition to the following paragraph, where the three explanations referred to will be discussed.