NES Profile: Biology (305)

A scientist would like to determine the effect of night length on the flowering of the mustard plant Arabidopsis thaliana. Thirty of these plants will be randomly assigned to each of three experimental groups. The best rationale for including 30 plants in each experimental group is to:

1. minimize the effects of individual variations among the plants on the experimental results.
2. allow more conditions to be varied at once for each group.
3. reduce the chance that the scientist's expectations will bias the outcome of the experiment.
4. provide a sufficient number of plants for a control group.

Correct Response and Explanation (Show Correct ResponseHide Correct Response)

A. This question requires the examinee to demonstrate knowledge of the principles and procedures for designing and carrying out various types of scientific investigations. In sexually reproducing organisms, all individuals are genetically unique and thus vary in their characteristics. The inclusion of 30 plants in each experimental group, instead of just a few, provides a statistical measure of how much of the observed variation within a treatment group reflects individual variation among the plants rather than variation that is the result of the experimental treatment.

For which of the following reasons is the periodic table of the elements a useful model in science?

1. It lists the elements in order of their percent abundance in Earth's crust and atmosphere.
2. It organizes the elements into groups with shared chemical and physical properties.
3. It provides a historical record of the order in which the elements were discovered.
4. It separates the elements into three groups based on the state they are in at room temperature.

Correct Response and Explanation (Show Correct ResponseHide Correct Response)

B. This question requires the examinee to identify unifying scientific theories, models, and concepts in biology, Earth and space science, chemistry, and physics. Each column in the periodic table of the elements represents a group of elements with the same number of valence, or outer shell, electrons. This means that all the elements in a column are capable of forming the same number of chemical bonds and exhibit similar chemical behaviors. Elements are placed into rows, or periods, according to the number of shells occupied by their electrons, and are arranged across the table by increasing total numbers of electrons and atomic weights.

Which of the following advances in molecular biology has led to the most recent changes in vaccine development?

1. the manufacturing of vaccines that contain live pathogenic agents
2. the production of vaccines that allow transmission of lifelong immunity from one generation to the next
3. the synthesis of vaccines that provide lifelong immunity
4. the creation of vaccines composed of viral coat proteins that trigger immune responses

Correct Response and Explanation (Show Correct ResponseHide Correct Response)

D. This question requires the examinee to analyze the interrelationships between biology, engineering, technology, mathematics, and society. The ability to produce a vaccine composed only of viral coat protein antigens means that in the future vaccines could be genome-free. This reduces the risk of mutation to more dangerous viral forms that can occur in currently and previously available vaccines that consist of attenuated complete viruses.