A textbook model says a plant's added mass comes mainly from the soil. Students seal a pot, and after the plant gains 40 g the soil has lost only 1 g. What should they do with the model?

A lake's summer fish deaths have long been explained by low oxygen alone. New sensor records show the deaths begin about two weeks before oxygen levels start to fall each year. What does this evidence support?

A company claims its fertilizer makes corn taller. In a fair test with the same soil, water and light, fertilized plots had a mean height of 148 cm and untreated plots 147 cm. What does this evidence support?

Doctors once taught that stomach ulcers are caused only by stress. Later work found a stomach bacterium in most ulcer patients, and antibiotics that removed it healed the ulcers. What should be done with the stress-only explanation?

A group's water cycle model shows water moving only from ocean to cloud to rain and back to the ocean. Field data show water also leaving leaves as vapor and soaking down into groundwater. What should the group do?

A class accepts that their pond is warmest at noon. Sensor data give 09:00 = 18 C, 12:00 = 21 C, 15:00 = 24 C, 18:00 = 22 C. What conclusion does the data support?

For years the frogs at one pond were counted by listening at night. New night cameras record two frog species at the pond with almost identical calls. How should the old counts be treated?

An accepted claim says a beach is growing. Surveys of the same line give 2019: 41 m wide, 2021: 38 m, 2023: 35 m. What should scientists conclude?

In the 1950s Marie Tharp worked on maps of the Atlantic sea floor without going to sea herself. What did she do to build those maps?

In 1936 the Danish seismologist Inge Lehmann studied earthquake wave recordings made at stations far from the earthquake. What did those recordings lead her to propose about Earth?

In 1856 Eunice Newton Foote put a thermometer inside each of several glass cylinders holding different gases and set them in sunlight. What did her measurements show?

In the 1670s Antonie van Leeuwenhoek ground tiny glass lenses and mounted them in small brass frames. What did he report after examining water from a lake near Delft?

At the Tuskegee Institute experiment station, George Washington Carver tested planting peanuts and cowpeas on fields worn out by cotton. What did his field results show about those crops?

Charles Henry Turner trained honeybees to feed at colored paper disks and at cards printed with different patterns. What did his experiments show about the bees?

Scientific knowledge is called durable because it rests on large amounts of evidence, even though new evidence can still change it.

When scientists revise an explanation, they can ignore all the evidence that supported the old one.

Two teams measure a river's oxygen at the same site and get the same numbers, but they publish different explanations for a fish die-off. What best explains their disagreement?

A student says an explanation that scientists later revised was 'just wrong all along'. Why do scientists still call the earlier explanation useful?

An old classroom poster shows a cell with three parts. A newer poster shows several more parts, drawn from images made with stronger microscopes. What does the difference show?

Two research teams study the same tree rings and report different rainfall amounts for one past decade. What is the best next step for both teams?