& Data Analysis
Protein gel electrophoresis
Protein gel analysis
Concepts and theory
Writing Samples – Parts of a Research Paper
Title and introduction
Below are two examples of a title and introduction to the same research paper. Which writing sample is the better one, and why? Based upon the general guidelines for an introduction as well as your own experience give the "bad" one a letter grade and prepare a set of brief comments explaining the grade. Compare your grade and comments with the analysis presented below. Citations are omitted for brevity.
Title: Lab report #3
Understanding the differences between sun and shade leaves is an important goal in cell biology.
Title: Morphological adaptations by sun and shade leaves of Ligustrum japonicu
Selective pressure due to differences in intensity of available light from one habitat to another has clearly played an important role in speciation. Many plant species (sun plants) are adapted to thrive only in full sun, while others are not at all sun tolerant but thrive in full shade. Plants that in their native environment grow under very high light intensities are capable of significantly higher photosynthetic rates under saturating light intensities, while shade plants show higher rates of photosynthesis under shade conditions (1). Some differences, particularly related to surface area and thickness, are also correlated with an increased tolerance by sun plants of intense solar radiation and of dessicating conditions (4). To fully understand the role of sunlight in determining diversity of plant species in a given ecosystem it is necessary to examine the structural features responsible for the physiological differences between sun and shade plants.
The leaves of many plant species that are adapted for full sun conditions share quantitative structural features that are distinguish them from leaves of shade plants (1). For example, leaves of typical sun plants have significantly smaller surface area than that of leaves from typical shade plants (2, 3). Sun leaves have been described as thicker than shade leaves with proportionally larger spongy and palisade mesophyll layers as well as thicker non-cellular waxy coatings. Such leaves typically contain a lower proportion of chlorophyll b relative to that of chlorophyll a, a higher content of total chlorophyll proportional to fresh weight, and higher RuDP carboxylase activity when normalized for fresh weight, leaf area, or chlorophyll content (1). Leaves of sun plants tend to have more stomata per unit surface area (4). Comparisons of light-related morphological differences have been limited to sun versus shade species, leaving open the question of adaptation of individual plants of a single species to different habitats.
The common wax-leaf ligustrum (L. japonicum) is an evergreen srhub that is capable of growing in both full sun and in deep shade. This study sought to determine which structural features typify sun or shade plants also typify sun- or shade-grown ligustrum leaves. The chlorophyll content and RuDP activity of both types of leaves were compared, as were surface area, fresh weight per unit surface area, and overall thickness. The respective thicknesses of spongy and palisade mesophyll layers and number of stomata per unit surface area were compared between the two types of leaves. These data were used to determine which, if any, of the features shared by sun or shade plant species characterize the adaptation of ligustrum leaves to full sun or deep shade conditions.
Analysis (Exhibits A and B)
Let's start with exhibit B. There are many ways to write an introduction to the same article. This approach worked because the author accomplished several goals in a relatively brief space. First, the author established a context . The work is identified as related to understanding the evolution of plant species and the role of sunlight in creating diversity. Background information in the second paragraph provides the rationale for the objectives of the study and a basis for the experimental design. The experimental model, wax-leaf ligustrum, is described briefly in a paragraph that describes how the study accomplished the objective. For some studies an entire paragraph might be dedicated to defending the choice of model organism, however such defense was probably not necessary in this case. Because ligustrum is a common landscape shrub and is evergreen it is inexpensive, and widely available at all times of the year. One could add those statements but they probably aren't necessary.