School Improvement in Maryland

Evolution of an Item

Science

  

These are examples of items in their original form and the suggested revisions to make the item more accessible for students. Further explanation and examples can be found at Biology Assessment in the Instruction section of this Web site.

Example #1

ORIGINAL (less accessible)

A student wanted to perform an experiment using chlorophyll that has been extracted from spinach leaves. The leaves were macerated and mixed with 50 mL of 95% ethyl alcohol. The chlorophyll was then extracted by boiling the mixture in a hot water bath for five minutes. What procedures and equipment should the student use for laboratory safety? Please explain.

BETTER

It is important for every student to follow safe procedures in the laboratory. Use you knowledge of laboratory safety to answer the following question.

A student wants to do an experiment using chlorophyll, the green pigment in leaves. To obtain the chlorophyll, she chops some spinach leaves into small pieces. Next, she places the leaves and some alcohol into a small beaker. She then places the smaller beaker into a container of boiling water, and heats it on a hot plate for five minutes.

  • What steps should this student take to demonstrate laboratory safety?
  • What equipment should she use to perform a safe experiment?

Example #2

ORIGINAL (less accessible)

In the fruit fly, Drosophila melanogaster, individuals may express the long-winged trait (L) or the short-winged trait (l). What would be the expected ratio of expressed traits in the F1 generation of a cross between two parent fruit flies that are heterozygous for long wings and homozygous for short wings?

BETTER

In fruit flies, the form of the gene for long wings (L) is dominant. The form of the gene for short wings (l) is recessive. A scientist crosses a heterozygous long-winged fruit fly with a homozygous short-winged fruit fly. Predict the expected ratio of long to short wings in the offspring.