bottle, and a third worm with medium wet soil in another bottle, then put one bottle in the sun and the other two in the shade?” “No,” called out a student, “because the bottles in the sun would get hot and worms don’t like hot, that’s why they live underground, and you couldn’t tell whether it was the hot they didn’t like or how wet the soil was.” Ms. Flores used another group’s design for an investigation to assess whether other students understood this idea of a fair test.

Ms. Flores then asked the groups how they would know which place a worm “liked” the best. Students’ answers varied. One said if the worms grew bigger and had babies that was a sign they “liked” a place. Several said that if the worms died it meant they didn’t like something. Another suggested that if they set up an experiment where there were different options for the worms, where the worms crawled would tell you what they liked.

With a better understanding of what evidence to look for and how to prepare a fair test, the students were soon deep into their investigations. One group was studying the question of how earthworms have babies. They were busy examining the egg cases that they found in the soil using hand lenses and making drawings. They compared their drawings to those in books the librarian had brought to class for them and read about other characteristics of earthworms.

Two groups were exploring how the worms reacted to changes in their environment. They were struggling with how to deal with moisture, light, and temperature all at once. Ms. Flores asked some leading questions beginning with “what would happen if?” in the hope that the students would discover the value of studying one variable at a time. She would check on them later.

Another group wanted to know about the eating habits of worms. They decided to put slices of different fruits and vegetables into the soil and count the number of worm holes as evidence of what worms liked best. The two other groups set up a discarded ant farm with glass sides to observe the movement of worms in different kinds of soil.

Through the investigations and discussions of their observations, measurements, and library research, Ms. Flores’s students came to know more about the characteristics of worms, for example how they move, their eating habits, their life cycles, the characteristics of their environments, and their relationship to their environments. Their observations, combined with the research they did in library books, helped them understand why worms were not snakes or insects, but members of a phylum called annelid. They used the drawings and information in their lab notebooks to produce their own books, illustrated with drawings and

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