RC1 Review

In a student experiment, 4 earthworms were placed at each end of a compartment as shown. After 10 minutes, all of the earthworms were together in the same area. The students concluded that the earthworms had moved as far as they could in that period of time. Which alternative explanation is also supported?

• The earthworms moved to their ideal temperature range
• The earthworms needed to be with other earthworms for warmth
• The earthworms preferred to be in protected corners
• The earthworms moved randomly until they were grouped together

A scientist observes that a species of insect appears to be more numerous during dry summers than during wet summers. Which is the next step to determine an explanation of this phenomenon?

• Develop a hypothesis
• Publish the observation
• Observe the species in the winter
• Present a theory in a scientific journal

Many residents in a small town have developed a bacterial infection. Two students hypothesize that the bacteria are coming from the town's drinking water. They look for the bacteria in water samples from the lake that supplies 80% of the town's drinking water. Which is a source of error in the experimental design?

• Water from the late was not tested for other possible pathogens
• Residents of other nearby towns were not tested for the bacteria
• The residents' genetic predisposition for getting ill was not determined
• Other sources of drinking water were not tested for bacteria

A student plans to conduct an experiment to determine how a change in the pH of water affects the population growth of algae. To ensure that her experimental data are valid, she should-

• hold the acidity of the water constant
• vary the temperature of the water used
• control the final algae population sizes
• use the same species of algae in all trials

The graph shows the populations of ladybugs and the red mites on which they feed. On which date did the ladybug population begin to exceed the red mite population?

• June 6
• June 10
• June 14
• June20

A student constructs several terrariums like the one shown. Each terrarium is exposed to a different amount of sunlight each day. In order to determine the ideal amount of sunlight, which of the variables must be held constant?

• Type of plants
• Growth rate of plants
• Wavelengths of sunlight
• Amount of sunlight received

As part of an experiment to measure decomposition rates of different materials, students put food scraps from the cafeteria in compost bin A and leaves and grass clippings in compost bin B for six weeks. Students in first period measured the temperature in bin A, and students in 6th period measured the temperature in bin B. What is the GREATEST error in the experimental design?

• There are too many uncontrolled variables in the experiment
• Temperature is the only dependent variable in this experiment
• The materials chosen decompose too rapidly
• The students put equal masses of materials in each bin

Scientists are using genetic engineering to develop a wheat crop that is resistant to a particular kind of moth. How would they determine if the plants are moth-resistant?

• Determine the length of the moth reproductive cycle in normal wheat
• Determine whether moths in test wheat can be controlled with chemical sprays
• Monitor numbers of moth species infesting normal wheat
• Monitor moth populations in fields planted with test and normal wheat

The diagram shows a setup for a plant investigation. Which variable is most likely being tested?

• Hours of light exposure
• Plant species
• Soil volume
• Soil pH

Twenty cuttings were taken from one plant and planted in four containers of sand. Two containers had a pH of 6.0, and two had a pH of 8.0. When the cuttings matured, all of those grown in the 6.0 had pink flowers, and all of those grown in a pH of 8.0 had blue flowers. One explanation for these results is that the sand at one pH contained a due that changed the flower color. The BEST alternative explanation for these results is that-

• the difference in pH caused the genes for flower color to be expressed differently
• a mutation occurred in the plant before the cuttings were taken and caused the difference
• by mistake, the scientist took some cuttings from the wrong plant
• by random chance, difference flower colors developed on the plants grown at different pH