Praxis Biology Content 5235 Practice Questions and Answers

The independent variable in an experiment is the one thing that is varied between experimental groups. The effect of the independent variable is typically what is being analyzed. In the situation described, the independent variable is the method by which the passage is presented to the test subjects, either aurally or visually. continuous variation Human skin color, height, and weight are influenced by many genes as well as environmental factors. When the frequency in a population of different values for each one of these traits is plotted on a histogram, a bell shaped curve of continuous variation usually results. The values of a few individuals are at either end of the curve; the values of most individuals are intermediate and fall in the middle of the curve. complete dominance a relationship in which one allele is completely dominant over another polyploidy condition in which an organism has extra sets of chromosomes pleiotropy The ability of a single gene to have multiple effects. Which of the following best describes scientific evidence? Scientific evidence is data gathered from experiments or observations to address a specific hypothesis. The data may help to support or reject the hypothesis. Louis Pasteur performed a now classic experiment to test the hypothesis of spontaneous generation. He placed meat broth in each of two flasks with S shaped necks. He boiled the broth in both flasks to sterilize it and then broke off the S shaped portion of the neck from one flask. The broth in the flask that now had a straight neck became cloudy, while the broth in the flask with the S shaped neck remained clear because any airborne organisms were trapped in the neck of the flask. Which of the following substances should be added to an acid spilled on a lab bench in order to safely neutralize the acid before cleaning up the spill? A spill of most acids used in school laboratories can be neutralized by shaking sodium bicarbonate (baking soda) onto the spill. After any bubbling or fizzing has stopped, the pH of the solution can be checked with pH paper. When neutralized, the spill should be carefully wiped up and the surface cleaned thoroughly.