Example of Introduction

COMMUNICATION IN THE BIOLOGICAL SCIENCES
Department of Biology

AN EXAMPLE OF AN INTRODUCTION

Although the water economies of a number of species of amphibians have been studied, the majority of these investigations have been interspecific in nature (Smith et al. 1998). Such studies have often sought to elucidate adaptive differences among species inhabiting different habitats (Thorson and Svihla 1943, Littleford et al. 1947, Thorson 1955, Schmid 1965, Farrell and MacMahon 1969, Ralin and Rogers 1972, Gillis 1979). Comparable adaptive differences may also occur between developmental stages of a single species, especially when these stages occur in different environments. However, correlations between developmental stage and ecophysiological parameters have been relatively unstudied.

The red-spotted newt (Notophthalmus viridescens) has a more complex life cycle than many amphibians. In most amphibians, an aquatic larval stage is followed by the adult stage that occurs in either aquatic or terrestrial habitats. In this species, however, larvae develop rapidly and metamorphose into terrestrial salamanders, the red-efts. After spending up to seven years in terrestrial habitats, these subadults go through a second metamorphosis to become aquatic adults (newts) that spend the remainder of their lives in water (Conant 1975).

In view of the difference in habitats occupied by these two stages it was hypothesized that newts and salamanders should differ in terms of their water economy. Specifically, terrestrial efts should have lower rates of evaporative water loss and be more tolerant to dehydration than aquatic newts.

Comments:

Note how the introduction started with a relatively broad idea (water economies in amphibians) and that it identified a general "hole" in the literature (that most studies have studied interspecific patterns -- that is, "among-species" patterns rather than "within-species" patterns).
In paragraph 2, note that the topic is narrowed to introduce the species studied in this investigation.
The final sentences of the Introduction state the hypotheses considered in this study.
Thus, the Introduction looks like an upside-down triangle -- broadest topic at the top and progressively narrows to a "point" which is the statement of specific hypotheses or objectives.
Also note that the Introduction includes a number of citations to primary literature.

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