The graph shows a yeast population growing in a sealed flask over 20 hours. Which statement best describes what happens to the population after hour 12?

The table shows how much product a digestive enzyme formed at five different pH values in 10 minutes. At which pH does this enzyme work best?

The graph shows the dissolved oxygen measured in stream water at five temperatures. What relationship does the graph show?

The table shows counts of snowshoe hares and lynx in one forest over four years. Which statement is best supported by the data?

The diagram shows feeding relationships in a meadow. If a disease removed all the snakes, what is the most likely immediate effect?

A sealed clear chamber holds a green plant in bright light. The graph shows the carbon dioxide inside it over 40 minutes. Which explanation best fits the data?

The table shows the resting pulse and the pulse after a three-minute run for four students. Whose pulse increased by the greatest number of beats per minute?

The graph shows the estimated human population from 1900 to 2020. What does it show about the rate of increase?

A student counted gas bubbles released by an Elodea sprig each minute: 5 at low light, 12 at medium light, 22 at high light and 23 at very high light. What conclusion do these results best support?

Field 1 received Fertilizer A and yielded 4200 kilograms per hectare. Field 2 received Fertilizer B and yielded 5600 kilograms per hectare, but Field 2 also received twice as much rain. What is the strongest claim the data supports?

Three unknown solutions were tested with Benedict's solution and with iodine. The table shows the results. Which sample contains starch but no simple sugar?

A student centers a specimen under the low-power objective and then switches to high power. What happens to the field of view?

A student tests whether a fertilizer speeds plant growth. Ten plants get fertilizer and ten identical plants get none, with light, water and soil kept the same for both groups. Which feature makes the results trustworthy?

The graph shows the activity of the enzyme catalase measured at six temperatures. What best explains the sharp fall in activity above 40 degrees Celsius?

When preparing a wet mount, a student lowers the coverslip slowly at an angle onto the drop of water. Why is the coverslip lowered this way?

The diagram shows the body's response to a rise in core temperature. What does this pattern of response illustrate?

Several hours after a meal, a person's blood glucose level falls below normal. Which response restores it?

A person who recovers from measles does not catch measles again, yet still catches other illnesses. What best explains this?

A patient with influenza is prescribed a course of antibiotics and does not improve. Why did the antibiotics fail to help?

The table compares the concentration of three substances in blood plasma and in urine from the same person. What do the glucose figures indicate?

The wall of an alveolus is only one cell thick, which speeds the diffusion of gases between the air and the blood.

A person eats bread containing starch. Which sequence describes what happens to that starch?

A student touches a hot pan and jerks a hand back instantly, then feels shaky for several minutes afterward. Which pairing best explains the two responses?

The diagram shows how a human protein is made using bacteria. What is the role of the bacterium in this process?

Two children of the same parents differ from each other in many inherited traits. Which processes best account for this variation?

In guinea pigs, black coat is dominant over white. Two black guinea pigs, each heterozygous for coat color, are crossed. What proportion of their offspring is expected to be white?

A trait caused by a dominant allele is found in only 8 percent of a large population. What does this show?

A mutation occurs in a skin cell of an adult. Which statement about this mutation is correct?

Nerve cells and muscle cells in one person contain the same DNA, yet they differ in structure and function. What best explains this difference?

A farmer crosses the highest-yielding wheat plants over many generations. A laboratory instead inserts a bacterial gene into wheat cells. How do the two methods differ?

The diagram shows an ocean food web. How much of the energy stored by the algae reaches the seal, and why?

The diagram shows how carbon moves through a forest ecosystem. A large area of the forest is cleared and the timber burned. What is the most likely effect?

The graph shows the percentage of bacterial samples in one hospital that survived treatment with a particular antibiotic. Which explanation best accounts for the trend?

Over 20 years, a beetle population living on soot-stained trees became mostly dark colored. Which statement describes how this change happened?

Homologous structures such as the forelimbs of a whale, a bat and a human are evidence that those species share a common ancestor.

Zebra mussels carried into a lake on boat hulls spread rapidly, and the native mussels decline. Which factor best explains the rapid spread of the introduced species?

Energy is recycled through an ecosystem in the same way that carbon is.

Barnacles attach to the skin of a whale, where they gain transport and better access to food, while the whale is neither helped nor harmed. Which relationship is this?

Deer released on an island increase quickly for several years, then level off and stay near 300 animals for a decade. What is the best explanation for the leveling off?

Burning coal releases sulfur and nitrogen oxides into the atmosphere. What effect do these gases have on lakes downwind?