I then distributed a selection of items to their desks: a bowl of speckled minnows, a glass of clear tap water, a jar of murky pond water, a rock, an aloe vera plant. “Are they alive? How do you know?”

Drawing on the students’ own experiences and reasoning as they categorized each object, we defined a list of characteristics common to living things. Then, we compared our list to that of modern scientists. We discovered that the movement my students noted as a sign of life in animals is one of many ways in which living things respond to stimuli. Similarly, while some organisms eat, and others photosynthesize, all living things gather matter and energy.

The second week of school, we approached my second foundational question: “What is science?”

After reading a short biography of John James Audubon, we considered how he went about studying birds of North America. He sat in a cave for weeks with Eastern Phoebes. He collected specimens, sketched, and painted endlessly. He designed a simple experiment to identify whether the birds he’d observed throughout the summer returned to those same nests the following spring. We then compared Mr. Audubon’s work to a definition of science proposed by author John Mays: “Science is the process of using observation, experimentation, and logical reasoning to develop theories about the natural world.”

In the weeks since school began, we have additionally looked at contributions of Francisco Redi, Louis Pasteur, and Alexander Fleming. I love using biography to teach science, because the lives of scientists provide clear depictions of the acts of science. Observation, experimentation, and logical reasoning are the substance that makes up each of their stories.

With biography in mind, I have made Mays’s one-sentence definition a guideline for my lesson plans. While it is important to learn the facts and definitions of science, the content of the subject, it is equally essential that students develop the habits and skills of the work of science.

This year we will observe, experiment, and reason through studies, from microscopic protozoa to the cardiovascular system of mammals.

Observation looks like a tray of hexbugs, a bowl of fish, a jar of pond water, and the first mushrooms that come with fall rain. Experimentation is watching this morning’s balloons, inflating with carbon dioxide produced by yeast fermenting sugar mixed with tepid water, though not so well with cold or hot water. And invitation to reason continues as from the very first homework question of the semester: “Is fire alive? Describe in what ways fire does or does not meet the characteristics of living things.”