The introduction is written in present tense and provides a general review of information on the subject of the experiment. It is common for the introduction section to start with the broadest statements about the area of the study and become more specific. The introduction should contain adequate material so that the objective and significance of the current experiment can be understood. The information from published works provides the framework from other experiments which are relevant to the research described in the report. Textbooks and scientific journals can serve as the basis for the information presented in the introduction. Supporting material for this section can also be drawn from the internet. Any websites used to gather this information should be trusted and reliable. Two primary groups of internet sites which can provide valid information are governmental websites and internet sites maintained by universities or other academic institutions. When possible, any information from internet sources should be verified. Scientific articles from online publications are cited as written journals if the electronic version is also available in print.
Citations should follow the sentence which contains the material referenced in the report. The reference citation includes the last name(s) of the author(s) and the date of the reference (see examples in the reference pre-lab).
When a citation has more than two authors, the last name of the first is listed, followed by et al. to indicate the additional authors. An example of this type of citation is:
Introductions to research papers also state the hypotheses which are being tested, as well as the scientific rationale for testing these hypotheses. The example study referred to in this pre-lab section could have the following stated hypothesis:
The introduction may also include a statement on the purpose of the experiment, such as:
This example represents the full introduction section from the research paper referred to thus far:
Light is required for plant growth and survival. Plants have photosynthetic pigments that absorb light energy and convert it into chemical forms such as ATP. This process is called photosynthesis. The transduction of solar, or light, energy into chemical energy is often expressed in terms of carbon dioxide fixation, in which hexose is formed from carbon dioxide and oxygen is produced (Garrett and Grisham, 2010). A simplified version of the reaction can be written:
The first pathway of photosynthesis, called the light reactions, occurs in the thylakoid membranes of the grana. During these reactions light energy is absorbed by the photosynthetic pigments, mainly chlorophylls, and is used to form ATP and NADPH molecules (Raven et al. 1992). As a result, the oxygen atoms of water molecules in the chloroplasts are oxidized to produce O2 (Falkowski and Raven, 1997; Hill, 1939; Kirk, 1994). The oxygen produced during the light-driven reactions passes out of the stomata found in the lower surfaces of plant leaves. The second pathway of photosynthesis, called the Calvin-Benson cycle reactions, occurs in the stroma, a fluid-filled space. During these reactions, CO2 is fixed and reduced to sugar (Calvin, 1962). The energy to drive the second pathway comes from products of the first pathway. The rate of oxygen production can therefore be used to estimate the rate of photosynthesis (both pathways combined).
Reduced water clarity can affect submerged plants by reducing light intensity levels below those required for optimum growth. The required light intensity for growth is different for different plant species. Elodea canadensis is a plant which lives completely underwater. It is native to North America and grows in lakes, ponds and sheltered areas of rivers. It also is widely used in aquariums.
The purpose of this study is to determine the effect of light intensity on the rate of photosynthesis in Elodea canadensis sprigs as determined by the rate of oxygen bubble production. It is hypothesized that the rate of photosynthesis increases as the light intensity increases. If the hypothesis is true, more oxygen bubbles will be produced at higher light intensities than at lower intensities. This data will be discussed in terms of the clarity of the water in the University Lake system.