A partial grassland food web is shown. Which of the following best describes a relationship in this grassland?

For a laboratory investigation some students put a strip of shiny metal into a beaker of blue solution and then stored the beaker on a shelf overnight. The next morning, the students recorded observations about the metal and the solution in the box below. Based on their observations, can the students correctly conclude that a chemical reaction occurred?

Which statement describes the energy changes that occur when water in a tea kettle is heated on a stove that uses natural gas?

The beginning of autumn in North America is in September, but the beginning of autumn in South America is in March. The diagram shows the positions of Earth, the moon, and the sun on one day in September and one day in March. Why does autumn start in different months of the year in North America and South America?

This drawing shows a human body system. What is the primary function of this body system?

The diagram of Situation 1 shows one person failing to move a refrigerator up a ramp, while the diagram of Situation 2 shows two people successfully pushing a refrigerator up a ramp. What comparison can be made about the work done in the two situations?

The photograph shows mountains in the Andes range in South America. Which statement describes the geologic process that is most likely responsible for the formation of these mountains?

A group of scientists studied some trees in a pine forest. In the densely forested areas, the trees were within 1 m of each other. The scientists observed that these trees had dead branches near the ground. They measured the height above the ground at which the first living branches were found on different-sized trees in the forest. Then they repeated this procedure on the same kind of trees in an open meadow. This graph summarizes the scientists’ data. Which inference is best supported by these data?

The picture shows an aerialist walking on a tightrope and holding a balancing bar.                              An action-reaction pair of forces exists between —

A student drew atomic models of four elements. Based on these drawings, which element is the least reactive?

A marble is given potential energy by being placed at Location W. When the marble is released, it rolls down the track. At which location does the marble have maximum kinetic energy?

A student models convection currents in a laboratory activity. How are the convection currents in the student’s model different from the convection currents in Earth’s atmosphere and oceans?

Darwin’s finches are a group of seed-eating bird species found on the Galápagos Islands. Nest flies are a type of insect that has become a threat to the finches. The diagram shows  the life cycle of the nest fly. Based on the life-cycle information, which statement best describes the relationship between the nest fly larvae and the young birds?

As part of an investigation, students combined substances in a beaker to observe chemical reactions. They performed two procedures. They measured the mass of each substance before and after each reaction. The table shows their observations. Assuming the students did not make any careless errors, what likely explains these changes in mass?

The house sparrow was first introduced to New York in 1851. It is now distributed across most of North America. As the species expanded its range, it began to live in environments that were different from its original habitat. The birds now vary in size, depending on their geographic location. The map shows the distribution of house sparrows by size. What is the most likely explanation for the body-size distribution of house sparrows shown on the map?

A student shows a model of Earth and the moon to a class. Which picture shows how the moon appears from Earth when it is in the position shown in this model?

This topographic map represents the elevation of an area 100 years ago. At that time the highest point had an elevation of 214 m. The highest point has since eroded a total of 7 m. Which profile most likely represents the landscape today?

A physics teacher performed a demonstration for a science class by pulling a crate across the floor and measuring the force with a spring scale. While she pulled, a student measured the acceleration of the crate with a handheld electronic device. The results of three trials are shown below. The teacher asked the class to calculate the acceleration of the crate based on the crate’s mass and the force she applied. What conclusion can be made about the difference between the calculated acceleration and the actual acceleration that occurred in the trials?

An energy pyramid is shown. Which sentence best describes how energy flows through this pyramid?

Students slid a small wood block along a flat tabletop for a distance of 1.6 m. The data show the motion of the block of wood. Which graph displays the motion of the wood block?